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Overview
Comment:Modify the fts5 leaf page format to permit faster seek operations. This is a file-format change. Any existing databases can be upgraded by running the fts5 'rebuild' command.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 0c0c4ae971e54efc526eed7bd071c90dfadb95ff
User & Date: dan 2015-09-10 17:23:37
Context
2015-09-10
19:22
Fix a potential NULL pointer deref in the testing logic of pcache1. NB: The -DSQLITE_TEST compile-time option is needed to hit the problem. check-in: f5580f08 user: drh tags: trunk
17:23
Modify the fts5 leaf page format to permit faster seek operations. This is a file-format change. Any existing databases can be upgraded by running the fts5 'rebuild' command. check-in: 0c0c4ae9 user: dan tags: trunk
17:20
Create separate "path" and "root" columns in the json_each() and json_tree() virtual tables. "Root" is the 2nd parameter and is fixed. "Path" varies as json_tree() walks the hierarchy. check-in: 127cce3e user: drh tags: trunk
16:39
Increment the fts5 version value to indicate that the on-disk format has changed. Closed-Leaf check-in: 99de5e36 user: dan tags: fts5-incompatible
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to ext/fts5/fts5Int.h.

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**   This exists in order to allow the fts5_index.c module to return a 
**   decent error message if it encounters a file-format version it does
**   not understand.
**
** bColumnsize:
**   True if the %_docsize table is created.
**






*/
struct Fts5Config {
  sqlite3 *db;                    /* Database handle */
  char *zDb;                      /* Database holding FTS index (e.g. "main") */
  char *zName;                    /* Name of FTS index */
  int nCol;                       /* Number of columns */
  char **azCol;                   /* Column names */
................................................................................
  int nAutomerge;                 /* 'automerge' setting */
  int nCrisisMerge;               /* Maximum allowed segments per level */
  char *zRank;                    /* Name of rank function */
  char *zRankArgs;                /* Arguments to rank function */

  /* If non-NULL, points to sqlite3_vtab.base.zErrmsg. Often NULL. */
  char **pzErrmsg;




};

/* Current expected value of %_config table 'version' field */
#define FTS5_CURRENT_VERSION 3

#define FTS5_CONTENT_NORMAL   0
#define FTS5_CONTENT_NONE     1
#define FTS5_CONTENT_EXTERNAL 2










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**   This exists in order to allow the fts5_index.c module to return a 
**   decent error message if it encounters a file-format version it does
**   not understand.
**
** bColumnsize:
**   True if the %_docsize table is created.
**
** bPrefixIndex:
**   This is only used for debugging. If set to false, any prefix indexes
**   are ignored. This value is configured using:
**
**       INSERT INTO tbl(tbl, rank) VALUES('prefix-index', $bPrefixIndex);
**
*/
struct Fts5Config {
  sqlite3 *db;                    /* Database handle */
  char *zDb;                      /* Database holding FTS index (e.g. "main") */
  char *zName;                    /* Name of FTS index */
  int nCol;                       /* Number of columns */
  char **azCol;                   /* Column names */
................................................................................
  int nAutomerge;                 /* 'automerge' setting */
  int nCrisisMerge;               /* Maximum allowed segments per level */
  char *zRank;                    /* Name of rank function */
  char *zRankArgs;                /* Arguments to rank function */

  /* If non-NULL, points to sqlite3_vtab.base.zErrmsg. Often NULL. */
  char **pzErrmsg;

#ifdef SQLITE_DEBUG
  int bPrefixIndex;               /* True to use prefix-indexes */
#endif
};

/* Current expected value of %_config table 'version' field */
#define FTS5_CURRENT_VERSION 4

#define FTS5_CONTENT_NORMAL   0
#define FTS5_CONTENT_NONE     1
#define FTS5_CONTENT_EXTERNAL 2



Changes to ext/fts5/fts5_buffer.c.

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*/



#include "fts5Int.h"

int sqlite3Fts5BufferGrow(int *pRc, Fts5Buffer *pBuf, int nByte){
  /* A no-op if an error has already occurred */
  if( *pRc ) return 1;

  if( (pBuf->n + nByte) > pBuf->nSpace ){
    u8 *pNew;
    int nNew = pBuf->nSpace ? pBuf->nSpace*2 : 64;




    while( nNew<(pBuf->n + nByte) ){
      nNew = nNew * 2;
    }
    pNew = sqlite3_realloc(pBuf->p, nNew);
    if( pNew==0 ){
      *pRc = SQLITE_NOMEM;
      return 1;







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*/



#include "fts5Int.h"

int sqlite3Fts5BufferGrow(int *pRc, Fts5Buffer *pBuf, int nByte){



  if( (pBuf->n + nByte) > pBuf->nSpace ){
    u8 *pNew;
    int nNew = pBuf->nSpace ? pBuf->nSpace*2 : 64;

    /* A no-op if an error has already occurred */
    if( *pRc ) return 1;

    while( nNew<(pBuf->n + nByte) ){
      nNew = nNew * 2;
    }
    pNew = sqlite3_realloc(pBuf->p, nNew);
    if( pNew==0 ){
      *pRc = SQLITE_NOMEM;
      return 1;

Changes to ext/fts5/fts5_config.c.

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  nByte = nArg * (sizeof(char*) + sizeof(u8));
  pRet->azCol = (char**)sqlite3Fts5MallocZero(&rc, nByte);
  pRet->abUnindexed = (u8*)&pRet->azCol[nArg];
  pRet->zDb = sqlite3Fts5Strndup(&rc, azArg[1], -1);
  pRet->zName = sqlite3Fts5Strndup(&rc, azArg[2], -1);
  pRet->bColumnsize = 1;



  if( rc==SQLITE_OK && sqlite3_stricmp(pRet->zName, FTS5_RANK_NAME)==0 ){
    *pzErr = sqlite3_mprintf("reserved fts5 table name: %s", pRet->zName);
    rc = SQLITE_ERROR;
  }

  for(i=3; rc==SQLITE_OK && i<nArg; i++){
    const char *zOrig = azArg[i];







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  nByte = nArg * (sizeof(char*) + sizeof(u8));
  pRet->azCol = (char**)sqlite3Fts5MallocZero(&rc, nByte);
  pRet->abUnindexed = (u8*)&pRet->azCol[nArg];
  pRet->zDb = sqlite3Fts5Strndup(&rc, azArg[1], -1);
  pRet->zName = sqlite3Fts5Strndup(&rc, azArg[2], -1);
  pRet->bColumnsize = 1;
#ifdef SQLITE_DEBUG
  pRet->bPrefixIndex = 1;
#endif
  if( rc==SQLITE_OK && sqlite3_stricmp(pRet->zName, FTS5_RANK_NAME)==0 ){
    *pzErr = sqlite3_mprintf("reserved fts5 table name: %s", pRet->zName);
    rc = SQLITE_ERROR;
  }

  for(i=3; rc==SQLITE_OK && i<nArg; i++){
    const char *zOrig = azArg[i];

Changes to ext/fts5/fts5_index.c.

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4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
....
4389
4390
4391
4392
4393
4394
4395





4396
4397
4398
4399
4400
4401
4402
4403
....
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
....
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
....
4766
4767
4768
4769
4770
4771
4772
4773






4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784

4785
4786
4787
4788
4789
4790
4791
....
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831



















































4832
4833
4834
4835
4836
4837
4838
....
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875

4876
4877
4878
4879

4880
4881
4882
4883
4884
4885
4886
4887
4888


4889
4890
4891
4892
4893
4894
4895
....
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931

4932
4933
4934
4935
4936
4937
4938
4939
....
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
....
5189
5190
5191
5192
5193
5194
5195

5196
5197

5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
....
5227
5228
5229
5230
5231
5232
5233




5234
5235
5236
5237
5238
5239
5240


5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
....
5260
5261
5262
5263
5264
5265
5266
5267



5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280





5281
5282


5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293



5294
5295




5296
5297




5298

5299





5300
5301


5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
....
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
**
**   Then, for each level from 0 to nMax:
**
**     + number of input segments in ongoing merge.
**     + total number of segments in level.
**     + for each segment from oldest to newest:
**         + segment id (always > 0)
**         + b-tree height (1 -> root is leaf, 2 -> root is parent of leaf etc.)
**         + first leaf page number (often 1, always greater than 0)
**         + final leaf page number
**
** 2. The Averages Record:
**
**   A single record within the %_data table. The data is a list of varints.
**   The first value is the number of rows in the index. Then, for each column
**   from left to right, the total number of tokens in the column for all 
**   rows of the table.
**
** 3. Segment leaves:
**
**   TERM DOCLIST FORMAT:
**
**     Most of each segment leaf is taken up by term/doclist data. The 
**     general format of the term/doclist data is:

**
**         varint : size of first term
**         blob:    first term data
**         doclist: first doclist
**         zero-or-more {
**           varint:  number of bytes in common with previous term
**           varint:  number of bytes of new term data (nNew)
................................................................................
**
**         varint:  first rowid
**         poslist: first poslist
**         zero-or-more {
**           varint:  rowid delta (always > 0)
**           poslist: next poslist
**         }
**         0x00 byte
**
**     poslist format:
**
**         varint: size of poslist in bytes multiplied by 2, not including
**                 this field. Plus 1 if this entry carries the "delete" flag.
**         collist: collist for column 0
**         zero-or-more {
................................................................................
**     collist format:
**
**         varint: first offset + 2
**         zero-or-more {
**           varint: offset delta + 2
**         }
**
**   PAGINATION
**
**     The format described above is only accurate if the entire term/doclist

















**     data fits on a single leaf page. If this is not the case, the format
**     is changed in two ways:
**
**       + if the first rowid on a page occurs before the first term, it
**         is stored as a literal value:
**
**             varint:  first rowid
**
**       + the first term on each page is stored in the same way as the
**         very first term of the segment:
**
**             varint : size of first term
**             blob:    first term data
**
**     Each leaf page begins with:
**
**       + 2-byte unsigned containing offset to first rowid (or 0).
**       + 2-byte unsigned containing offset to first term (or 0).
**
**   Followed by term/doclist data.
**
** 4. Segment interior nodes:
**
**   The interior nodes turn the list of leaves into a b+tree. 
**
**   Each interior node begins with a varint - the page number of the left
**   most child node. Following this, for each leaf page except the first,
**   the interior nodes contain:
**
**     a) If the leaf page contains at least one term, then a term-prefix that
**        is greater than all previous terms, and less than or equal to the
**        first term on the leaf page.
**
**     b) If the leaf page no terms, a record indicating how many consecutive
**        leaves contain no terms, and whether or not there is an associated
**        by-rowid index record.
**
**   By definition, there is never more than one type (b) record in a row.
**   Type (b) records only ever appear on height=1 pages - immediate parents
**   of leaves. Only type (a) records are pushed to higher levels.
**
**   Term format:
**
**     * Number of bytes in common with previous term plus 2, as a varint.
**     * Number of bytes of new term data, as a varint.
**     * new term data.
**
**   No-term format:
**
**     * either an 0x00 or 0x01 byte. If the value 0x01 is used, then there 
**       is an associated index-by-rowid record.
**     * the number of zero-term leaves as a varint.
**
** 5. Segment doclist indexes:
**
**   Doclist indexes are themselves b-trees, however they usually consist of
**   a single leaf record only. The format of each doclist index leaf page 
**   is:
**
**     * Flags byte. Bits are:
................................................................................
/*
** Rowids for the averages and structure records in the %_data table.
*/
#define FTS5_AVERAGES_ROWID     1    /* Rowid used for the averages record */
#define FTS5_STRUCTURE_ROWID   10    /* The structure record */

/*
** Macros determining the rowids used by segment nodes. All nodes in all
** segments for all indexes (the regular FTS index and any prefix indexes)
** are stored in the %_data table with large positive rowids.

**
** The %_data table may contain up to (1<<FTS5_SEGMENT_INDEX_BITS) 
** indexes - one regular term index and zero or more prefix indexes.
**

** Each segment in an index has a unique id greater than zero.
**
** Each node in a segment b-tree is assigned a "page number" that is unique
** within nodes of its height within the segment (leaf nodes have a height 
** of 0, parents 1, etc.). Page numbers are allocated sequentially so that
** a nodes page number is always one more than its left sibling.
**
** The rowid for a node is then found using the FTS5_SEGMENT_ROWID() macro
** below. The FTS5_SEGMENT_*_BITS macros define the number of bits used
** to encode the three FTS5_SEGMENT_ROWID() arguments. This module returns
** SQLITE_FULL and fails the current operation if they ever prove too small.
*/
#define FTS5_DATA_ID_B     16     /* Max seg id number 65535 */
#define FTS5_DATA_DLI_B     1     /* Doclist-index flag (1 bit) */
#define FTS5_DATA_HEIGHT_B  5     /* Max b-tree height of 32 */
#define FTS5_DATA_PAGE_B   31     /* Max page number of 2147483648 */

#define fts5_dri(segid, dlidx, height, pgno) (                                 \
 ((i64)(segid)  << (FTS5_DATA_PAGE_B+FTS5_DATA_HEIGHT_B+FTS5_DATA_DLI_B)) +    \
 ((i64)(dlidx)  << (FTS5_DATA_PAGE_B + FTS5_DATA_HEIGHT_B)) +                  \
 ((i64)(height) << (FTS5_DATA_PAGE_B)) +                                       \
 ((i64)(pgno))                                                                 \
)

#define FTS5_SEGMENT_ROWID(segid, height, pgno) fts5_dri(segid, 0, height, pgno)
#define FTS5_DLIDX_ROWID(segid, height, pgno)   fts5_dri(segid, 1, height, pgno)

/*
** Maximum segments permitted in a single index 
*/
#define FTS5_MAX_SEGMENT 2000

#ifdef SQLITE_DEBUG
................................................................................
typedef struct Fts5SegWriter Fts5SegWriter;
typedef struct Fts5Structure Fts5Structure;
typedef struct Fts5StructureLevel Fts5StructureLevel;
typedef struct Fts5StructureSegment Fts5StructureSegment;

struct Fts5Data {
  u8 *p;                          /* Pointer to buffer containing record */
  int n;                          /* Size of record in bytes */

};

/*
** One object per %_data table.
*/
struct Fts5Index {
  Fts5Config *pConfig;            /* Virtual table configuration */
................................................................................
/*
** The contents of the "structure" record for each index are represented
** using an Fts5Structure record in memory. Which uses instances of the 
** other Fts5StructureXXX types as components.
*/
struct Fts5StructureSegment {
  int iSegid;                     /* Segment id */
  int nHeight;                    /* Height of segment b-tree */
  int pgnoFirst;                  /* First leaf page number in segment */
  int pgnoLast;                   /* Last leaf page number in segment */
};
struct Fts5StructureLevel {
  int nMerge;                     /* Number of segments in incr-merge */
  int nSeg;                       /* Total number of segments on level */
  Fts5StructureSegment *aSeg;     /* Array of segments. aSeg[0] is oldest. */
................................................................................
};

/*
** An object of type Fts5SegWriter is used to write to segments.
*/
struct Fts5PageWriter {
  int pgno;                       /* Page number for this page */

  Fts5Buffer buf;                 /* Buffer containing page data */

  Fts5Buffer term;                /* Buffer containing previous term on page */
};
struct Fts5DlidxWriter {
  int pgno;                       /* Page number for this page */
  int bPrevValid;                 /* True if iPrev is valid */
  i64 iPrev;                      /* Previous rowid value written to page */
  Fts5Buffer buf;                 /* Buffer containing page data */
................................................................................
};
struct Fts5SegWriter {
  int iSegid;                     /* Segid to write to */
  Fts5PageWriter writer;          /* PageWriter object */
  i64 iPrevRowid;                 /* Previous rowid written to current leaf */
  u8 bFirstRowidInDoclist;        /* True if next rowid is first in doclist */
  u8 bFirstRowidInPage;           /* True if next rowid is first in page */

  u8 bFirstTermInPage;            /* True if next term will be first in leaf */
  int nLeafWritten;               /* Number of leaf pages written */
  int nEmpty;                     /* Number of contiguous term-less nodes */

  int nDlidx;                     /* Allocated size of aDlidx[] array */
  Fts5DlidxWriter *aDlidx;        /* Array of Fts5DlidxWriter objects */

................................................................................
**
** iRowidOffset/nRowidOffset/aRowidOffset:
**     These are used if the FTS5_SEGITER_REVERSE flag is set.
**
**     For each rowid on the page corresponding to the current term, the
**     corresponding aRowidOffset[] entry is set to the byte offset of the
**     start of the "position-list-size" field within the page.



*/
struct Fts5SegIter {
  Fts5StructureSegment *pSeg;     /* Segment to iterate through */
  int flags;                      /* Mask of configuration flags */
  int iLeafPgno;                  /* Current leaf page number */
  Fts5Data *pLeaf;                /* Current leaf data */
  Fts5Data *pNextLeaf;            /* Leaf page (iLeafPgno+1) */
  int iLeafOffset;                /* Byte offset within current leaf */

  /* The page and offset from which the current term was read. The offset 
  ** is the offset of the first rowid in the current doclist.  */
  int iTermLeafPgno;
  int iTermLeafOffset;




  /* The following are only used if the FTS5_SEGITER_REVERSE flag is set. */
  int iRowidOffset;               /* Current entry in aRowidOffset[] */
  int nRowidOffset;               /* Allocated size of aRowidOffset[] array */
  int *aRowidOffset;              /* Array of offset to rowid fields */

  Fts5DlidxIter *pDlidx;          /* If there is a doclist-index */
................................................................................

  /* Variables populated based on current entry. */
  Fts5Buffer term;                /* Current term */
  i64 iRowid;                     /* Current rowid */
  int nPos;                       /* Number of bytes in current position list */
  int bDel;                       /* True if the delete flag is set */
};









#define FTS5_SEGITER_ONETERM 0x01
#define FTS5_SEGITER_REVERSE 0x02













/*
** poslist:
**   Used by sqlite3Fts5IterPoslist() when the poslist needs to be buffered.
**   There is no way to tell if this is populated or not.
*/
struct Fts5IndexIter {
  Fts5Index *pIndex;              /* Index that owns this iterator */
................................................................................
){
  int nCmp = MIN(nLeft, nRight);
  int res = memcmp(pLeft, pRight, nCmp);
  return (res==0 ? (nLeft - nRight) : res);
}
#endif







/*
** Close the read-only blob handle, if it is open.
*/
static void fts5CloseReader(Fts5Index *p){
  if( p->pReader ){
    sqlite3_blob *pReader = p->pReader;
................................................................................

    if( rc==SQLITE_OK ){
      u8 *aOut = 0;               /* Read blob data into this buffer */
      int nByte = sqlite3_blob_bytes(p->pReader);
      int nAlloc = sizeof(Fts5Data) + nByte + FTS5_DATA_PADDING;
      pRet = (Fts5Data*)sqlite3_malloc(nAlloc);
      if( pRet ){
        pRet->n = nByte;
        aOut = pRet->p = (u8*)&pRet[1];
      }else{
        rc = SQLITE_NOMEM;
      }

      if( rc==SQLITE_OK ){
        rc = sqlite3_blob_read(p->pReader, aOut, nByte, 0);
      }
      if( rc!=SQLITE_OK ){
        sqlite3_free(pRet);
        pRet = 0;



      }
    }
    p->rc = rc;
    p->nRead++;
  }

  assert( (pRet==0)==(p->rc!=SQLITE_OK) );
................................................................................
  p->rc = sqlite3_reset(p->pDeleter);
}

/*
** Remove all records associated with segment iSegid.
*/
static void fts5DataRemoveSegment(Fts5Index *p, int iSegid){
  i64 iFirst = FTS5_SEGMENT_ROWID(iSegid, 0, 0);
  i64 iLast = FTS5_SEGMENT_ROWID(iSegid+1, 0, 0)-1;
  fts5DataDelete(p, iFirst, iLast);
  if( p->pIdxDeleter==0 ){
    Fts5Config *pConfig = p->pConfig;
    fts5IndexPrepareStmt(p, &p->pIdxDeleter, sqlite3_mprintf(
          "DELETE FROM '%q'.'%q_idx' WHERE segid=?",
          pConfig->zDb, pConfig->zName
    ));
................................................................................
          nTotal * sizeof(Fts5StructureSegment)
      );

      if( rc==SQLITE_OK ){
        pLvl->nSeg = nTotal;
        for(iSeg=0; iSeg<nTotal; iSeg++){
          i += fts5GetVarint32(&pData[i], pLvl->aSeg[iSeg].iSegid);
          i += fts5GetVarint32(&pData[i], pLvl->aSeg[iSeg].nHeight);
          i += fts5GetVarint32(&pData[i], pLvl->aSeg[iSeg].pgnoFirst);
          i += fts5GetVarint32(&pData[i], pLvl->aSeg[iSeg].pgnoLast);
        }
      }else{
        fts5StructureRelease(pRet);
        pRet = 0;
      }
................................................................................
  Fts5Structure *pRet = 0;        /* Object to return */
  int iCookie;                    /* Configuration cookie */
  Fts5Data *pData;
  Fts5Buffer buf = {0, 0, 0};

  pData = fts5DataRead(p, FTS5_STRUCTURE_ROWID);
  if( p->rc ) return 0;

  memset(&pData->p[pData->n], 0, FTS5_DATA_PADDING);
  p->rc = fts5StructureDecode(pData->p, pData->n, &iCookie, &pRet);
  if( p->rc==SQLITE_OK && pConfig->iCookie!=iCookie ){
    p->rc = sqlite3Fts5ConfigLoad(pConfig, iCookie);
  }

  fts5DataRelease(pData);
  if( p->rc!=SQLITE_OK ){
    fts5StructureRelease(pRet);
................................................................................
      Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
      fts5BufferAppendVarint(&p->rc, &buf, pLvl->nMerge);
      fts5BufferAppendVarint(&p->rc, &buf, pLvl->nSeg);
      assert( pLvl->nMerge<=pLvl->nSeg );

      for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
        fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].iSegid);
        fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].nHeight);
        fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].pgnoFirst);
        fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].pgnoLast);
      }
    }

    fts5DataWrite(p, FTS5_STRUCTURE_ROWID, buf.p, buf.n);
    fts5BufferFree(&buf);
................................................................................
){
  if( p->rc==SQLITE_OK ){
    int iTst;
    int iPromote = -1;
    int szPromote = 0;            /* Promote anything this size or smaller */
    Fts5StructureSegment *pSeg;   /* Segment just written */
    int szSeg;                    /* Size of segment just written */




    pSeg = &pStruct->aLevel[iLvl].aSeg[pStruct->aLevel[iLvl].nSeg-1];
    szSeg = (1 + pSeg->pgnoLast - pSeg->pgnoFirst);

    /* Check for condition (a) */
    for(iTst=iLvl-1; iTst>=0 && pStruct->aLevel[iTst].nSeg==0; iTst--);
    if( iTst>=0 ){
      int i;
................................................................................
    assert( pLvl->bEof==0 );
    pLvl->iOff = 1;
    pLvl->iOff += fts5GetVarint32(&pData->p[1], pLvl->iLeafPgno);
    pLvl->iOff += fts5GetVarint(&pData->p[pLvl->iOff], (u64*)&pLvl->iRowid);
    pLvl->iFirstOff = pLvl->iOff;
  }else{
    int iOff;
    for(iOff=pLvl->iOff; iOff<pData->n; iOff++){
      if( pData->p[iOff] ) break; 
    }

    if( iOff<pData->n ){
      i64 iVal;
      pLvl->iLeafPgno += (iOff - pLvl->iOff) + 1;
      iOff += fts5GetVarint(&pData->p[iOff], (u64*)&iVal);
      pLvl->iRowid += iVal;
      pLvl->iOff = iOff;
    }else{
      pLvl->bEof = 1;
................................................................................
/*
** Load the next leaf page into the segment iterator.
*/
static void fts5SegIterNextPage(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5SegIter *pIter              /* Iterator to advance to next page */
){

  Fts5StructureSegment *pSeg = pIter->pSeg;
  fts5DataRelease(pIter->pLeaf);
  pIter->iLeafPgno++;
  if( pIter->pNextLeaf ){
    assert( pIter->iLeafPgno<=pSeg->pgnoLast );
    pIter->pLeaf = pIter->pNextLeaf;
    pIter->pNextLeaf = 0;
  }else if( pIter->iLeafPgno<=pSeg->pgnoLast ){
    pIter->pLeaf = fts5DataRead(p, 
        FTS5_SEGMENT_ROWID(pSeg->iSegid, 0, pIter->iLeafPgno)
    );
  }else{
    pIter->pLeaf = 0;












  }
}

/*
** Argument p points to a buffer containing a varint to be interpreted as a
** position list size field. Read the varint and return the number of bytes
** read. Before returning, set *pnSz to the number of bytes in the position
................................................................................
**
** Leave Fts5SegIter.iLeafOffset pointing to the first byte of the 
** position list content (if any).
*/
static void fts5SegIterLoadNPos(Fts5Index *p, Fts5SegIter *pIter){
  if( p->rc==SQLITE_OK ){
    int iOff = pIter->iLeafOffset;  /* Offset to read at */

    if( iOff>=pIter->pLeaf->n ){
      p->rc = FTS5_CORRUPT;
    }else{
      const u8 *a = &pIter->pLeaf->p[iOff];
      pIter->iLeafOffset += fts5GetPoslistSize(a, &pIter->nPos, &pIter->bDel);
    }
  }
}

static void fts5SegIterLoadRowid(Fts5Index *p, Fts5SegIter *pIter){
  u8 *a = pIter->pLeaf->p;        /* Buffer to read data from */
  int iOff = pIter->iLeafOffset;


  if( iOff>=pIter->pLeaf->n ){
    fts5SegIterNextPage(p, pIter);
    if( pIter->pLeaf==0 ){
      if( p->rc==SQLITE_OK ) p->rc = FTS5_CORRUPT;
      return;
    }
    iOff = 4;
    a = pIter->pLeaf->p;
................................................................................
  iOff += fts5GetVarint32(&a[iOff], nNew);
  pIter->term.n = nKeep;
  fts5BufferAppendBlob(&p->rc, &pIter->term, nNew, &a[iOff]);
  iOff += nNew;
  pIter->iTermLeafOffset = iOff;
  pIter->iTermLeafPgno = pIter->iLeafPgno;
  pIter->iLeafOffset = iOff;









  fts5SegIterLoadRowid(p, pIter);
}

/*
** Initialize the iterator object pIter to iterate through the entries in
** segment pSeg. The iterator is left pointing to the first entry when 
................................................................................
    memset(pIter, 0, sizeof(*pIter));
    pIter->pSeg = pSeg;
    pIter->iLeafPgno = pSeg->pgnoFirst-1;
    fts5SegIterNextPage(p, pIter);
  }

  if( p->rc==SQLITE_OK ){
    u8 *a = pIter->pLeaf->p;
    pIter->iLeafOffset = fts5GetU16(&a[2]);



    fts5SegIterLoadTerm(p, pIter, 0);
    fts5SegIterLoadNPos(p, pIter);
  }
}

/*
** This function is only ever called on iterators created by calls to
................................................................................
** This function advances the iterator so that it points to the last 
** relevant rowid on the page and, if necessary, initializes the 
** aRowidOffset[] and iRowidOffset variables. At this point the iterator
** is in its regular state - Fts5SegIter.iLeafOffset points to the first
** byte of the position list content associated with said rowid.
*/
static void fts5SegIterReverseInitPage(Fts5Index *p, Fts5SegIter *pIter){
  int n = pIter->pLeaf->n;
  int i = pIter->iLeafOffset;
  u8 *a = pIter->pLeaf->p;
  int iRowidOffset = 0;






  while( 1 ){
    i64 iDelta = 0;
    int nPos;
    int bDummy;

    i += fts5GetPoslistSize(&a[i], &nPos, &bDummy);
    i += nPos;
    if( i>=n ) break;
    i += fts5GetVarint(&a[i], (u64*)&iDelta);
    if( iDelta==0 ) break;
    pIter->iRowid += iDelta;

    if( iRowidOffset>=pIter->nRowidOffset ){
      int nNew = pIter->nRowidOffset + 8;
      int *aNew = (int*)sqlite3_realloc(pIter->aRowidOffset, nNew*sizeof(int));
      if( aNew==0 ){
        p->rc = SQLITE_NOMEM;
................................................................................

  fts5DataRelease(pIter->pLeaf);
  pIter->pLeaf = 0;
  while( p->rc==SQLITE_OK && pIter->iLeafPgno>pIter->iTermLeafPgno ){
    Fts5Data *pNew;
    pIter->iLeafPgno--;
    pNew = fts5DataRead(p, FTS5_SEGMENT_ROWID(
          pIter->pSeg->iSegid, 0, pIter->iLeafPgno
    ));
    if( pNew ){
      if( pIter->iLeafPgno==pIter->iTermLeafPgno ){
        if( pIter->iTermLeafOffset<pNew->n ){
          pIter->pLeaf = pNew;
          pIter->iLeafOffset = pIter->iTermLeafOffset;
        }
      }else{
        int iRowidOff, dummy;
        fts5LeafHeader(pNew, &iRowidOff, &dummy);
        if( iRowidOff ){
          pIter->pLeaf = pNew;
          pIter->iLeafOffset = iRowidOff;
        }
      }

      if( pIter->pLeaf ){
................................................................................
      }else{
        fts5DataRelease(pNew);
      }
    }
  }

  if( pIter->pLeaf ){

    fts5SegIterReverseInitPage(p, pIter);
  }
}

/*
** Return true if the iterator passed as the second argument currently
** points to a delete marker. A delete marker is an entry with a 0 byte
................................................................................
      Fts5Data *pLeaf = pIter->pLeaf;
      int iOff;
      int bNewTerm = 0;
      int nKeep = 0;

      /* Search for the end of the position list within the current page. */
      u8 *a = pLeaf->p;
      int n = pLeaf->n;


      iOff = pIter->iLeafOffset + pIter->nPos;

      if( iOff<n ){
        /* The next entry is on the current page */
        u64 iDelta;
        iOff += sqlite3Fts5GetVarint(&a[iOff], &iDelta);
        pIter->iLeafOffset = iOff;
        if( iDelta==0 ){
          bNewTerm = 1;
          if( iOff>=n ){
            fts5SegIterNextPage(p, pIter);
            pIter->iLeafOffset = 4;
          }else if( iOff!=fts5GetU16(&a[2]) ){
            pIter->iLeafOffset += fts5GetVarint32(&a[iOff], nKeep);
          }
        }else{


          pIter->iRowid += iDelta;

        }


      }else if( pIter->pSeg==0 ){
        const u8 *pList = 0;
        const char *zTerm = 0;
        int nList = 0;
        if( 0==(pIter->flags & FTS5_SEGITER_ONETERM) ){
          sqlite3Fts5HashScanNext(p->pHash);
          sqlite3Fts5HashScanEntry(p->pHash, &zTerm, &pList, &nList);
        }
        if( pList==0 ){
          fts5DataRelease(pIter->pLeaf);
          pIter->pLeaf = 0;
        }else{
          pIter->pLeaf->p = (u8*)pList;
          pIter->pLeaf->n = nList;


          sqlite3Fts5BufferSet(&p->rc, &pIter->term, strlen(zTerm), (u8*)zTerm);
          pIter->iLeafOffset = fts5GetVarint(pList, (u64*)&pIter->iRowid);
        }
      }else{
        iOff = 0;
        /* Next entry is not on the current page */
        while( iOff==0 ){
          fts5SegIterNextPage(p, pIter);
          pLeaf = pIter->pLeaf;
          if( pLeaf==0 ) break;
          if( (iOff = fts5GetU16(&pLeaf->p[0])) && iOff<pLeaf->n ){

            iOff += sqlite3Fts5GetVarint(&pLeaf->p[iOff], (u64*)&pIter->iRowid);
            pIter->iLeafOffset = iOff;
          }
          else if( (iOff = fts5GetU16(&pLeaf->p[2])) ){











            pIter->iLeafOffset = iOff;

            bNewTerm = 1;
          }
          if( iOff>=pLeaf->n ){
            p->rc = FTS5_CORRUPT;
            return;
          }
        }
      }

      /* Check if the iterator is now at EOF. If so, return early. */
      if( pIter->pLeaf ){
        if( bNewTerm ){
          if( pIter->flags & FTS5_SEGITER_ONETERM ){
            fts5DataRelease(pIter->pLeaf);
            pIter->pLeaf = 0;
          }else{

            fts5SegIterLoadTerm(p, pIter, nKeep);
            fts5SegIterLoadNPos(p, pIter);
            if( pbNewTerm ) *pbNewTerm = 1;
          }
        }else{
          fts5SegIterLoadNPos(p, pIter);
        }
................................................................................
  Fts5DlidxIter *pDlidx = pIter->pDlidx;
  Fts5Data *pLast = 0;
  int pgnoLast = 0;

  if( pDlidx ){
    int iSegid = pIter->pSeg->iSegid;
    pgnoLast = fts5DlidxIterPgno(pDlidx);
    pLast = fts5DataRead(p, FTS5_SEGMENT_ROWID(iSegid, 0, pgnoLast));
  }else{
    int iOff;                               /* Byte offset within pLeaf */
    Fts5Data *pLeaf = pIter->pLeaf;         /* Current leaf data */

    /* Currently, Fts5SegIter.iLeafOffset (and iOff) points to the first 
    ** byte of position-list content for the current rowid. Back it up
    ** so that it points to the start of the position-list size field. */
    pIter->iLeafOffset -= sqlite3Fts5GetVarintLen(pIter->nPos*2+pIter->bDel);
    iOff = pIter->iLeafOffset;
    assert( iOff>=4 );

    /* Search for a new term within the current leaf. If one can be found,
    ** then this page contains the largest rowid for the current term. */
    while( iOff<pLeaf->n ){
      int nPos;
      i64 iDelta;
      int bDummy;

      /* Read the position-list size field */
      iOff += fts5GetPoslistSize(&pLeaf->p[iOff], &nPos, &bDummy);
      iOff += nPos;
      if( iOff>=pLeaf->n ) break;

      /* Rowid delta. Or, if 0x00, the end of doclist marker. */
      nPos = fts5GetVarint(&pLeaf->p[iOff], (u64*)&iDelta);
      if( iDelta==0 ) break;
      iOff += nPos;
    }

    /* If this condition is true then the largest rowid for the current
    ** term may not be stored on the current page. So search forward to
    ** see where said rowid really is.  */
    if( iOff>=pLeaf->n ){
      int pgno;
      Fts5StructureSegment *pSeg = pIter->pSeg;

      /* The last rowid in the doclist may not be on the current page. Search
      ** forward to find the page containing the last rowid.  */
      for(pgno=pIter->iLeafPgno+1; !p->rc && pgno<=pSeg->pgnoLast; pgno++){
        i64 iAbs = FTS5_SEGMENT_ROWID(pSeg->iSegid, 0, pgno);
        Fts5Data *pNew = fts5DataRead(p, iAbs);
        if( pNew ){
          int iRowid, iTerm;
          fts5LeafHeader(pNew, &iRowid, &iTerm);

          if( iRowid ){
            SWAPVAL(Fts5Data*, pNew, pLast);
            pgnoLast = pgno;
          }
          fts5DataRelease(pNew);
          if( iTerm ) break;
        }
      }
    }
  }

  /* If pLast is NULL at this point, then the last rowid for this doclist
  ** lies on the page currently indicated by the iterator. In this case 
................................................................................
  ** field associated with the first relevant rowid on the page.
  **
  ** Or, if pLast is non-NULL, then it is the page that contains the last
  ** rowid. In this case configure the iterator so that it points to the
  ** first rowid on this page.
  */
  if( pLast ){
    int dummy;
    int iOff;
    fts5DataRelease(pIter->pLeaf);
    pIter->pLeaf = pLast;
    pIter->iLeafPgno = pgnoLast;
    fts5LeafHeader(pLast, &iOff, &dummy);
    iOff += fts5GetVarint(&pLast->p[iOff], (u64*)&pIter->iRowid);
    pIter->iLeafOffset = iOff;







  }

  fts5SegIterReverseInitPage(p, pIter);
}

/*
** Iterator pIter currently points to the first rowid of a doclist.
................................................................................

  assert( pIter->flags & FTS5_SEGITER_ONETERM );
  assert( pIter->pDlidx==0 );

  /* Check if the current doclist ends on this page. If it does, return
  ** early without loading the doclist-index (as it belongs to a different
  ** term. */
  if( pIter->iTermLeafPgno==pIter->iLeafPgno ){
    int iOff = pIter->iLeafOffset + pIter->nPos;
    while( iOff<pLeaf->n ){
      int bDummy;
      int nPos;
      i64 iDelta;

      /* iOff is currently the offset of the start of position list data */
      iOff += fts5GetVarint(&pLeaf->p[iOff], (u64*)&iDelta);
      if( iDelta==0 ) return;
      assert_nc( iOff<pLeaf->n );
      iOff += fts5GetPoslistSize(&pLeaf->p[iOff], &nPos, &bDummy);
      iOff += nPos;
    }
  }

  pIter->pDlidx = fts5DlidxIterInit(p, bRev, iSeg, pIter->iTermLeafPgno);
}

#define fts5IndexGetVarint32(a, iOff, nVal) {     \
  nVal = a[iOff++];                               \
  if( nVal & 0x80 ){                              \
    iOff--;                                       \
    iOff += fts5GetVarint32(&a[iOff], nVal);      \
  }                                               \
}

#define fts5IndexSkipVarint(a, iOff) {            \
  int iEnd = iOff+9;                              \
  while( (a[iOff++] & 0x80) && iOff<iEnd );       \
}
................................................................................
  Fts5Index *p,                   /* Leave any error code here */
  int bGe,                        /* True for a >= search */
  Fts5SegIter *pIter,             /* Iterator to seek */
  const u8 *pTerm, int nTerm      /* Term to search for */
){
  int iOff;
  const u8 *a = pIter->pLeaf->p;

  int n = pIter->pLeaf->n;

  int nMatch = 0;
  int nKeep = 0;
  int nNew = 0;





  assert( p->rc==SQLITE_OK );
  assert( pIter->pLeaf );

  iOff = fts5GetU16(&a[2]);
  if( iOff<4 || iOff>=n ){
    p->rc = FTS5_CORRUPT;
    return;


  }

  while( 1 ){
    int i;
    int nCmp;

    /* Figure out how many new bytes are in this term */
    fts5IndexGetVarint32(a, iOff, nNew);

    if( nKeep<nMatch ){
      goto search_failed;
    }

    assert( nKeep>=nMatch );
    if( nKeep==nMatch ){


      nCmp = MIN(nNew, nTerm-nMatch);
      for(i=0; i<nCmp; i++){
        if( a[iOff+i]!=pTerm[nMatch+i] ) break;
      }
      nMatch += i;

      if( nTerm==nMatch ){
................................................................................
        }else{
          goto search_failed;
        }
      }else if( i<nNew && a[iOff+i]>pTerm[nMatch] ){
        goto search_failed;
      }
    }
    iOff += nNew;


    /* Skip past the doclist. If the end of the page is reached, bail out. */
    while( 1 ){
      int nPos;

      /* Skip past rowid delta */
      fts5IndexSkipVarint(a, iOff);

      /* Skip past position list */
      fts5IndexGetVarint32(a, iOff, nPos);

      iOff += (nPos >> 1);
      if( iOff>=(n-1) ){
        iOff = n;
        goto search_failed;
      }

      /* If this is the end of the doclist, break out of the loop */
      if( a[iOff]==0x00 ){
        iOff++;
        break;
      }
    };

    /* Read the nKeep field of the next term. */
    fts5IndexGetVarint32(a, iOff, nKeep);
  }

 search_failed:
  if( bGe==0 ){
    fts5DataRelease(pIter->pLeaf);
    pIter->pLeaf = 0;
    return;
  }else if( iOff>=n ){
    do {

      fts5SegIterNextPage(p, pIter);
      if( pIter->pLeaf==0 ) return;
      a = pIter->pLeaf->p;
      iOff = fts5GetU16(&a[2]);
      if( iOff ){
        if( iOff<4 || iOff>=n ){
          p->rc = FTS5_CORRUPT;
        }else{
          nKeep = 0;
          iOff += fts5GetVarint32(&a[iOff], nNew);
          break;
        }
      }
    }while( 1 );
  }

 search_success:

  pIter->iLeafOffset = iOff + nNew;
  pIter->iTermLeafOffset = pIter->iLeafOffset;
  pIter->iTermLeafPgno = pIter->iLeafPgno;

  fts5BufferSet(&p->rc, &pIter->term, nKeep, pTerm);
  fts5BufferAppendBlob(&p->rc, &pIter->term, nNew, &a[iOff]);










  fts5SegIterLoadRowid(p, pIter);
  fts5SegIterLoadNPos(p, pIter);
}

/*
** Initialize the object pIter to point to term pTerm/nTerm within segment
** pSeg. If there is no such term in the index, the iterator is set to EOF.
................................................................................

  if( pList ){
    Fts5Data *pLeaf;
    sqlite3Fts5BufferSet(&p->rc, &pIter->term, n, z);
    pLeaf = fts5IdxMalloc(p, sizeof(Fts5Data));
    if( pLeaf==0 ) return;
    pLeaf->p = (u8*)pList;
    pLeaf->n = nList;
    pIter->pLeaf = pLeaf;
    pIter->iLeafOffset = fts5GetVarint(pLeaf->p, (u64*)&pIter->iRowid);


    if( flags & FTS5INDEX_QUERY_DESC ){
      pIter->flags |= FTS5_SEGITER_REVERSE;
      fts5SegIterReverseInitPage(p, pIter);
    }else{
      fts5SegIterLoadNPos(p, pIter);
    }
................................................................................
    pIter->iLeafPgno = iLeafPgno-1;
    fts5SegIterNextPage(p, pIter);
    assert( p->rc!=SQLITE_OK || pIter->iLeafPgno==iLeafPgno );

    if( p->rc==SQLITE_OK ){
      int iOff;
      u8 *a = pIter->pLeaf->p;
      int n = pIter->pLeaf->n;

      iOff = fts5GetU16(&a[0]);
      if( iOff<4 || iOff>=n ){
        p->rc = FTS5_CORRUPT;
      }else{
        iOff += fts5GetVarint(&a[iOff], (u64*)&pIter->iRowid);
        pIter->iLeafOffset = iOff;
        fts5SegIterLoadNPos(p, pIter);
      }
................................................................................
){
  Fts5IndexIter *pNew;
  pNew = fts5MultiIterAlloc(p, 2);
  if( pNew ){
    Fts5SegIter *pIter = &pNew->aSeg[1];

    pIter->flags = FTS5_SEGITER_ONETERM;
    if( pData->n>0 ){
      pIter->pLeaf = pData;
      pIter->iLeafOffset = fts5GetVarint(pData->p, (u64*)&pIter->iRowid);

      pNew->aFirst[1].iFirst = 1;
      if( bDesc ){
        pNew->bRev = 1;
        pIter->flags |= FTS5_SEGITER_REVERSE;
        fts5SegIterReverseInitPage(p, pIter);
      }else{
        fts5SegIterLoadNPos(p, pIter);
................................................................................
  Fts5SegIter *pSeg,              /* Poslist of this iterator */
  void *pCtx,                     /* Context pointer for xChunk callback */
  void (*xChunk)(Fts5Index*, void*, const u8*, int)
){
  int nRem = pSeg->nPos;          /* Number of bytes still to come */
  Fts5Data *pData = 0;
  u8 *pChunk = &pSeg->pLeaf->p[pSeg->iLeafOffset];
  int nChunk = MIN(nRem, pSeg->pLeaf->n - pSeg->iLeafOffset);
  int pgno = pSeg->iLeafPgno;
  int pgnoSave = 0;

  if( (pSeg->flags & FTS5_SEGITER_REVERSE)==0 ){
    pgnoSave = pgno+1;
  }

................................................................................
    xChunk(p, pCtx, pChunk, nChunk);
    nRem -= nChunk;
    fts5DataRelease(pData);
    if( nRem<=0 ){
      break;
    }else{
      pgno++;
      pData = fts5DataRead(p, FTS5_SEGMENT_ROWID(pSeg->pSeg->iSegid, 0, pgno));
      if( pData==0 ) break;
      pChunk = &pData->p[4];
      nChunk = MIN(nRem, pData->n - 4);
      if( pgno==pgnoSave ){
        assert( pSeg->pNextLeaf==0 );
        pSeg->pNextLeaf = pData;
        pData = 0;
      }
    }
  }
................................................................................
}

static void fts5WriteFlushLeaf(Fts5Index *p, Fts5SegWriter *pWriter){
  static const u8 zero[] = { 0x00, 0x00, 0x00, 0x00 };
  Fts5PageWriter *pPage = &pWriter->writer;
  i64 iRowid;







  if( pWriter->bFirstTermInPage ){
    /* No term was written to this page. */
    assert( 0==fts5GetU16(&pPage->buf.p[2]) );

    fts5WriteBtreeNoTerm(p, pWriter);



  }

  /* Write the current page to the db. */
  iRowid = FTS5_SEGMENT_ROWID(pWriter->iSegid, 0, pPage->pgno);
  fts5DataWrite(p, iRowid, pPage->buf.p, pPage->buf.n);

  /* Initialize the next page. */
  fts5BufferZero(&pPage->buf);

  fts5BufferAppendBlob(&p->rc, &pPage->buf, 4, zero);

  pPage->pgno++;

  /* Increase the leaves written counter */
  pWriter->nLeafWritten++;

  /* The new leaf holds no terms or rowids */
  pWriter->bFirstTermInPage = 1;
................................................................................
static void fts5WriteAppendTerm(
  Fts5Index *p, 
  Fts5SegWriter *pWriter,
  int nTerm, const u8 *pTerm 
){
  int nPrefix;                    /* Bytes of prefix compression for term */
  Fts5PageWriter *pPage = &pWriter->writer;

  assert( pPage->buf.n==0 || pPage->buf.n>4 );
  if( pPage->buf.n==0 ){
    /* Zero the first term and first rowid fields */
    static const u8 zero[] = { 0x00, 0x00, 0x00, 0x00 };
    fts5BufferAppendBlob(&p->rc, &pPage->buf, 4, zero);
    assert( pWriter->bFirstTermInPage );
  }
  if( p->rc ) return;
  
  if( pWriter->bFirstTermInPage ){
    /* Update the "first term" field of the page header. */
    assert( pPage->buf.p[2]==0 && pPage->buf.p[3]==0 );
    fts5PutU16(&pPage->buf.p[2], pPage->buf.n);











    nPrefix = 0;
    if( pPage->pgno!=1 ){
      /* This is the first term on a leaf that is not the leftmost leaf in
      ** the segment b-tree. In this case it is necessary to add a term to
      ** the b-tree hierarchy that is (a) larger than the largest term 
      ** already written to the segment and (b) smaller than or equal to
      ** this term. In other words, a prefix of (pTerm/nTerm) that is one
................................................................................
  pWriter->bFirstTermInPage = 0;

  pWriter->bFirstRowidInPage = 0;
  pWriter->bFirstRowidInDoclist = 1;

  assert( p->rc || (pWriter->nDlidx>0 && pWriter->aDlidx[0].buf.n==0) );
  pWriter->aDlidx[0].pgno = pPage->pgno;

  /* If the current leaf page is full, flush it to disk. */
  if( pPage->buf.n>=p->pConfig->pgsz ){
    fts5WriteFlushLeaf(p, pWriter);
  }
}

/*
** Append a rowid and position-list size field to the writers output. 
*/
static void fts5WriteAppendRowid(
  Fts5Index *p, 
  Fts5SegWriter *pWriter,
  i64 iRowid,
  int nPos
){
  if( p->rc==SQLITE_OK ){
    Fts5PageWriter *pPage = &pWriter->writer;





    /* If this is to be the first rowid written to the page, set the 
    ** rowid-pointer in the page-header. Also append a value to the dlidx
    ** buffer, in case a doclist-index is required.  */
    if( pWriter->bFirstRowidInPage ){
      fts5PutU16(pPage->buf.p, pPage->buf.n);
      fts5WriteDlidxAppend(p, pWriter, iRowid);
................................................................................
      fts5BufferAppendVarint(&p->rc, &pPage->buf, iRowid - pWriter->iPrevRowid);
    }
    pWriter->iPrevRowid = iRowid;
    pWriter->bFirstRowidInDoclist = 0;
    pWriter->bFirstRowidInPage = 0;

    fts5BufferAppendVarint(&p->rc, &pPage->buf, nPos);

    if( pPage->buf.n>=p->pConfig->pgsz ){
      fts5WriteFlushLeaf(p, pWriter);
    }
  }
}

static void fts5WriteAppendPoslistData(
  Fts5Index *p, 
  Fts5SegWriter *pWriter, 
  const u8 *aData, 
................................................................................
  int nData
){
  Fts5PageWriter *pPage = &pWriter->writer;
  const u8 *a = aData;
  int n = nData;
  
  assert( p->pConfig->pgsz>0 );
  while( p->rc==SQLITE_OK && (pPage->buf.n + n)>=p->pConfig->pgsz ){


    int nReq = p->pConfig->pgsz - pPage->buf.n;
    int nCopy = 0;
    while( nCopy<nReq ){
      i64 dummy;
      nCopy += fts5GetVarint(&a[nCopy], (u64*)&dummy);
    }
    fts5BufferAppendBlob(&p->rc, &pPage->buf, nCopy, a);
    a += nCopy;
................................................................................
/*
** Flush any data cached by the writer object to the database. Free any
** allocations associated with the writer.
*/
static void fts5WriteFinish(
  Fts5Index *p, 
  Fts5SegWriter *pWriter,         /* Writer object */
  int *pnHeight,                  /* OUT: Height of the b-tree */
  int *pnLeaf                     /* OUT: Number of leaf pages in b-tree */
){
  int i;
  Fts5PageWriter *pLeaf = &pWriter->writer;
  if( p->rc==SQLITE_OK ){
    if( pLeaf->pgno==1 && pLeaf->buf.n==0 ){
      *pnLeaf = 0;
      *pnHeight = 0;
    }else{
      if( pLeaf->buf.n>4 ){
        fts5WriteFlushLeaf(p, pWriter);
      }
      *pnLeaf = pLeaf->pgno-1;

      fts5WriteFlushBtree(p, pWriter);
      *pnHeight = 0;
    }
  }
  fts5BufferFree(&pLeaf->term);
  fts5BufferFree(&pLeaf->buf);

  fts5BufferFree(&pWriter->btterm);

  for(i=0; i<pWriter->nDlidx; i++){
    sqlite3Fts5BufferFree(&pWriter->aDlidx[i].buf);
  }
  sqlite3_free(pWriter->aDlidx);
}

static void fts5WriteInit(
  Fts5Index *p, 
  Fts5SegWriter *pWriter, 
  int iSegid
){


  memset(pWriter, 0, sizeof(Fts5SegWriter));
  pWriter->iSegid = iSegid;

  fts5WriteDlidxGrow(p, pWriter, 1);
  pWriter->writer.pgno = 1;
  pWriter->bFirstTermInPage = 1;
  pWriter->iBtPage = 1;





  if( p->pIdxWriter==0 ){
    Fts5Config *pConfig = p->pConfig;
    fts5IndexPrepareStmt(p, &p->pIdxWriter, sqlite3_mprintf(
          "INSERT INTO '%q'.'%q_idx'(segid,term,pgno) VALUES(?,?,?)", 
          pConfig->zDb, pConfig->zName
    ));
  }

  if( p->rc==SQLITE_OK ){







    sqlite3_bind_int(p->pIdxWriter, 1, pWriter->iSegid);
  }
}

/*
** Iterator pIter was used to iterate through the input segments of on an
** incremental merge operation. This function is called if the incremental
................................................................................
      pSeg->pSeg->pgnoLast = 0;
      pSeg->pSeg->pgnoFirst = 0;
    }else{
      int iOff = pSeg->iTermLeafOffset;     /* Offset on new first leaf page */
      i64 iLeafRowid;
      Fts5Data *pData;
      int iId = pSeg->pSeg->iSegid;
      u8 aHdr[4] = {0x00, 0x00, 0x00, 0x04};

      iLeafRowid = FTS5_SEGMENT_ROWID(iId, 0, pSeg->iTermLeafPgno);
      pData = fts5DataRead(p, iLeafRowid);
      if( pData ){
        fts5BufferZero(&buf);

        fts5BufferAppendBlob(&p->rc, &buf, sizeof(aHdr), aHdr);
        fts5BufferAppendVarint(&p->rc, &buf, pSeg->term.n);
        fts5BufferAppendBlob(&p->rc, &buf, pSeg->term.n, pSeg->term.p);













        fts5BufferAppendBlob(&p->rc, &buf, pData->n - iOff, &pData->p[iOff]);




        fts5DataRelease(pData);
        pSeg->pSeg->pgnoFirst = pSeg->iTermLeafPgno;
        fts5DataDelete(p, FTS5_SEGMENT_ROWID(iId, 0, 1), iLeafRowid);
        fts5DataWrite(p, iLeafRowid, buf.p, buf.n);
      }
    }
  }
  fts5BufferFree(&buf);
}

................................................................................
    pTerm = fts5MultiIterTerm(pIter, &nTerm);
    if( nTerm!=term.n || memcmp(pTerm, term.p, nTerm) ){
      if( pnRem && writer.nLeafWritten>nRem ){
        break;
      }

      /* This is a new term. Append a term to the output segment. */

      if( bRequireDoclistTerm ){
        fts5WriteAppendZerobyte(p, &writer);
      }
      fts5WriteAppendTerm(p, &writer, nTerm, pTerm);
      fts5BufferSet(&p->rc, &term, nTerm, pTerm);
      bRequireDoclistTerm = 1;
    }

    /* Append the rowid to the output */
................................................................................

    /* Append the position-list data to the output */
    fts5ChunkIterate(p, pSegIter, (void*)&writer, fts5MergeChunkCallback);
  }

  /* Flush the last leaf page to disk. Set the output segment b-tree height
  ** and last leaf page number at the same time.  */
  fts5WriteFinish(p, &writer, &pSeg->nHeight, &pSeg->pgnoLast);

  if( fts5MultiIterEof(p, pIter) ){
    int i;

    /* Remove the redundant segments from the %_data table */
    for(i=0; i<nInput; i++){
      fts5DataRemoveSegment(p, pLvl->aSeg[i].iSegid);
................................................................................
  const int nCrisis = p->pConfig->nCrisisMerge;
  Fts5Structure *pStruct = *ppStruct;
  int iLvl = 0;

  assert( p->rc!=SQLITE_OK || pStruct->nLevel>0 );
  while( p->rc==SQLITE_OK && pStruct->aLevel[iLvl].nSeg>=nCrisis ){
    fts5IndexMergeLevel(p, &pStruct, iLvl, 0);

    fts5StructurePromote(p, iLvl+1, pStruct);
    iLvl++;
  }
  *ppStruct = pStruct;
}

static int fts5IndexReturn(Fts5Index *p){
................................................................................
** in a 32-bit integer. Return the size of the largest prefix of this 
** list nMax bytes or less in size.
*/
static int fts5PoslistPrefix(const u8 *aBuf, int nMax){
  int ret;
  u32 dummy;
  ret = fts5GetVarint32(aBuf, dummy);

  while( 1 ){
    int i = fts5GetVarint32(&aBuf[ret], dummy);
    if( (ret + i) > nMax ) break;
    ret += i;

  }
  return ret;
}

#define fts5BufferSafeAppendBlob(pBuf, pBlob, nBlob) { \
  assert( pBuf->nSpace>=(pBuf->n+nBlob) );             \
  memcpy(&pBuf->p[pBuf->n], pBlob, nBlob);             \
................................................................................
  pStruct = fts5StructureRead(p);
  iSegid = fts5AllocateSegid(p, pStruct);

  if( iSegid ){
    const int pgsz = p->pConfig->pgsz;

    Fts5StructureSegment *pSeg;   /* New segment within pStruct */
    int nHeight;                  /* Height of new segment b-tree */
    Fts5Buffer *pBuf;             /* Buffer in which to assemble leaf page */

    const u8 *zPrev = 0;

    Fts5SegWriter writer;
    fts5WriteInit(p, &writer, iSegid);

    /* Pre-allocate the buffer used to assemble leaf pages to the target
    ** page size.  */
    assert( pgsz>0 );
    pBuf = &writer.writer.buf;
    fts5BufferGrow(&p->rc, pBuf, pgsz + 20);



    /* Begin scanning through hash table entries. This loop runs once for each
    ** term/doclist currently stored within the hash table. */
    if( p->rc==SQLITE_OK ){
      memset(pBuf->p, 0, 4);
      pBuf->n = 4;
      p->rc = sqlite3Fts5HashScanInit(pHash, 0, 0);
    }
    while( p->rc==SQLITE_OK && 0==sqlite3Fts5HashScanEof(pHash) ){
      const char *zTerm;          /* Buffer containing term */
      int nTerm;                  /* Size of zTerm in bytes */
      const u8 *pDoclist;         /* Pointer to doclist for this term */
      int nDoclist;               /* Size of doclist in bytes */
      int nSuffix;                /* Size of term suffix */


      sqlite3Fts5HashScanEntry(pHash, &zTerm, &pDoclist, &nDoclist);
      nTerm = strlen(zTerm);


      /* Decide if the term will fit on the current leaf. If it will not, 
      ** flush the leaf to disk here.  */
      if( pBuf->n>4 && (pBuf->n + nTerm + 2) > pgsz ){
        fts5WriteFlushLeaf(p, &writer);
        pBuf = &writer.writer.buf;
        if( (nTerm + 32) > pBuf->nSpace ){
          fts5BufferGrow(&p->rc, pBuf, nTerm + 32 - pBuf->n);
          if( p->rc ) break;
        }
      }

      /* Write the term to the leaf. And if it is the first on the leaf, and
      ** the leaf is not page number 1, push it up into the b-tree hierarchy 
      ** as well.  */
      if( writer.bFirstTermInPage==0 ){
        int nPre = fts5PrefixCompress(nTerm, zPrev, nTerm, (const u8*)zTerm);
        pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], nPre);
        nSuffix = nTerm - nPre;
      }else{
        fts5PutU16(&pBuf->p[2], pBuf->n);
        writer.bFirstTermInPage = 0;
        if( writer.writer.pgno!=1 ){
          int nPre = fts5PrefixCompress(nTerm, zPrev, nTerm, (const u8*)zTerm);
          fts5WriteBtreeTerm(p, &writer, nPre+1, (const u8*)zTerm);
          pBuf = &writer.writer.buf;
          assert( nPre<nTerm );
        }
        nSuffix = nTerm;
      }
      pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], nSuffix);
      fts5BufferSafeAppendBlob(pBuf, (const u8*)&zTerm[nTerm-nSuffix], nSuffix);

      /* We just wrote a term into page writer.aWriter[0].pgno. If a 
      ** doclist-index is to be generated for this doclist, it will be
      ** associated with this page. */
      assert( writer.nDlidx>0 && writer.aDlidx[0].buf.n==0 );
      writer.aDlidx[0].pgno = writer.writer.pgno;

      if( pgsz>=(pBuf->n + nDoclist + 1) ){

        /* The entire doclist will fit on the current leaf. */
        fts5BufferSafeAppendBlob(pBuf, pDoclist, nDoclist);
      }else{
        i64 iRowid = 0;
        i64 iDelta = 0;
        int iOff = 0;

        writer.bFirstRowidInPage = 0;

        /* The entire doclist will not fit on this leaf. The following 
        ** loop iterates through the poslists that make up the current 
        ** doclist.  */
        while( p->rc==SQLITE_OK && iOff<nDoclist ){
          int nPos;
          int nCopy;
................................................................................
            writer.bFirstRowidInPage = 0;
            fts5WriteDlidxAppend(p, &writer, iRowid);
          }else{
            pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iDelta);
          }
          assert( pBuf->n<=pBuf->nSpace );

          if( (pBuf->n + nCopy) <= pgsz ){
            /* The entire poslist will fit on the current leaf. So copy
            ** it in one go. */
            fts5BufferSafeAppendBlob(pBuf, &pDoclist[iOff], nCopy);
          }else{
            /* The entire poslist will not fit on this leaf. So it needs
            ** to be broken into sections. The only qualification being
            ** that each varint must be stored contiguously.  */
            const u8 *pPoslist = &pDoclist[iOff];
            int iPos = 0;
            while( p->rc==SQLITE_OK ){
              int nSpace = pgsz - pBuf->n;
              int n = 0;
              if( (nCopy - iPos)<=nSpace ){
                n = nCopy - iPos;
              }else{
                n = fts5PoslistPrefix(&pPoslist[iPos], nSpace);
              }
              assert( n>0 );
              fts5BufferSafeAppendBlob(pBuf, &pPoslist[iPos], n);
              iPos += n;
              if( pBuf->n>=pgsz ){
                fts5WriteFlushLeaf(p, &writer);
                pBuf = &writer.writer.buf;
              }
              if( iPos>=nCopy ) break;
            }
          }
          iOff += nCopy;
        }
      }


      pBuf->p[pBuf->n++] = '\0';
      assert( pBuf->n<=pBuf->nSpace );
      zPrev = (const u8*)zTerm;
      sqlite3Fts5HashScanNext(pHash);
    }
    sqlite3Fts5HashClear(pHash);
    fts5WriteFinish(p, &writer, &nHeight, &pgnoLast);

    /* Update the Fts5Structure. It is written back to the database by the
    ** fts5StructureRelease() call below.  */
    if( pStruct->nLevel==0 ){
      fts5StructureAddLevel(&p->rc, &pStruct);
    }
    fts5StructureExtendLevel(&p->rc, pStruct, 0, 1, 0);
    if( p->rc==SQLITE_OK ){
      pSeg = &pStruct->aLevel[0].aSeg[ pStruct->aLevel[0].nSeg++ ];
      pSeg->iSegid = iSegid;
      pSeg->nHeight = nHeight;
      pSeg->pgnoFirst = 1;
      pSeg->pgnoLast = pgnoLast;
      pStruct->nSegment++;
    }
    fts5StructurePromote(p, 0, pStruct);
  }

................................................................................
}

static void fts5PoslistCallback(
  Fts5Index *p, 
  void *pCtx, 
  const u8 *pChunk, int nChunk
){


  fts5BufferAppendBlob(&p->rc, (Fts5Buffer*)pCtx, nChunk, pChunk);

}

/*
** Iterator pIter currently points to a valid entry (not EOF). This
** function appends the position list data for the current entry to
** buffer pBuf. It does not make a copy of the position-list size
** field.
................................................................................
      fts5BufferFree(&aBuf[i]);
    }
    fts5MultiIterFree(p, p1);

    pData = fts5IdxMalloc(p, sizeof(Fts5Data) + doclist.n);
    if( pData ){
      pData->p = (u8*)&pData[1];
      pData->n = doclist.n;
      memcpy(pData->p, doclist.p, doclist.n);
      fts5MultiIterNew2(p, pData, bDesc, ppIter);
    }
    fts5BufferFree(&doclist);
  }

  fts5StructureRelease(pStruct);
................................................................................
       || (flags & FTS5INDEX_QUERY_SCAN)==FTS5INDEX_QUERY_SCAN
  );

  if( sqlite3Fts5BufferGrow(&p->rc, &buf, nToken+1)==0 ){
    memcpy(&buf.p[1], pToken, nToken);

#ifdef SQLITE_DEBUG





    if( flags & FTS5INDEX_QUERY_TEST_NOIDX ){
      assert( flags & FTS5INDEX_QUERY_PREFIX );
      iIdx = 1+pConfig->nPrefix;
    }else
#endif
    if( flags & FTS5INDEX_QUERY_PREFIX ){
      int nChar = fts5IndexCharlen(pToken, nToken);
      for(iIdx=1; iIdx<=pConfig->nPrefix; iIdx++){
................................................................................
  int *pn,                        /* OUT: Size of position-list in bytes */
  i64 *piRowid                    /* OUT: Current rowid */
){
  Fts5SegIter *pSeg = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
  assert( pIter->pIndex->rc==SQLITE_OK );
  *piRowid = pSeg->iRowid;
  *pn = pSeg->nPos;
  if( pSeg->iLeafOffset+pSeg->nPos <= pSeg->pLeaf->n ){
    *pp = &pSeg->pLeaf->p[pSeg->iLeafOffset];
  }else{
    fts5BufferZero(&pIter->poslist);
    fts5SegiterPoslist(pIter->pIndex, pSeg, &pIter->poslist);
    *pp = pIter->poslist.p;
  }
  return fts5IndexReturn(pIter->pIndex);
................................................................................
int sqlite3Fts5IndexGetAverages(Fts5Index *p, i64 *pnRow, i64 *anSize){
  int nCol = p->pConfig->nCol;
  Fts5Data *pData;

  *pnRow = 0;
  memset(anSize, 0, sizeof(i64) * nCol);
  pData = fts5DataRead(p, FTS5_AVERAGES_ROWID);
  if( p->rc==SQLITE_OK && pData->n ){
    int i = 0;
    int iCol;
    i += fts5GetVarint(&pData->p[i], (u64*)pnRow);
    for(iCol=0; i<pData->n && iCol<nCol; iCol++){
      i += fts5GetVarint(&pData->p[i], (u64*)&anSize[iCol]);
    }
  }

  fts5DataRelease(pData);
  return fts5IndexReturn(p);
}
................................................................................
    if( rc==SQLITE_OK ){
      int f = flags|FTS5INDEX_QUERY_DESC;
      rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
    }
    if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;

    /* If this is a prefix query, check that the results returned if the
    ** the index is disabled are the same. In both ASC and DESC order. */






    if( iIdx>0 && rc==SQLITE_OK ){
      int f = flags|FTS5INDEX_QUERY_TEST_NOIDX;
      ck2 = 0;
      rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
      if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
    }
    if( iIdx>0 && rc==SQLITE_OK ){
      int f = flags|FTS5INDEX_QUERY_TEST_NOIDX|FTS5INDEX_QUERY_DESC;
      ck2 = 0;
      rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
      if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;

    }

    cksum3 ^= ck1;
    fts5BufferSet(&rc, pPrev, n, (const u8*)z);

    if( rc==SQLITE_OK && cksum3!=expected ){
      rc = FTS5_CORRUPT;
................................................................................
  int iLast
){
  int i;

  /* Now check that the iter.nEmpty leaves following the current leaf
  ** (a) exist and (b) contain no terms. */
  for(i=iFirst; p->rc==SQLITE_OK && i<=iLast; i++){
    Fts5Data *pLeaf = fts5DataRead(p, FTS5_SEGMENT_ROWID(pSeg->iSegid, 0, i));
    if( pLeaf ){
      if( 0!=fts5GetU16(&pLeaf->p[2]) ) p->rc = FTS5_CORRUPT;
      if( i>=iNoRowid && 0!=fts5GetU16(&pLeaf->p[0]) ) p->rc = FTS5_CORRUPT;
    }
    fts5DataRelease(pLeaf);
    if( p->rc ) break;
  }
}




















































static void fts5IndexIntegrityCheckSegment(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5StructureSegment *pSeg      /* Segment to check internal consistency */
){
  Fts5Config *pConfig = p->pConfig;
  sqlite3_stmt *pStmt = 0;
................................................................................
      pConfig->zDb, pConfig->zName, pSeg->iSegid
  ));

  /* Iterate through the b-tree hierarchy.  */
  while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
    i64 iRow;                     /* Rowid for this leaf */
    Fts5Data *pLeaf;              /* Data for this leaf */
    int iOff;                     /* Offset of first term on leaf */

    int nIdxTerm = sqlite3_column_bytes(pStmt, 1);
    const char *zIdxTerm = (const char*)sqlite3_column_text(pStmt, 1);
    int iIdxLeaf = sqlite3_column_int(pStmt, 2);
    int bIdxDlidx = sqlite3_column_int(pStmt, 3);

    /* If the leaf in question has already been trimmed from the segment, 
    ** ignore this b-tree entry. Otherwise, load it into memory. */
    if( iIdxLeaf<pSeg->pgnoFirst ) continue;
    iRow = FTS5_SEGMENT_ROWID(pSeg->iSegid, 0, iIdxLeaf);
    pLeaf = fts5DataRead(p, iRow);
    if( pLeaf==0 ) break;

    /* Check that the leaf contains at least one term, and that it is equal
    ** to or larger than the split-key in zIdxTerm.  Also check that if there
    ** is also a rowid pointer within the leaf page header, it points to a
    ** location before the term.  */
    iOff = fts5GetU16(&pLeaf->p[2]);
    if( iOff==0 ){
      p->rc = FTS5_CORRUPT;
    }else{

      int iRowidOff;
      int nTerm;                  /* Size of term on leaf in bytes */
      int res;                    /* Comparison of term and split-key */


      iRowidOff = fts5GetU16(&pLeaf->p[0]);
      if( iRowidOff>=iOff ){
        p->rc = FTS5_CORRUPT;
      }else{
        iOff += fts5GetVarint32(&pLeaf->p[iOff], nTerm);
        res = memcmp(&pLeaf->p[iOff], zIdxTerm, MIN(nTerm, nIdxTerm));
        if( res==0 ) res = nTerm - nIdxTerm;
        if( res<0 ) p->rc = FTS5_CORRUPT;
      }


    }
    fts5DataRelease(pLeaf);
    if( p->rc ) break;


    /* Now check that the iter.nEmpty leaves following the current leaf
    ** (a) exist and (b) contain no terms. */
................................................................................
      for(pDlidx=fts5DlidxIterInit(p, 0, iSegid, iIdxLeaf);
          fts5DlidxIterEof(p, pDlidx)==0;
          fts5DlidxIterNext(p, pDlidx)
      ){

        /* Check any rowid-less pages that occur before the current leaf. */
        for(iPg=iPrevLeaf+1; iPg<fts5DlidxIterPgno(pDlidx); iPg++){
          iKey = FTS5_SEGMENT_ROWID(iSegid, 0, iPg);
          pLeaf = fts5DataRead(p, iKey);
          if( pLeaf ){
            if( fts5GetU16(&pLeaf->p[0])!=0 ) p->rc = FTS5_CORRUPT;
            fts5DataRelease(pLeaf);
          }
        }
        iPrevLeaf = fts5DlidxIterPgno(pDlidx);

        /* Check that the leaf page indicated by the iterator really does
        ** contain the rowid suggested by the same. */
        iKey = FTS5_SEGMENT_ROWID(iSegid, 0, iPrevLeaf);
        pLeaf = fts5DataRead(p, iKey);
        if( pLeaf ){
          i64 iRowid;
          int iRowidOff = fts5GetU16(&pLeaf->p[0]);

          if( iRowidOff>=pLeaf->n ){
            p->rc = FTS5_CORRUPT;
          }else{
            fts5GetVarint(&pLeaf->p[iRowidOff], (u64*)&iRowid);
            if( iRowid!=fts5DlidxIterRowid(pDlidx) ) p->rc = FTS5_CORRUPT;
          }
          fts5DataRelease(pLeaf);
        }
................................................................................
  for(iLvl=0; iLvl<p->nLevel; iLvl++){
    Fts5StructureLevel *pLvl = &p->aLevel[iLvl];
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, 
        " {lvl=%d nMerge=%d nSeg=%d", iLvl, pLvl->nMerge, pLvl->nSeg
    );
    for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
      Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, 
          " {id=%d h=%d leaves=%d..%d}", pSeg->iSegid, pSeg->nHeight, 
          pSeg->pgnoFirst, pSeg->pgnoLast
      );
    }
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "}");
  }
}

/*
................................................................................
**
** The return value is the number of bytes read from the input buffer.
*/
static int fts5DecodeDoclist(int *pRc, Fts5Buffer *pBuf, const u8 *a, int n){
  i64 iDocid;
  int iOff = 0;


  iOff = sqlite3Fts5GetVarint(&a[iOff], (u64*)&iDocid);
  sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " rowid=%lld", iDocid);

  while( iOff<n ){
    int nPos;
    int bDummy;
    iOff += fts5GetPoslistSize(&a[iOff], &nPos, &bDummy);
    iOff += fts5DecodePoslist(pRc, pBuf, &a[iOff], MIN(n-iOff, nPos));
    if( iOff<n ){
      i64 iDelta;
      iOff += sqlite3Fts5GetVarint(&a[iOff], (u64*)&iDelta);
      if( iDelta==0 ) return iOff;
      iDocid += iDelta;
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " rowid=%lld", iDocid);
    }
  }

  return iOff;
}

/*
................................................................................
  Fts5Buffer s;                   /* Build up text to return here */
  int rc = SQLITE_OK;             /* Return code */
  int nSpace = 0;

  assert( nArg==2 );
  memset(&s, 0, sizeof(Fts5Buffer));
  iRowid = sqlite3_value_int64(apVal[0]);




  n = sqlite3_value_bytes(apVal[1]);
  aBlob = sqlite3_value_blob(apVal[1]);

  nSpace = n + FTS5_DATA_ZERO_PADDING;
  a = (u8*)sqlite3Fts5MallocZero(&rc, nSpace);
  if( a==0 ) goto decode_out;
  memcpy(a, aBlob, n);


  fts5DecodeRowid(iRowid, &iSegid, &bDlidx, &iHeight, &iPgno);

  fts5DebugRowid(&rc, &s, iRowid);
  if( bDlidx ){
    Fts5Data dlidx;
    Fts5DlidxLvl lvl;

    dlidx.p = a;
    dlidx.n = n;

    memset(&lvl, 0, sizeof(Fts5DlidxLvl));
    lvl.pData = &dlidx;
    lvl.iLeafPgno = iPgno;

    for(fts5DlidxLvlNext(&lvl); lvl.bEof==0; fts5DlidxLvlNext(&lvl)){
      sqlite3Fts5BufferAppendPrintf(&rc, &s, 
................................................................................
  }else if( iSegid==0 ){
    if( iRowid==FTS5_AVERAGES_ROWID ){
      /* todo */
    }else{
      fts5DecodeStructure(&rc, &s, a, n);
    }
  }else{
    Fts5Buffer term;



    int iTermOff = 0;
    int iRowidOff = 0;
    int iOff;
    int nKeep = 0;

    memset(&term, 0, sizeof(Fts5Buffer));

    if( n>=4 ){
      iRowidOff = fts5GetU16(&a[0]);
      iTermOff = fts5GetU16(&a[2]);
    }else{
      sqlite3Fts5BufferSet(&rc, &s, 8, (const u8*)"corrupt");
      goto decode_out;





    }



    if( iRowidOff ){
      iOff = iRowidOff;
    }else if( iTermOff ){
      iOff = iTermOff;
    }else{
      iOff = n;
    }
    fts5DecodePoslist(&rc, &s, &a[4], iOff-4);

    assert( iRowidOff==0 || iOff==iRowidOff );
    if( iRowidOff ){



      iOff += fts5DecodeDoclist(&rc, &s, &a[iOff], n-iOff);
    }





    assert( iTermOff==0 || iOff==iTermOff );




    while( iOff<n ){

      int nByte;





      iOff += fts5GetVarint32(&a[iOff], nByte);
      term.n= nKeep;


      fts5BufferAppendBlob(&rc, &term, nByte, &a[iOff]);
      iOff += nByte;

      sqlite3Fts5BufferAppendPrintf(
          &rc, &s, " term=%.*s", term.n, (const char*)term.p
          );
      iOff += fts5DecodeDoclist(&rc, &s, &a[iOff], n-iOff);
      if( iOff<n ){
        iOff += fts5GetVarint32(&a[iOff], nKeep);
      }
    }
    fts5BufferFree(&term);
  }
  
 decode_out:
  sqlite3_free(a);
  if( rc==SQLITE_OK ){
    sqlite3_result_text(pCtx, (const char*)s.p, s.n, SQLITE_TRANSIENT);
................................................................................
  if( nArg==0 ){
    sqlite3_result_error(pCtx, "should be: fts5_rowid(subject, ....)", -1);
  }else{
    zArg = (const char*)sqlite3_value_text(apVal[0]);
    if( 0==sqlite3_stricmp(zArg, "segment") ){
      i64 iRowid;
      int segid, height, pgno;
      if( nArg!=4 ){
        sqlite3_result_error(pCtx, 
            "should be: fts5_rowid('segment', segid, height, pgno))", -1
        );
      }else{
        segid = sqlite3_value_int(apVal[1]);
        height = sqlite3_value_int(apVal[2]);
        pgno = sqlite3_value_int(apVal[3]);
        iRowid = FTS5_SEGMENT_ROWID(segid, height, pgno);
        sqlite3_result_int64(pCtx, iRowid);
      }
    }else {
      sqlite3_result_error(pCtx, 
        "first arg to fts5_rowid() must be 'segment' "
        "or 'start-of-index'"
        , -1
      );
    }
  }
}

/*
** This is called as part of registering the FTS5 module with database







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....
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4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
....
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
....
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
....
4955
4956
4957
4958
4959
4960
4961

4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979

4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
....
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
....
5237
5238
5239
5240
5241
5242
5243
5244

5245
5246
5247
5248
5249
5250
5251
5252
....
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
....
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351

5352
5353
5354
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5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
....
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395



5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
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5414
5415


5416
5417
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5419
5420
5421
5422
5423
5424
5425

5426
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5433
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5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448


5449
5450
5451
5452
5453
5454
5455
5456
5457
....
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485

5486
5487
5488
5489
5490
5491
5492


5493
5494
5495
5496
5497
5498
5499
**
**   Then, for each level from 0 to nMax:
**
**     + number of input segments in ongoing merge.
**     + total number of segments in level.
**     + for each segment from oldest to newest:
**         + segment id (always > 0)

**         + first leaf page number (often 1, always greater than 0)
**         + final leaf page number
**
** 2. The Averages Record:
**
**   A single record within the %_data table. The data is a list of varints.
**   The first value is the number of rows in the index. Then, for each column
**   from left to right, the total number of tokens in the column for all
**   rows of the table.
**
** 3. Segment leaves:
**
**   TERM/DOCLIST FORMAT:
**
**     Most of each segment leaf is taken up by term/doclist data. The 
**     general format of term/doclist, starting with the first term
**     on the leaf page, is:
**
**         varint : size of first term
**         blob:    first term data
**         doclist: first doclist
**         zero-or-more {
**           varint:  number of bytes in common with previous term
**           varint:  number of bytes of new term data (nNew)
................................................................................
**
**         varint:  first rowid
**         poslist: first poslist
**         zero-or-more {
**           varint:  rowid delta (always > 0)
**           poslist: next poslist
**         }

**
**     poslist format:
**
**         varint: size of poslist in bytes multiplied by 2, not including
**                 this field. Plus 1 if this entry carries the "delete" flag.
**         collist: collist for column 0
**         zero-or-more {
................................................................................
**     collist format:
**
**         varint: first offset + 2
**         zero-or-more {
**           varint: offset delta + 2
**         }
**
**   PAGE FORMAT
**
**     Each leaf page begins with a 4-byte header containing 2 16-bit 
**     unsigned integer fields in big-endian format. They are:
**
**       * The byte offset of the first rowid on the page, if it exists
**         and occurs before the first term (otherwise 0).
**
**       * The byte offset of the start of the page footer. If the page
**         footer is 0 bytes in size, then this field is the same as the
**         size of the leaf page in bytes.
**
**     The page footer consists of a single varint for each term located
**     on the page. Each varint is the byte offset of the current term
**     within the page, delta-compressed against the previous value. In
**     other words, the first varint in the footer is the byte offset of
**     the first term, the second is the byte offset of the second less that
**     of the first, and so on.
**
**     The term/doclist format described above is accurate if the entire
**     term/doclist data fits on a single leaf page. If this is not the case,
**     the format is changed in two ways:
**
**       + if the first rowid on a page occurs before the first term, it
**         is stored as a literal value:
**
**             varint:  first rowid
**
**       + the first term on each page is stored in the same way as the
**         very first term of the segment:
**
**             varint : size of first term
**             blob:    first term data
**







































** 5. Segment doclist indexes:
**
**   Doclist indexes are themselves b-trees, however they usually consist of
**   a single leaf record only. The format of each doclist index leaf page 
**   is:
**
**     * Flags byte. Bits are:
................................................................................
/*
** Rowids for the averages and structure records in the %_data table.
*/
#define FTS5_AVERAGES_ROWID     1    /* Rowid used for the averages record */
#define FTS5_STRUCTURE_ROWID   10    /* The structure record */

/*
** Macros determining the rowids used by segment leaves and dlidx leaves

** and nodes. All nodes and leaves are stored in the %_data table with large
** positive rowids.
**
** Each segment has a unique non-zero 16-bit id.

**
** The rowid for each segment leaf is found by passing the segment id and 
** the leaf page number to the FTS5_SEGMENT_ROWID macro. Leaves are numbered
** sequentially starting from 1.









*/
#define FTS5_DATA_ID_B     16     /* Max seg id number 65535 */
#define FTS5_DATA_DLI_B     1     /* Doclist-index flag (1 bit) */
#define FTS5_DATA_HEIGHT_B  5     /* Max dlidx tree height of 32 */
#define FTS5_DATA_PAGE_B   31     /* Max page number of 2147483648 */

#define fts5_dri(segid, dlidx, height, pgno) (                                 \
 ((i64)(segid)  << (FTS5_DATA_PAGE_B+FTS5_DATA_HEIGHT_B+FTS5_DATA_DLI_B)) +    \
 ((i64)(dlidx)  << (FTS5_DATA_PAGE_B + FTS5_DATA_HEIGHT_B)) +                  \
 ((i64)(height) << (FTS5_DATA_PAGE_B)) +                                       \
 ((i64)(pgno))                                                                 \
)

#define FTS5_SEGMENT_ROWID(segid, pgno)       fts5_dri(segid, 0, 0, pgno)
#define FTS5_DLIDX_ROWID(segid, height, pgno) fts5_dri(segid, 1, height, pgno)

/*
** Maximum segments permitted in a single index 
*/
#define FTS5_MAX_SEGMENT 2000

#ifdef SQLITE_DEBUG
................................................................................
typedef struct Fts5SegWriter Fts5SegWriter;
typedef struct Fts5Structure Fts5Structure;
typedef struct Fts5StructureLevel Fts5StructureLevel;
typedef struct Fts5StructureSegment Fts5StructureSegment;

struct Fts5Data {
  u8 *p;                          /* Pointer to buffer containing record */
  int nn;                         /* Size of record in bytes */
  int szLeaf;                     /* Size of leaf without page-index */
};

/*
** One object per %_data table.
*/
struct Fts5Index {
  Fts5Config *pConfig;            /* Virtual table configuration */
................................................................................
/*
** The contents of the "structure" record for each index are represented
** using an Fts5Structure record in memory. Which uses instances of the 
** other Fts5StructureXXX types as components.
*/
struct Fts5StructureSegment {
  int iSegid;                     /* Segment id */

  int pgnoFirst;                  /* First leaf page number in segment */
  int pgnoLast;                   /* Last leaf page number in segment */
};
struct Fts5StructureLevel {
  int nMerge;                     /* Number of segments in incr-merge */
  int nSeg;                       /* Total number of segments on level */
  Fts5StructureSegment *aSeg;     /* Array of segments. aSeg[0] is oldest. */
................................................................................
};

/*
** An object of type Fts5SegWriter is used to write to segments.
*/
struct Fts5PageWriter {
  int pgno;                       /* Page number for this page */
  int iPrevPgidx;                 /* Previous value written into pgidx */
  Fts5Buffer buf;                 /* Buffer containing leaf data */
  Fts5Buffer pgidx;               /* Buffer containing page-index */
  Fts5Buffer term;                /* Buffer containing previous term on page */
};
struct Fts5DlidxWriter {
  int pgno;                       /* Page number for this page */
  int bPrevValid;                 /* True if iPrev is valid */
  i64 iPrev;                      /* Previous rowid value written to page */
  Fts5Buffer buf;                 /* Buffer containing page data */
................................................................................
};
struct Fts5SegWriter {
  int iSegid;                     /* Segid to write to */
  Fts5PageWriter writer;          /* PageWriter object */
  i64 iPrevRowid;                 /* Previous rowid written to current leaf */
  u8 bFirstRowidInDoclist;        /* True if next rowid is first in doclist */
  u8 bFirstRowidInPage;           /* True if next rowid is first in page */
  /* TODO1: Can use (writer.pgidx.n==0) instead of bFirstTermInPage */
  u8 bFirstTermInPage;            /* True if next term will be first in leaf */
  int nLeafWritten;               /* Number of leaf pages written */
  int nEmpty;                     /* Number of contiguous term-less nodes */

  int nDlidx;                     /* Allocated size of aDlidx[] array */
  Fts5DlidxWriter *aDlidx;        /* Array of Fts5DlidxWriter objects */

................................................................................
**
** iRowidOffset/nRowidOffset/aRowidOffset:
**     These are used if the FTS5_SEGITER_REVERSE flag is set.
**
**     For each rowid on the page corresponding to the current term, the
**     corresponding aRowidOffset[] entry is set to the byte offset of the
**     start of the "position-list-size" field within the page.
**
** iTermIdx:
**     Index of current term on iTermLeafPgno.
*/
struct Fts5SegIter {
  Fts5StructureSegment *pSeg;     /* Segment to iterate through */
  int flags;                      /* Mask of configuration flags */
  int iLeafPgno;                  /* Current leaf page number */
  Fts5Data *pLeaf;                /* Current leaf data */
  Fts5Data *pNextLeaf;            /* Leaf page (iLeafPgno+1) */
  int iLeafOffset;                /* Byte offset within current leaf */

  /* The page and offset from which the current term was read. The offset 
  ** is the offset of the first rowid in the current doclist.  */
  int iTermLeafPgno;
  int iTermLeafOffset;

  int iPgidxOff;                  /* Next offset in pgidx */
  int iEndofDoclist;

  /* The following are only used if the FTS5_SEGITER_REVERSE flag is set. */
  int iRowidOffset;               /* Current entry in aRowidOffset[] */
  int nRowidOffset;               /* Allocated size of aRowidOffset[] array */
  int *aRowidOffset;              /* Array of offset to rowid fields */

  Fts5DlidxIter *pDlidx;          /* If there is a doclist-index */
................................................................................

  /* Variables populated based on current entry. */
  Fts5Buffer term;                /* Current term */
  i64 iRowid;                     /* Current rowid */
  int nPos;                       /* Number of bytes in current position list */
  int bDel;                       /* True if the delete flag is set */
};

/*
** Argument is a pointer to an Fts5Data structure that contains a 
** leaf page.
*/
#define ASSERT_SZLEAF_OK(x) assert( \
    (x)->szLeaf==(x)->nn || (x)->szLeaf==fts5GetU16(&(x)->p[2]) \
)

#define FTS5_SEGITER_ONETERM 0x01
#define FTS5_SEGITER_REVERSE 0x02


/* 
** Argument is a pointer to an Fts5Data structure that contains a leaf
** page. This macro evaluates to true if the leaf contains no terms, or
** false if it contains at least one term.
*/
#define fts5LeafIsTermless(x) ((x)->szLeaf >= (x)->nn)

#define fts5LeafTermOff(x, i) (fts5GetU16(&(x)->p[(x)->szLeaf + (i)*2]))

#define fts5LeafFirstRowidOff(x) (fts5GetU16((x)->p))

/*
** poslist:
**   Used by sqlite3Fts5IterPoslist() when the poslist needs to be buffered.
**   There is no way to tell if this is populated or not.
*/
struct Fts5IndexIter {
  Fts5Index *pIndex;              /* Index that owns this iterator */
................................................................................
){
  int nCmp = MIN(nLeft, nRight);
  int res = memcmp(pLeft, pRight, nCmp);
  return (res==0 ? (nLeft - nRight) : res);
}
#endif

static int fts5LeafFirstTermOff(Fts5Data *pLeaf){
  int ret;
  fts5GetVarint32(&pLeaf->p[pLeaf->szLeaf], ret);
  return ret;
}

/*
** Close the read-only blob handle, if it is open.
*/
static void fts5CloseReader(Fts5Index *p){
  if( p->pReader ){
    sqlite3_blob *pReader = p->pReader;
................................................................................

    if( rc==SQLITE_OK ){
      u8 *aOut = 0;               /* Read blob data into this buffer */
      int nByte = sqlite3_blob_bytes(p->pReader);
      int nAlloc = sizeof(Fts5Data) + nByte + FTS5_DATA_PADDING;
      pRet = (Fts5Data*)sqlite3_malloc(nAlloc);
      if( pRet ){
        pRet->nn = nByte;
        aOut = pRet->p = (u8*)&pRet[1];
      }else{
        rc = SQLITE_NOMEM;
      }

      if( rc==SQLITE_OK ){
        rc = sqlite3_blob_read(p->pReader, aOut, nByte, 0);
      }
      if( rc!=SQLITE_OK ){
        sqlite3_free(pRet);
        pRet = 0;
      }else{
        /* TODO1: Fix this */
        pRet->szLeaf = fts5GetU16(&pRet->p[2]);
      }
    }
    p->rc = rc;
    p->nRead++;
  }

  assert( (pRet==0)==(p->rc!=SQLITE_OK) );
................................................................................
  p->rc = sqlite3_reset(p->pDeleter);
}

/*
** Remove all records associated with segment iSegid.
*/
static void fts5DataRemoveSegment(Fts5Index *p, int iSegid){
  i64 iFirst = FTS5_SEGMENT_ROWID(iSegid, 0);
  i64 iLast = FTS5_SEGMENT_ROWID(iSegid+1, 0)-1;
  fts5DataDelete(p, iFirst, iLast);
  if( p->pIdxDeleter==0 ){
    Fts5Config *pConfig = p->pConfig;
    fts5IndexPrepareStmt(p, &p->pIdxDeleter, sqlite3_mprintf(
          "DELETE FROM '%q'.'%q_idx' WHERE segid=?",
          pConfig->zDb, pConfig->zName
    ));
................................................................................
          nTotal * sizeof(Fts5StructureSegment)
      );

      if( rc==SQLITE_OK ){
        pLvl->nSeg = nTotal;
        for(iSeg=0; iSeg<nTotal; iSeg++){
          i += fts5GetVarint32(&pData[i], pLvl->aSeg[iSeg].iSegid);

          i += fts5GetVarint32(&pData[i], pLvl->aSeg[iSeg].pgnoFirst);
          i += fts5GetVarint32(&pData[i], pLvl->aSeg[iSeg].pgnoLast);
        }
      }else{
        fts5StructureRelease(pRet);
        pRet = 0;
      }
................................................................................
  Fts5Structure *pRet = 0;        /* Object to return */
  int iCookie;                    /* Configuration cookie */
  Fts5Data *pData;
  Fts5Buffer buf = {0, 0, 0};

  pData = fts5DataRead(p, FTS5_STRUCTURE_ROWID);
  if( p->rc ) return 0;
  /* TODO: Do we need this if the leaf-index is appended? Probably... */
  memset(&pData->p[pData->nn], 0, FTS5_DATA_PADDING);
  p->rc = fts5StructureDecode(pData->p, pData->nn, &iCookie, &pRet);
  if( p->rc==SQLITE_OK && pConfig->iCookie!=iCookie ){
    p->rc = sqlite3Fts5ConfigLoad(pConfig, iCookie);
  }

  fts5DataRelease(pData);
  if( p->rc!=SQLITE_OK ){
    fts5StructureRelease(pRet);
................................................................................
      Fts5StructureLevel *pLvl = &pStruct->aLevel[iLvl];
      fts5BufferAppendVarint(&p->rc, &buf, pLvl->nMerge);
      fts5BufferAppendVarint(&p->rc, &buf, pLvl->nSeg);
      assert( pLvl->nMerge<=pLvl->nSeg );

      for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
        fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].iSegid);

        fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].pgnoFirst);
        fts5BufferAppendVarint(&p->rc, &buf, pLvl->aSeg[iSeg].pgnoLast);
      }
    }

    fts5DataWrite(p, FTS5_STRUCTURE_ROWID, buf.p, buf.n);
    fts5BufferFree(&buf);
................................................................................
){
  if( p->rc==SQLITE_OK ){
    int iTst;
    int iPromote = -1;
    int szPromote = 0;            /* Promote anything this size or smaller */
    Fts5StructureSegment *pSeg;   /* Segment just written */
    int szSeg;                    /* Size of segment just written */
    int nSeg = pStruct->aLevel[iLvl].nSeg;


    if( nSeg==0 ) return;
    pSeg = &pStruct->aLevel[iLvl].aSeg[pStruct->aLevel[iLvl].nSeg-1];
    szSeg = (1 + pSeg->pgnoLast - pSeg->pgnoFirst);

    /* Check for condition (a) */
    for(iTst=iLvl-1; iTst>=0 && pStruct->aLevel[iTst].nSeg==0; iTst--);
    if( iTst>=0 ){
      int i;
................................................................................
    assert( pLvl->bEof==0 );
    pLvl->iOff = 1;
    pLvl->iOff += fts5GetVarint32(&pData->p[1], pLvl->iLeafPgno);
    pLvl->iOff += fts5GetVarint(&pData->p[pLvl->iOff], (u64*)&pLvl->iRowid);
    pLvl->iFirstOff = pLvl->iOff;
  }else{
    int iOff;
    for(iOff=pLvl->iOff; iOff<pData->nn; iOff++){
      if( pData->p[iOff] ) break; 
    }

    if( iOff<pData->nn ){
      i64 iVal;
      pLvl->iLeafPgno += (iOff - pLvl->iOff) + 1;
      iOff += fts5GetVarint(&pData->p[iOff], (u64*)&iVal);
      pLvl->iRowid += iVal;
      pLvl->iOff = iOff;
    }else{
      pLvl->bEof = 1;
................................................................................
/*
** Load the next leaf page into the segment iterator.
*/
static void fts5SegIterNextPage(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5SegIter *pIter              /* Iterator to advance to next page */
){
  Fts5Data *pLeaf;
  Fts5StructureSegment *pSeg = pIter->pSeg;
  fts5DataRelease(pIter->pLeaf);
  pIter->iLeafPgno++;
  if( pIter->pNextLeaf ){
    assert( pIter->iLeafPgno<=pSeg->pgnoLast );
    pIter->pLeaf = pIter->pNextLeaf;
    pIter->pNextLeaf = 0;
  }else if( pIter->iLeafPgno<=pSeg->pgnoLast ){
    pIter->pLeaf = fts5DataRead(p, 
        FTS5_SEGMENT_ROWID(pSeg->iSegid, pIter->iLeafPgno)
    );
  }else{
    pIter->pLeaf = 0;
  }
  pLeaf = pIter->pLeaf;

  if( pLeaf ){
    pIter->iPgidxOff = pLeaf->szLeaf;
    if( fts5LeafIsTermless(pLeaf) ){
      pIter->iEndofDoclist = pLeaf->nn+1;
    }else{
      pIter->iPgidxOff += fts5GetVarint32(&pLeaf->p[pIter->iPgidxOff],
          pIter->iEndofDoclist
      );
    }
  }
}

/*
** Argument p points to a buffer containing a varint to be interpreted as a
** position list size field. Read the varint and return the number of bytes
** read. Before returning, set *pnSz to the number of bytes in the position
................................................................................
**
** Leave Fts5SegIter.iLeafOffset pointing to the first byte of the 
** position list content (if any).
*/
static void fts5SegIterLoadNPos(Fts5Index *p, Fts5SegIter *pIter){
  if( p->rc==SQLITE_OK ){
    int iOff = pIter->iLeafOffset;  /* Offset to read at */
    ASSERT_SZLEAF_OK(pIter->pLeaf);
    if( iOff>=pIter->pLeaf->szLeaf ){
      p->rc = FTS5_CORRUPT;
    }else{
      const u8 *a = &pIter->pLeaf->p[iOff];
      pIter->iLeafOffset += fts5GetPoslistSize(a, &pIter->nPos, &pIter->bDel);
    }
  }
}

static void fts5SegIterLoadRowid(Fts5Index *p, Fts5SegIter *pIter){
  u8 *a = pIter->pLeaf->p;        /* Buffer to read data from */
  int iOff = pIter->iLeafOffset;

  ASSERT_SZLEAF_OK(pIter->pLeaf);
  if( iOff>=pIter->pLeaf->szLeaf ){
    fts5SegIterNextPage(p, pIter);
    if( pIter->pLeaf==0 ){
      if( p->rc==SQLITE_OK ) p->rc = FTS5_CORRUPT;
      return;
    }
    iOff = 4;
    a = pIter->pLeaf->p;
................................................................................
  iOff += fts5GetVarint32(&a[iOff], nNew);
  pIter->term.n = nKeep;
  fts5BufferAppendBlob(&p->rc, &pIter->term, nNew, &a[iOff]);
  iOff += nNew;
  pIter->iTermLeafOffset = iOff;
  pIter->iTermLeafPgno = pIter->iLeafPgno;
  pIter->iLeafOffset = iOff;

  if( pIter->iPgidxOff>=pIter->pLeaf->nn ){
    pIter->iEndofDoclist = pIter->pLeaf->nn+1;
  }else{
    int nExtra;
    pIter->iPgidxOff += fts5GetVarint32(&a[pIter->iPgidxOff], nExtra);
    pIter->iEndofDoclist += nExtra;
  }

  fts5SegIterLoadRowid(p, pIter);
}

/*
** Initialize the iterator object pIter to iterate through the entries in
** segment pSeg. The iterator is left pointing to the first entry when 
................................................................................
    memset(pIter, 0, sizeof(*pIter));
    pIter->pSeg = pSeg;
    pIter->iLeafPgno = pSeg->pgnoFirst-1;
    fts5SegIterNextPage(p, pIter);
  }

  if( p->rc==SQLITE_OK ){

    pIter->iLeafOffset = 4;
    assert_nc( pIter->pLeaf->nn>4 );
    assert( fts5LeafFirstTermOff(pIter->pLeaf)==4 );
    pIter->iPgidxOff = pIter->pLeaf->szLeaf+1;
    fts5SegIterLoadTerm(p, pIter, 0);
    fts5SegIterLoadNPos(p, pIter);
  }
}

/*
** This function is only ever called on iterators created by calls to
................................................................................
** This function advances the iterator so that it points to the last 
** relevant rowid on the page and, if necessary, initializes the 
** aRowidOffset[] and iRowidOffset variables. At this point the iterator
** is in its regular state - Fts5SegIter.iLeafOffset points to the first
** byte of the position list content associated with said rowid.
*/
static void fts5SegIterReverseInitPage(Fts5Index *p, Fts5SegIter *pIter){
  int n = pIter->pLeaf->szLeaf;
  int i = pIter->iLeafOffset;
  u8 *a = pIter->pLeaf->p;
  int iRowidOffset = 0;

  if( n>pIter->iEndofDoclist ){
    n = pIter->iEndofDoclist;
  }

  ASSERT_SZLEAF_OK(pIter->pLeaf);
  while( 1 ){
    i64 iDelta = 0;
    int nPos;
    int bDummy;

    i += fts5GetPoslistSize(&a[i], &nPos, &bDummy);
    i += nPos;
    if( i>=n ) break;
    i += fts5GetVarint(&a[i], (u64*)&iDelta);

    pIter->iRowid += iDelta;

    if( iRowidOffset>=pIter->nRowidOffset ){
      int nNew = pIter->nRowidOffset + 8;
      int *aNew = (int*)sqlite3_realloc(pIter->aRowidOffset, nNew*sizeof(int));
      if( aNew==0 ){
        p->rc = SQLITE_NOMEM;
................................................................................

  fts5DataRelease(pIter->pLeaf);
  pIter->pLeaf = 0;
  while( p->rc==SQLITE_OK && pIter->iLeafPgno>pIter->iTermLeafPgno ){
    Fts5Data *pNew;
    pIter->iLeafPgno--;
    pNew = fts5DataRead(p, FTS5_SEGMENT_ROWID(
          pIter->pSeg->iSegid, pIter->iLeafPgno
    ));
    if( pNew ){
      if( pIter->iLeafPgno==pIter->iTermLeafPgno ){
        if( pIter->iTermLeafOffset<pNew->szLeaf ){
          pIter->pLeaf = pNew;
          pIter->iLeafOffset = pIter->iTermLeafOffset;
        }
      }else{
        int iRowidOff;
        iRowidOff = fts5LeafFirstRowidOff(pNew);
        if( iRowidOff ){
          pIter->pLeaf = pNew;
          pIter->iLeafOffset = iRowidOff;
        }
      }

      if( pIter->pLeaf ){
................................................................................
      }else{
        fts5DataRelease(pNew);
      }
    }
  }

  if( pIter->pLeaf ){
    pIter->iEndofDoclist = pIter->pLeaf->nn+1;
    fts5SegIterReverseInitPage(p, pIter);
  }
}

/*
** Return true if the iterator passed as the second argument currently
** points to a delete marker. A delete marker is an entry with a 0 byte
................................................................................
      Fts5Data *pLeaf = pIter->pLeaf;
      int iOff;
      int bNewTerm = 0;
      int nKeep = 0;

      /* Search for the end of the position list within the current page. */
      u8 *a = pLeaf->p;
      int n = pLeaf->szLeaf;

      ASSERT_SZLEAF_OK(pLeaf);
      iOff = pIter->iLeafOffset + pIter->nPos;

      if( iOff<n ){
        /* The next entry is on the current page. */
        assert_nc( iOff<=pIter->iEndofDoclist );
        if( iOff>=pIter->iEndofDoclist ){


          bNewTerm = 1;



          if( iOff!=fts5LeafFirstTermOff(pLeaf) ){
            iOff += fts5GetVarint32(&a[iOff], nKeep);
          }
        }else{
          u64 iDelta;
          iOff += sqlite3Fts5GetVarint(&a[iOff], &iDelta);
          pIter->iRowid += iDelta;
          assert_nc( iDelta>0 );
        }
        pIter->iLeafOffset = iOff;

      }else if( pIter->pSeg==0 ){
        const u8 *pList = 0;
        const char *zTerm = 0;
        int nList = 0;
        if( 0==(pIter->flags & FTS5_SEGITER_ONETERM) ){
          sqlite3Fts5HashScanNext(p->pHash);
          sqlite3Fts5HashScanEntry(p->pHash, &zTerm, &pList, &nList);
        }
        if( pList==0 ){
          fts5DataRelease(pIter->pLeaf);
          pIter->pLeaf = 0;
        }else{
          pIter->pLeaf->p = (u8*)pList;
          pIter->pLeaf->nn = nList;
          pIter->pLeaf->szLeaf = nList;
          pIter->iEndofDoclist = nList+1;
          sqlite3Fts5BufferSet(&p->rc, &pIter->term, strlen(zTerm), (u8*)zTerm);
          pIter->iLeafOffset = fts5GetVarint(pList, (u64*)&pIter->iRowid);
        }
      }else{
        iOff = 0;
        /* Next entry is not on the current page */
        while( iOff==0 ){
          fts5SegIterNextPage(p, pIter);
          pLeaf = pIter->pLeaf;
          if( pLeaf==0 ) break;
          ASSERT_SZLEAF_OK(pLeaf);
          if( (iOff = fts5LeafFirstRowidOff(pLeaf)) && iOff<pLeaf->szLeaf ){
            iOff += sqlite3Fts5GetVarint(&pLeaf->p[iOff], (u64*)&pIter->iRowid);
            pIter->iLeafOffset = iOff;


            if( pLeaf->nn>pLeaf->szLeaf ){
              pIter->iPgidxOff = pLeaf->szLeaf + fts5GetVarint32(
                  &pLeaf->p[pLeaf->szLeaf], pIter->iEndofDoclist
              );
            }

          }
          else if( pLeaf->nn>pLeaf->szLeaf ){
            pIter->iPgidxOff = pLeaf->szLeaf + fts5GetVarint32(
                &pLeaf->p[pLeaf->szLeaf], iOff
            );
            pIter->iLeafOffset = iOff;
            pIter->iEndofDoclist = iOff;
            bNewTerm = 1;
          }
          if( iOff>=pLeaf->szLeaf ){
            p->rc = FTS5_CORRUPT;
            return;
          }
        }
      }

      /* Check if the iterator is now at EOF. If so, return early. */
      if( pIter->pLeaf ){
        if( bNewTerm ){
          if( pIter->flags & FTS5_SEGITER_ONETERM ){
            fts5DataRelease(pIter->pLeaf);
            pIter->pLeaf = 0;
          }else{
            int nExtra;
            fts5SegIterLoadTerm(p, pIter, nKeep);
            fts5SegIterLoadNPos(p, pIter);
            if( pbNewTerm ) *pbNewTerm = 1;
          }
        }else{
          fts5SegIterLoadNPos(p, pIter);
        }
................................................................................
  Fts5DlidxIter *pDlidx = pIter->pDlidx;
  Fts5Data *pLast = 0;
  int pgnoLast = 0;

  if( pDlidx ){
    int iSegid = pIter->pSeg->iSegid;
    pgnoLast = fts5DlidxIterPgno(pDlidx);
    pLast = fts5DataRead(p, FTS5_SEGMENT_ROWID(iSegid, pgnoLast));
  }else{
    int iOff;                               /* Byte offset within pLeaf */
    Fts5Data *pLeaf = pIter->pLeaf;         /* Current leaf data */

    /* Currently, Fts5SegIter.iLeafOffset (and iOff) points to the first 
    ** byte of position-list content for the current rowid. Back it up
    ** so that it points to the start of the position-list size field. */
    pIter->iLeafOffset -= sqlite3Fts5GetVarintLen(pIter->nPos*2+pIter->bDel);





















    /* If this condition is true then the largest rowid for the current
    ** term may not be stored on the current page. So search forward to
    ** see where said rowid really is.  */
    if( pIter->iEndofDoclist>=pLeaf->szLeaf ){
      int pgno;
      Fts5StructureSegment *pSeg = pIter->pSeg;

      /* The last rowid in the doclist may not be on the current page. Search
      ** forward to find the page containing the last rowid.  */
      for(pgno=pIter->iLeafPgno+1; !p->rc && pgno<=pSeg->pgnoLast; pgno++){
        i64 iAbs = FTS5_SEGMENT_ROWID(pSeg->iSegid, pgno);
        Fts5Data *pNew = fts5DataRead(p, iAbs);
        if( pNew ){
          int iRowid, bTermless;
          iRowid = fts5LeafFirstRowidOff(pNew);
          bTermless = fts5LeafIsTermless(pNew);
          if( iRowid ){
            SWAPVAL(Fts5Data*, pNew, pLast);
            pgnoLast = pgno;
          }
          fts5DataRelease(pNew);
          if( bTermless==0 ) break;
        }
      }
    }
  }

  /* If pLast is NULL at this point, then the last rowid for this doclist
  ** lies on the page currently indicated by the iterator. In this case 
................................................................................
  ** field associated with the first relevant rowid on the page.
  **
  ** Or, if pLast is non-NULL, then it is the page that contains the last
  ** rowid. In this case configure the iterator so that it points to the
  ** first rowid on this page.
  */
  if( pLast ){

    int iOff;
    fts5DataRelease(pIter->pLeaf);
    pIter->pLeaf = pLast;
    pIter->iLeafPgno = pgnoLast;
    iOff = fts5LeafFirstRowidOff(pLast);
    iOff += fts5GetVarint(&pLast->p[iOff], (u64*)&pIter->iRowid);
    pIter->iLeafOffset = iOff;

    if( fts5LeafIsTermless(pLast) ){
      pIter->iEndofDoclist = pLast->nn+1;
    }else{
      pIter->iEndofDoclist = fts5LeafFirstTermOff(pLast);
    }

  }

  fts5SegIterReverseInitPage(p, pIter);
}

/*
** Iterator pIter currently points to the first rowid of a doclist.
................................................................................

  assert( pIter->flags & FTS5_SEGITER_ONETERM );
  assert( pIter->pDlidx==0 );

  /* Check if the current doclist ends on this page. If it does, return
  ** early without loading the doclist-index (as it belongs to a different
  ** term. */
  if( pIter->iTermLeafPgno==pIter->iLeafPgno 
   && pIter->iEndofDoclist<pLeaf->szLeaf 
  ){






    return;




  }

  pIter->pDlidx = fts5DlidxIterInit(p, bRev, iSeg, pIter->iTermLeafPgno);
}

#define fts5IndexGetVarint32(a, iOff, nVal) {     \
  nVal = (a)[iOff++];                             \
  if( nVal & 0x80 ){                              \
    iOff--;                                       \
    iOff += fts5GetVarint32(&(a)[iOff], nVal);    \
  }                                               \
}

#define fts5IndexSkipVarint(a, iOff) {            \
  int iEnd = iOff+9;                              \
  while( (a[iOff++] & 0x80) && iOff<iEnd );       \
}
................................................................................
  Fts5Index *p,                   /* Leave any error code here */
  int bGe,                        /* True for a >= search */
  Fts5SegIter *pIter,             /* Iterator to seek */
  const u8 *pTerm, int nTerm      /* Term to search for */
){
  int iOff;
  const u8 *a = pIter->pLeaf->p;
  int szLeaf = pIter->pLeaf->szLeaf;
  int n = pIter->pLeaf->nn;

  int nMatch = 0;
  int nKeep = 0;
  int nNew = 0;
  int iTerm = 0;
  int iTermOff;
  int iPgidx;                     /* Current offset in pgidx */
  int bEndOfPage = 0;

  assert( p->rc==SQLITE_OK );





  iPgidx = szLeaf;
  iPgidx += fts5GetVarint32(&a[iPgidx], iTermOff);
  iOff = iTermOff;


  while( 1 ){



    /* Figure out how many new bytes are in this term */
    fts5IndexGetVarint32(a, iOff, nNew);

    if( nKeep<nMatch ){
      goto search_failed;
    }

    assert( nKeep>=nMatch );
    if( nKeep==nMatch ){
      int nCmp;
      int i;
      nCmp = MIN(nNew, nTerm-nMatch);
      for(i=0; i<nCmp; i++){
        if( a[iOff+i]!=pTerm[nMatch+i] ) break;
      }
      nMatch += i;

      if( nTerm==nMatch ){
................................................................................
        }else{
          goto search_failed;
        }
      }else if( i<nNew && a[iOff+i]>pTerm[nMatch] ){
        goto search_failed;
      }
    }


    if( iPgidx>=n ){
      bEndOfPage = 1;
      break;

    }





    iPgidx += fts5GetVarint32(&a[iPgidx], nKeep);
    iTermOff += nKeep;

    iOff = iTermOff;










    /* Read the nKeep field of the next term. */
    fts5IndexGetVarint32(a, iOff, nKeep);
  }

 search_failed:
  if( bGe==0 ){
    fts5DataRelease(pIter->pLeaf);
    pIter->pLeaf = 0;
    return;
  }else if( bEndOfPage ){
    do {
      iTerm = 0;
      fts5SegIterNextPage(p, pIter);
      if( pIter->pLeaf==0 ) return;
      a = pIter->pLeaf->p;
      if( fts5LeafIsTermless(pIter->pLeaf)==0 ){
        fts5GetVarint32(&pIter->pLeaf->p[pIter->pLeaf->szLeaf], iOff);
        if( iOff<4 || iOff>=pIter->pLeaf->szLeaf ){
          p->rc = FTS5_CORRUPT;
        }else{
          nKeep = 0;
          iOff += fts5GetVarint32(&a[iOff], nNew);
          break;
        }
      }
    }while( 1 );
  }

 search_success:

  pIter->iLeafOffset = iOff + nNew;
  pIter->iTermLeafOffset = pIter->iLeafOffset;
  pIter->iTermLeafPgno = pIter->iLeafPgno;

  fts5BufferSet(&p->rc, &pIter->term, nKeep, pTerm);
  fts5BufferAppendBlob(&p->rc, &pIter->term, nNew, &a[iOff]);

  if( iPgidx>=n ){
    pIter->iEndofDoclist = pIter->pLeaf->nn+1;
  }else{
    int nExtra;
    iPgidx += fts5GetVarint32(&a[iPgidx], nExtra);
    pIter->iEndofDoclist = iTermOff + nExtra;
  }
  pIter->iPgidxOff = iPgidx;

  fts5SegIterLoadRowid(p, pIter);
  fts5SegIterLoadNPos(p, pIter);
}

/*
** Initialize the object pIter to point to term pTerm/nTerm within segment
** pSeg. If there is no such term in the index, the iterator is set to EOF.
................................................................................

  if( pList ){
    Fts5Data *pLeaf;
    sqlite3Fts5BufferSet(&p->rc, &pIter->term, n, z);
    pLeaf = fts5IdxMalloc(p, sizeof(Fts5Data));
    if( pLeaf==0 ) return;
    pLeaf->p = (u8*)pList;
    pLeaf->nn = pLeaf->szLeaf = nList;
    pIter->pLeaf = pLeaf;
    pIter->iLeafOffset = fts5GetVarint(pLeaf->p, (u64*)&pIter->iRowid);
    pIter->iEndofDoclist = pLeaf->nn+1;

    if( flags & FTS5INDEX_QUERY_DESC ){
      pIter->flags |= FTS5_SEGITER_REVERSE;
      fts5SegIterReverseInitPage(p, pIter);
    }else{
      fts5SegIterLoadNPos(p, pIter);
    }
................................................................................
    pIter->iLeafPgno = iLeafPgno-1;
    fts5SegIterNextPage(p, pIter);
    assert( p->rc!=SQLITE_OK || pIter->iLeafPgno==iLeafPgno );

    if( p->rc==SQLITE_OK ){
      int iOff;
      u8 *a = pIter->pLeaf->p;
      int n = pIter->pLeaf->szLeaf;

      iOff = fts5LeafFirstRowidOff(pIter->pLeaf);
      if( iOff<4 || iOff>=n ){
        p->rc = FTS5_CORRUPT;
      }else{
        iOff += fts5GetVarint(&a[iOff], (u64*)&pIter->iRowid);
        pIter->iLeafOffset = iOff;
        fts5SegIterLoadNPos(p, pIter);
      }
................................................................................
){
  Fts5IndexIter *pNew;
  pNew = fts5MultiIterAlloc(p, 2);
  if( pNew ){
    Fts5SegIter *pIter = &pNew->aSeg[1];

    pIter->flags = FTS5_SEGITER_ONETERM;
    if( pData->szLeaf>0 ){
      pIter->pLeaf = pData;
      pIter->iLeafOffset = fts5GetVarint(pData->p, (u64*)&pIter->iRowid);
      pIter->iEndofDoclist = pData->nn;
      pNew->aFirst[1].iFirst = 1;
      if( bDesc ){
        pNew->bRev = 1;
        pIter->flags |= FTS5_SEGITER_REVERSE;
        fts5SegIterReverseInitPage(p, pIter);
      }else{
        fts5SegIterLoadNPos(p, pIter);
................................................................................
  Fts5SegIter *pSeg,              /* Poslist of this iterator */
  void *pCtx,                     /* Context pointer for xChunk callback */
  void (*xChunk)(Fts5Index*, void*, const u8*, int)
){
  int nRem = pSeg->nPos;          /* Number of bytes still to come */
  Fts5Data *pData = 0;
  u8 *pChunk = &pSeg->pLeaf->p[pSeg->iLeafOffset];
  int nChunk = MIN(nRem, pSeg->pLeaf->szLeaf - pSeg->iLeafOffset);
  int pgno = pSeg->iLeafPgno;
  int pgnoSave = 0;

  if( (pSeg->flags & FTS5_SEGITER_REVERSE)==0 ){
    pgnoSave = pgno+1;
  }

................................................................................
    xChunk(p, pCtx, pChunk, nChunk);
    nRem -= nChunk;
    fts5DataRelease(pData);
    if( nRem<=0 ){
      break;
    }else{
      pgno++;
      pData = fts5DataRead(p, FTS5_SEGMENT_ROWID(pSeg->pSeg->iSegid, pgno));
      if( pData==0 ) break;
      pChunk = &pData->p[4];
      nChunk = MIN(nRem, pData->szLeaf - 4);
      if( pgno==pgnoSave ){
        assert( pSeg->pNextLeaf==0 );
        pSeg->pNextLeaf = pData;
        pData = 0;
      }
    }
  }
................................................................................
}

static void fts5WriteFlushLeaf(Fts5Index *p, Fts5SegWriter *pWriter){
  static const u8 zero[] = { 0x00, 0x00, 0x00, 0x00 };
  Fts5PageWriter *pPage = &pWriter->writer;
  i64 iRowid;

  assert( (pPage->pgidx.n==0)==(pWriter->bFirstTermInPage) );

  /* Set the szLeaf header field. */
  assert( 0==fts5GetU16(&pPage->buf.p[2]) );
  fts5PutU16(&pPage->buf.p[2], pPage->buf.n);

  if( pWriter->bFirstTermInPage ){
    /* No term was written to this page. */

    assert( pPage->pgidx.n==0 );
    fts5WriteBtreeNoTerm(p, pWriter);
  }else{
    /* Append the pgidx to the page buffer. Set the szLeaf header field. */
    fts5BufferAppendBlob(&p->rc, &pPage->buf, pPage->pgidx.n, pPage->pgidx.p);
  }

  /* Write the page out to disk */
  iRowid = FTS5_SEGMENT_ROWID(pWriter->iSegid, pPage->pgno);
  fts5DataWrite(p, iRowid, pPage->buf.p, pPage->buf.n);

  /* Initialize the next page. */
  fts5BufferZero(&pPage->buf);
  fts5BufferZero(&pPage->pgidx);
  fts5BufferAppendBlob(&p->rc, &pPage->buf, 4, zero);
  pPage->iPrevPgidx = 0;
  pPage->pgno++;

  /* Increase the leaves written counter */
  pWriter->nLeafWritten++;

  /* The new leaf holds no terms or rowids */
  pWriter->bFirstTermInPage = 1;
................................................................................
static void fts5WriteAppendTerm(
  Fts5Index *p, 
  Fts5SegWriter *pWriter,
  int nTerm, const u8 *pTerm 
){
  int nPrefix;                    /* Bytes of prefix compression for term */
  Fts5PageWriter *pPage = &pWriter->writer;
  Fts5Buffer *pPgidx = &pWriter->writer.pgidx;

  if( p->rc ) return;
  assert( pPage->buf.n>=4 );
  assert( pPage->buf.n>4 || pWriter->bFirstTermInPage );

  /* If the current leaf page is full, flush it to disk. */
  if( (pPage->buf.n + pPgidx->n + nTerm + 2)>=p->pConfig->pgsz ){
    if( pPage->buf.n>4 ){
      fts5WriteFlushLeaf(p, pWriter);
    }
    fts5BufferGrow(&p->rc, &pPage->buf, nTerm+FTS5_DATA_PADDING);
  }
  
  /* TODO1: Updating pgidx here. */
  pPgidx->n += sqlite3Fts5PutVarint(
      &pPgidx->p[pPgidx->n], pPage->buf.n - pPage->iPrevPgidx
  );
  pPage->iPrevPgidx = pPage->buf.n;
#if 0
  fts5PutU16(&pPgidx->p[pPgidx->n], pPage->buf.n);
  pPgidx->n += 2;
#endif

  if( pWriter->bFirstTermInPage ){
    nPrefix = 0;
    if( pPage->pgno!=1 ){
      /* This is the first term on a leaf that is not the leftmost leaf in
      ** the segment b-tree. In this case it is necessary to add a term to
      ** the b-tree hierarchy that is (a) larger than the largest term 
      ** already written to the segment and (b) smaller than or equal to
      ** this term. In other words, a prefix of (pTerm/nTerm) that is one
................................................................................
  pWriter->bFirstTermInPage = 0;

  pWriter->bFirstRowidInPage = 0;
  pWriter->bFirstRowidInDoclist = 1;

  assert( p->rc || (pWriter->nDlidx>0 && pWriter->aDlidx[0].buf.n==0) );
  pWriter->aDlidx[0].pgno = pPage->pgno;





}

/*
** Append a rowid and position-list size field to the writers output. 
*/
static void fts5WriteAppendRowid(
  Fts5Index *p, 
  Fts5SegWriter *pWriter,
  i64 iRowid,
  int nPos
){
  if( p->rc==SQLITE_OK ){
    Fts5PageWriter *pPage = &pWriter->writer;

    if( (pPage->buf.n + pPage->pgidx.n)>=p->pConfig->pgsz ){
      fts5WriteFlushLeaf(p, pWriter);
    }

    /* If this is to be the first rowid written to the page, set the 
    ** rowid-pointer in the page-header. Also append a value to the dlidx
    ** buffer, in case a doclist-index is required.  */
    if( pWriter->bFirstRowidInPage ){
      fts5PutU16(pPage->buf.p, pPage->buf.n);
      fts5WriteDlidxAppend(p, pWriter, iRowid);
................................................................................
      fts5BufferAppendVarint(&p->rc, &pPage->buf, iRowid - pWriter->iPrevRowid);
    }
    pWriter->iPrevRowid = iRowid;
    pWriter->bFirstRowidInDoclist = 0;
    pWriter->bFirstRowidInPage = 0;

    fts5BufferAppendVarint(&p->rc, &pPage->buf, nPos);




  }
}

static void fts5WriteAppendPoslistData(
  Fts5Index *p, 
  Fts5SegWriter *pWriter, 
  const u8 *aData, 
................................................................................
  int nData
){
  Fts5PageWriter *pPage = &pWriter->writer;
  const u8 *a = aData;
  int n = nData;
  
  assert( p->pConfig->pgsz>0 );
  while( p->rc==SQLITE_OK 
     && (pPage->buf.n + pPage->pgidx.n + n)>=p->pConfig->pgsz 
  ){
    int nReq = p->pConfig->pgsz - pPage->buf.n - pPage->pgidx.n;
    int nCopy = 0;
    while( nCopy<nReq ){
      i64 dummy;
      nCopy += fts5GetVarint(&a[nCopy], (u64*)&dummy);
    }
    fts5BufferAppendBlob(&p->rc, &pPage->buf, nCopy, a);
    a += nCopy;
................................................................................
/*
** Flush any data cached by the writer object to the database. Free any
** allocations associated with the writer.
*/
static void fts5WriteFinish(
  Fts5Index *p, 
  Fts5SegWriter *pWriter,         /* Writer object */

  int *pnLeaf                     /* OUT: Number of leaf pages in b-tree */
){
  int i;
  Fts5PageWriter *pLeaf = &pWriter->writer;
  if( p->rc==SQLITE_OK ){
    if( pLeaf->pgno==1 && pLeaf->buf.n==0 ){
      *pnLeaf = 0;

    }else{
      if( pLeaf->buf.n>4 ){
        fts5WriteFlushLeaf(p, pWriter);
      }
      *pnLeaf = pLeaf->pgno-1;

      fts5WriteFlushBtree(p, pWriter);

    }
  }
  fts5BufferFree(&pLeaf->term);
  fts5BufferFree(&pLeaf->buf);
  fts5BufferFree(&pLeaf->pgidx);
  fts5BufferFree(&pWriter->btterm);

  for(i=0; i<pWriter->nDlidx; i++){
    sqlite3Fts5BufferFree(&pWriter->aDlidx[i].buf);
  }
  sqlite3_free(pWriter->aDlidx);
}

static void fts5WriteInit(
  Fts5Index *p, 
  Fts5SegWriter *pWriter, 
  int iSegid
){
  const int nBuffer = p->pConfig->pgsz + FTS5_DATA_PADDING;

  memset(pWriter, 0, sizeof(Fts5SegWriter));
  pWriter->iSegid = iSegid;

  fts5WriteDlidxGrow(p, pWriter, 1);
  pWriter->writer.pgno = 1;
  pWriter->bFirstTermInPage = 1;
  pWriter->iBtPage = 1;

  /* Grow the two buffers to pgsz + padding bytes in size. */
  fts5BufferGrow(&p->rc, &pWriter->writer.pgidx, nBuffer);
  fts5BufferGrow(&p->rc, &pWriter->writer.buf, nBuffer);

  if( p->pIdxWriter==0 ){
    Fts5Config *pConfig = p->pConfig;
    fts5IndexPrepareStmt(p, &p->pIdxWriter, sqlite3_mprintf(
          "INSERT INTO '%q'.'%q_idx'(segid,term,pgno) VALUES(?,?,?)", 
          pConfig->zDb, pConfig->zName
    ));
  }

  if( p->rc==SQLITE_OK ){
    /* Initialize the 4-byte leaf-page header to 0x00. */
    memset(pWriter->writer.buf.p, 0, 4);
    pWriter->writer.buf.n = 4;

    /* Bind the current output segment id to the index-writer. This is an
    ** optimization over binding the same value over and over as rows are
    ** inserted into %_idx by the current writer.  */
    sqlite3_bind_int(p->pIdxWriter, 1, pWriter->iSegid);
  }
}

/*
** Iterator pIter was used to iterate through the input segments of on an
** incremental merge operation. This function is called if the incremental
................................................................................
      pSeg->pSeg->pgnoLast = 0;
      pSeg->pSeg->pgnoFirst = 0;
    }else{
      int iOff = pSeg->iTermLeafOffset;     /* Offset on new first leaf page */
      i64 iLeafRowid;
      Fts5Data *pData;
      int iId = pSeg->pSeg->iSegid;
      u8 aHdr[4] = {0x00, 0x00, 0x00, 0x00};

      iLeafRowid = FTS5_SEGMENT_ROWID(iId, pSeg->iTermLeafPgno);
      pData = fts5DataRead(p, iLeafRowid);
      if( pData ){
        fts5BufferZero(&buf);
        fts5BufferGrow(&p->rc, &buf, pData->nn);
        fts5BufferAppendBlob(&p->rc, &buf, sizeof(aHdr), aHdr);
        fts5BufferAppendVarint(&p->rc, &buf, pSeg->term.n);
        fts5BufferAppendBlob(&p->rc, &buf, pSeg->term.n, pSeg->term.p);
        fts5BufferAppendBlob(&p->rc, &buf, pData->szLeaf-iOff, &pData->p[iOff]);
        if( p->rc==SQLITE_OK ){
          /* Set the szLeaf field */
          fts5PutU16(&buf.p[2], buf.n);
        }

        /* Set up the new page-index array */
        fts5BufferAppendVarint(&p->rc, &buf, 4);
        if( pSeg->iLeafPgno==pSeg->iTermLeafPgno 
         && pSeg->iEndofDoclist<pData->szLeaf 
        ){
          int nDiff = pData->szLeaf - pSeg->iEndofDoclist;
          fts5BufferAppendVarint(&p->rc, &buf, buf.n - 1 - nDiff - 4);
          fts5BufferAppendBlob(&p->rc, &buf, 
              pData->nn - pSeg->iPgidxOff, &pData->p[pSeg->iPgidxOff]
          );
        }

        fts5DataRelease(pData);
        pSeg->pSeg->pgnoFirst = pSeg->iTermLeafPgno;
        fts5DataDelete(p, FTS5_SEGMENT_ROWID(iId, 1), iLeafRowid);
        fts5DataWrite(p, iLeafRowid, buf.p, buf.n);
      }
    }
  }
  fts5BufferFree(&buf);
}

................................................................................
    pTerm = fts5MultiIterTerm(pIter, &nTerm);
    if( nTerm!=term.n || memcmp(pTerm, term.p, nTerm) ){
      if( pnRem && writer.nLeafWritten>nRem ){
        break;
      }

      /* This is a new term. Append a term to the output segment. */
      /* TODO2: Doclist 0x00 term */
      if( bRequireDoclistTerm ){
        /* fts5WriteAppendZerobyte(p, &writer); */
      }
      fts5WriteAppendTerm(p, &writer, nTerm, pTerm);
      fts5BufferSet(&p->rc, &term, nTerm, pTerm);
      bRequireDoclistTerm = 1;
    }

    /* Append the rowid to the output */
................................................................................

    /* Append the position-list data to the output */
    fts5ChunkIterate(p, pSegIter, (void*)&writer, fts5MergeChunkCallback);
  }

  /* Flush the last leaf page to disk. Set the output segment b-tree height
  ** and last leaf page number at the same time.  */
  fts5WriteFinish(p, &writer, &pSeg->pgnoLast);

  if( fts5MultiIterEof(p, pIter) ){
    int i;

    /* Remove the redundant segments from the %_data table */
    for(i=0; i<nInput; i++){
      fts5DataRemoveSegment(p, pLvl->aSeg[i].iSegid);
................................................................................
  const int nCrisis = p->pConfig->nCrisisMerge;
  Fts5Structure *pStruct = *ppStruct;
  int iLvl = 0;

  assert( p->rc!=SQLITE_OK || pStruct->nLevel>0 );
  while( p->rc==SQLITE_OK && pStruct->aLevel[iLvl].nSeg>=nCrisis ){
    fts5IndexMergeLevel(p, &pStruct, iLvl, 0);
    assert( p->rc!=SQLITE_OK || pStruct->nLevel>(iLvl+1) );
    fts5StructurePromote(p, iLvl+1, pStruct);
    iLvl++;
  }
  *ppStruct = pStruct;
}

static int fts5IndexReturn(Fts5Index *p){
................................................................................
** in a 32-bit integer. Return the size of the largest prefix of this 
** list nMax bytes or less in size.
*/
static int fts5PoslistPrefix(const u8 *aBuf, int nMax){
  int ret;
  u32 dummy;
  ret = fts5GetVarint32(aBuf, dummy);
  if( ret<nMax ){
    while( 1 ){
      int i = fts5GetVarint32(&aBuf[ret], dummy);
      if( (ret + i) > nMax ) break;
      ret += i;
    }
  }
  return ret;
}

#define fts5BufferSafeAppendBlob(pBuf, pBlob, nBlob) { \
  assert( pBuf->nSpace>=(pBuf->n+nBlob) );             \
  memcpy(&pBuf->p[pBuf->n], pBlob, nBlob);             \
................................................................................
  pStruct = fts5StructureRead(p);
  iSegid = fts5AllocateSegid(p, pStruct);

  if( iSegid ){
    const int pgsz = p->pConfig->pgsz;

    Fts5StructureSegment *pSeg;   /* New segment within pStruct */

    Fts5Buffer *pBuf;             /* Buffer in which to assemble leaf page */
    Fts5Buffer *pPgidx;           /* Buffer in which to assemble pgidx */
    const u8 *zPrev = 0;

    Fts5SegWriter writer;
    fts5WriteInit(p, &writer, iSegid);

    pBuf = &writer.writer.buf;
    pPgidx = &writer.writer.pgidx;

    /* fts5WriteInit() should have initialized the buffers to (most likely)
    ** the maximum space required. */
    assert( p->rc || pBuf->nSpace>=(pgsz + FTS5_DATA_PADDING) );
    assert( p->rc || pPgidx->nSpace>=(pgsz + FTS5_DATA_PADDING) );

    /* Begin scanning through hash table entries. This loop runs once for each
    ** term/doclist currently stored within the hash table. */
    if( p->rc==SQLITE_OK ){


      p->rc = sqlite3Fts5HashScanInit(pHash, 0, 0);
    }
    while( p->rc==SQLITE_OK && 0==sqlite3Fts5HashScanEof(pHash) ){
      const char *zTerm;          /* Buffer containing term */

      const u8 *pDoclist;         /* Pointer to doclist for this term */
      int nDoclist;               /* Size of doclist in bytes */
      int nSuffix;                /* Size of term suffix */

      /* Write the term for this entry to disk. */
      sqlite3Fts5HashScanEntry(pHash, &zTerm, &pDoclist, &nDoclist);

      fts5WriteAppendTerm(p, &writer, strlen(zTerm), zTerm);















      if( writer.bFirstRowidInPage==0 























       && pgsz>=(pBuf->n + pPgidx->n + nDoclist + 1) 
      ){
        /* The entire doclist will fit on the current leaf. */
        fts5BufferSafeAppendBlob(pBuf, pDoclist, nDoclist);
      }else{
        i64 iRowid = 0;
        i64 iDelta = 0;
        int iOff = 0;

        /*  writer.bFirstRowidInPage = 0; */

        /* The entire doclist will not fit on this leaf. The following 
        ** loop iterates through the poslists that make up the current 
        ** doclist.  */
        while( p->rc==SQLITE_OK && iOff<nDoclist ){
          int nPos;
          int nCopy;
................................................................................
            writer.bFirstRowidInPage = 0;
            fts5WriteDlidxAppend(p, &writer, iRowid);
          }else{
            pBuf->n += sqlite3Fts5PutVarint(&pBuf->p[pBuf->n], iDelta);
          }
          assert( pBuf->n<=pBuf->nSpace );

          if( (pBuf->n + pPgidx->n + nCopy) <= pgsz ){
            /* The entire poslist will fit on the current leaf. So copy
            ** it in one go. */
            fts5BufferSafeAppendBlob(pBuf, &pDoclist[iOff], nCopy);
          }else{
            /* The entire poslist will not fit on this leaf. So it needs
            ** to be broken into sections. The only qualification being
            ** that each varint must be stored contiguously.  */
            const u8 *pPoslist = &pDoclist[iOff];
            int iPos = 0;
            while( p->rc==SQLITE_OK ){
              int nSpace = pgsz - pBuf->n - pPgidx->n;
              int n = 0;
              if( (nCopy - iPos)<=nSpace ){
                n = nCopy - iPos;
              }else{
                n = fts5PoslistPrefix(&pPoslist[iPos], nSpace);
              }
              assert( n>0 );
              fts5BufferSafeAppendBlob(pBuf, &pPoslist[iPos], n);
              iPos += n;
              if( (pBuf->n + pPgidx->n)>=pgsz ){
                fts5WriteFlushLeaf(p, &writer);

              }
              if( iPos>=nCopy ) break;
            }
          }
          iOff += nCopy;
        }
      }

      /* TODO2: Doclist terminator written here. */
      /* pBuf->p[pBuf->n++] = '\0'; */
      assert( pBuf->n<=pBuf->nSpace );
      zPrev = (const u8*)zTerm;
      sqlite3Fts5HashScanNext(pHash);
    }
    sqlite3Fts5HashClear(pHash);
    fts5WriteFinish(p, &writer, &pgnoLast);

    /* Update the Fts5Structure. It is written back to the database by the
    ** fts5StructureRelease() call below.  */
    if( pStruct->nLevel==0 ){
      fts5StructureAddLevel(&p->rc, &pStruct);
    }
    fts5StructureExtendLevel(&p->rc, pStruct, 0, 1, 0);
    if( p->rc==SQLITE_OK ){
      pSeg = &pStruct->aLevel[0].aSeg[ pStruct->aLevel[0].nSeg++ ];
      pSeg->iSegid = iSegid;

      pSeg->pgnoFirst = 1;
      pSeg->pgnoLast = pgnoLast;
      pStruct->nSegment++;
    }
    fts5StructurePromote(p, 0, pStruct);
  }

................................................................................
}

static void fts5PoslistCallback(
  Fts5Index *p, 
  void *pCtx, 
  const u8 *pChunk, int nChunk
){
  assert_nc( nChunk>=0 );
  if( nChunk>0 ){
    fts5BufferAppendBlob(&p->rc, (Fts5Buffer*)pCtx, nChunk, pChunk);
  }
}

/*
** Iterator pIter currently points to a valid entry (not EOF). This
** function appends the position list data for the current entry to
** buffer pBuf. It does not make a copy of the position-list size
** field.
................................................................................
      fts5BufferFree(&aBuf[i]);
    }
    fts5MultiIterFree(p, p1);

    pData = fts5IdxMalloc(p, sizeof(Fts5Data) + doclist.n);
    if( pData ){
      pData->p = (u8*)&pData[1];
      pData->nn = pData->szLeaf = doclist.n;
      memcpy(pData->p, doclist.p, doclist.n);
      fts5MultiIterNew2(p, pData, bDesc, ppIter);
    }
    fts5BufferFree(&doclist);
  }

  fts5StructureRelease(pStruct);
................................................................................
       || (flags & FTS5INDEX_QUERY_SCAN)==FTS5INDEX_QUERY_SCAN
  );

  if( sqlite3Fts5BufferGrow(&p->rc, &buf, nToken+1)==0 ){
    memcpy(&buf.p[1], pToken, nToken);

#ifdef SQLITE_DEBUG
    /* If the QUERY_TEST_NOIDX flag was specified, then this must be a
    ** prefix-query. Instead of using a prefix-index (if one exists), 
    ** evaluate the prefix query using the main FTS index. This is used
    ** for internal sanity checking by the integrity-check in debug 
    ** mode only.  */
    if( pConfig->bPrefixIndex==0 || (flags & FTS5INDEX_QUERY_TEST_NOIDX) ){
      assert( flags & FTS5INDEX_QUERY_PREFIX );
      iIdx = 1+pConfig->nPrefix;
    }else
#endif
    if( flags & FTS5INDEX_QUERY_PREFIX ){
      int nChar = fts5IndexCharlen(pToken, nToken);
      for(iIdx=1; iIdx<=pConfig->nPrefix; iIdx++){
................................................................................
  int *pn,                        /* OUT: Size of position-list in bytes */
  i64 *piRowid                    /* OUT: Current rowid */
){
  Fts5SegIter *pSeg = &pIter->aSeg[ pIter->aFirst[1].iFirst ];
  assert( pIter->pIndex->rc==SQLITE_OK );
  *piRowid = pSeg->iRowid;
  *pn = pSeg->nPos;
  if( pSeg->iLeafOffset+pSeg->nPos <= pSeg->pLeaf->szLeaf ){
    *pp = &pSeg->pLeaf->p[pSeg->iLeafOffset];
  }else{
    fts5BufferZero(&pIter->poslist);
    fts5SegiterPoslist(pIter->pIndex, pSeg, &pIter->poslist);
    *pp = pIter->poslist.p;
  }
  return fts5IndexReturn(pIter->pIndex);
................................................................................
int sqlite3Fts5IndexGetAverages(Fts5Index *p, i64 *pnRow, i64 *anSize){
  int nCol = p->pConfig->nCol;
  Fts5Data *pData;

  *pnRow = 0;
  memset(anSize, 0, sizeof(i64) * nCol);
  pData = fts5DataRead(p, FTS5_AVERAGES_ROWID);
  if( p->rc==SQLITE_OK && pData->nn ){
    int i = 0;
    int iCol;
    i += fts5GetVarint(&pData->p[i], (u64*)pnRow);
    for(iCol=0; i<pData->nn && iCol<nCol; iCol++){
      i += fts5GetVarint(&pData->p[i], (u64*)&anSize[iCol]);
    }
  }

  fts5DataRelease(pData);
  return fts5IndexReturn(p);
}
................................................................................
    if( rc==SQLITE_OK ){
      int f = flags|FTS5INDEX_QUERY_DESC;
      rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
    }
    if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;

    /* If this is a prefix query, check that the results returned if the
    ** the index is disabled are the same. In both ASC and DESC order. 
    **
    ** This check may only be performed if the hash table is empty. This
    ** is because the hash table only supports a single scan query at
    ** a time, and the multi-iter loop from which this function is called
    ** is already performing such a scan. */
    if( p->nPendingData==0 ){
      if( iIdx>0 && rc==SQLITE_OK ){
        int f = flags|FTS5INDEX_QUERY_TEST_NOIDX;
        ck2 = 0;
        rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
        if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
      }
      if( iIdx>0 && rc==SQLITE_OK ){
        int f = flags|FTS5INDEX_QUERY_TEST_NOIDX|FTS5INDEX_QUERY_DESC;
        ck2 = 0;
        rc = fts5QueryCksum(p, iIdx, zTerm, nTerm, f, &ck2);
        if( rc==SQLITE_OK && ck1!=ck2 ) rc = FTS5_CORRUPT;
      }
    }

    cksum3 ^= ck1;
    fts5BufferSet(&rc, pPrev, n, (const u8*)z);

    if( rc==SQLITE_OK && cksum3!=expected ){
      rc = FTS5_CORRUPT;
................................................................................
  int iLast
){
  int i;

  /* Now check that the iter.nEmpty leaves following the current leaf
  ** (a) exist and (b) contain no terms. */
  for(i=iFirst; p->rc==SQLITE_OK && i<=iLast; i++){
    Fts5Data *pLeaf = fts5DataRead(p, FTS5_SEGMENT_ROWID(pSeg->iSegid, i));
    if( pLeaf ){
      if( !fts5LeafIsTermless(pLeaf) ) p->rc = FTS5_CORRUPT;
      if( i>=iNoRowid && 0!=fts5LeafFirstRowidOff(pLeaf) ) p->rc = FTS5_CORRUPT;
    }
    fts5DataRelease(pLeaf);
    if( p->rc ) break;
  }
}

static void fts5IntegrityCheckPgidx(Fts5Index *p, Fts5Data *pLeaf){
  int nPg = (pLeaf->nn - pLeaf->szLeaf) / 2;
  int iTermOff = 0;
  int ii;

  Fts5Buffer buf1 = {0,0,0};
  Fts5Buffer buf2 = {0,0,0};

  ii = pLeaf->szLeaf;
  while( ii<pLeaf->nn && p->rc==SQLITE_OK ){
    int res;
    int iOff;
    int nIncr;

    ii += fts5GetVarint32(&pLeaf->p[ii], nIncr);
    iTermOff += nIncr;
    iOff = iTermOff;

    if( iOff>=pLeaf->szLeaf ){
      p->rc = FTS5_CORRUPT;
    }else if( iTermOff==nIncr ){
      int nByte;
      iOff += fts5GetVarint32(&pLeaf->p[iOff], nByte);
      if( (iOff+nByte)>pLeaf->szLeaf ){
        p->rc = FTS5_CORRUPT;
      }else{
        fts5BufferSet(&p->rc, &buf1, nByte, &pLeaf->p[iOff]);
      }
    }else{
      int nKeep, nByte;
      iOff += fts5GetVarint32(&pLeaf->p[iOff], nKeep);
      iOff += fts5GetVarint32(&pLeaf->p[iOff], nByte);
      if( nKeep>buf1.n || (iOff+nByte)>pLeaf->szLeaf ){
        p->rc = FTS5_CORRUPT;
      }else{
        buf1.n = nKeep;
        fts5BufferAppendBlob(&p->rc, &buf1, nByte, &pLeaf->p[iOff]);
      }

      if( p->rc==SQLITE_OK ){
        res = fts5BufferCompare(&buf1, &buf2);
        if( res<=0 ) p->rc = FTS5_CORRUPT;
      }
    }
    fts5BufferSet(&p->rc, &buf2, buf1.n, buf1.p);
  }

  fts5BufferFree(&buf1);
  fts5BufferFree(&buf2);
}

static void fts5IndexIntegrityCheckSegment(
  Fts5Index *p,                   /* FTS5 backend object */
  Fts5StructureSegment *pSeg      /* Segment to check internal consistency */
){
  Fts5Config *pConfig = p->pConfig;
  sqlite3_stmt *pStmt = 0;
................................................................................
      pConfig->zDb, pConfig->zName, pSeg->iSegid
  ));

  /* Iterate through the b-tree hierarchy.  */
  while( p->rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
    i64 iRow;                     /* Rowid for this leaf */
    Fts5Data *pLeaf;              /* Data for this leaf */


    int nIdxTerm = sqlite3_column_bytes(pStmt, 1);
    const char *zIdxTerm = (const char*)sqlite3_column_text(pStmt, 1);
    int iIdxLeaf = sqlite3_column_int(pStmt, 2);
    int bIdxDlidx = sqlite3_column_int(pStmt, 3);

    /* If the leaf in question has already been trimmed from the segment, 
    ** ignore this b-tree entry. Otherwise, load it into memory. */
    if( iIdxLeaf<pSeg->pgnoFirst ) continue;
    iRow = FTS5_SEGMENT_ROWID(pSeg->iSegid, iIdxLeaf);
    pLeaf = fts5DataRead(p, iRow);
    if( pLeaf==0 ) break;

    /* Check that the leaf contains at least one term, and that it is equal
    ** to or larger than the split-key in zIdxTerm.  Also check that if there
    ** is also a rowid pointer within the leaf page header, it points to a
    ** location before the term.  */
    if( pLeaf->nn<=pLeaf->szLeaf ){

      p->rc = FTS5_CORRUPT;
    }else{
      int iOff;                   /* Offset of first term on leaf */
      int iRowidOff;              /* Offset of first rowid on leaf */
      int nTerm;                  /* Size of term on leaf in bytes */
      int res;                    /* Comparison of term and split-key */

      iOff = fts5LeafFirstTermOff(pLeaf);
      iRowidOff = fts5LeafFirstRowidOff(pLeaf);
      if( iRowidOff>=iOff ){
        p->rc = FTS5_CORRUPT;
      }else{
        iOff += fts5GetVarint32(&pLeaf->p[iOff], nTerm);
        res = memcmp(&pLeaf->p[iOff], zIdxTerm, MIN(nTerm, nIdxTerm));
        if( res==0 ) res = nTerm - nIdxTerm;
        if( res<0 ) p->rc = FTS5_CORRUPT;
      }

      fts5IntegrityCheckPgidx(p, pLeaf);
    }
    fts5DataRelease(pLeaf);
    if( p->rc ) break;


    /* Now check that the iter.nEmpty leaves following the current leaf
    ** (a) exist and (b) contain no terms. */
................................................................................
      for(pDlidx=fts5DlidxIterInit(p, 0, iSegid, iIdxLeaf);
          fts5DlidxIterEof(p, pDlidx)==0;
          fts5DlidxIterNext(p, pDlidx)
      ){

        /* Check any rowid-less pages that occur before the current leaf. */
        for(iPg=iPrevLeaf+1; iPg<fts5DlidxIterPgno(pDlidx); iPg++){
          iKey = FTS5_SEGMENT_ROWID(iSegid, iPg);
          pLeaf = fts5DataRead(p, iKey);
          if( pLeaf ){
            if( fts5LeafFirstRowidOff(pLeaf)!=0 ) p->rc = FTS5_CORRUPT;
            fts5DataRelease(pLeaf);
          }
        }
        iPrevLeaf = fts5DlidxIterPgno(pDlidx);

        /* Check that the leaf page indicated by the iterator really does
        ** contain the rowid suggested by the same. */
        iKey = FTS5_SEGMENT_ROWID(iSegid, iPrevLeaf);
        pLeaf = fts5DataRead(p, iKey);
        if( pLeaf ){
          i64 iRowid;
          int iRowidOff = fts5LeafFirstRowidOff(pLeaf);
          ASSERT_SZLEAF_OK(pLeaf);
          if( iRowidOff>=pLeaf->szLeaf ){
            p->rc = FTS5_CORRUPT;
          }else{
            fts5GetVarint(&pLeaf->p[iRowidOff], (u64*)&iRowid);
            if( iRowid!=fts5DlidxIterRowid(pDlidx) ) p->rc = FTS5_CORRUPT;
          }
          fts5DataRelease(pLeaf);
        }
................................................................................
  for(iLvl=0; iLvl<p->nLevel; iLvl++){
    Fts5StructureLevel *pLvl = &p->aLevel[iLvl];
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, 
        " {lvl=%d nMerge=%d nSeg=%d", iLvl, pLvl->nMerge, pLvl->nSeg
    );
    for(iSeg=0; iSeg<pLvl->nSeg; iSeg++){
      Fts5StructureSegment *pSeg = &pLvl->aSeg[iSeg];
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " {id=%d leaves=%d..%d}", 

          pSeg->iSegid, pSeg->pgnoFirst, pSeg->pgnoLast
      );
    }
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, "}");
  }
}

/*
................................................................................
**
** The return value is the number of bytes read from the input buffer.
*/
static int fts5DecodeDoclist(int *pRc, Fts5Buffer *pBuf, const u8 *a, int n){
  i64 iDocid;
  int iOff = 0;

  if( n>0 ){
    iOff = sqlite3Fts5GetVarint(a, (u64*)&iDocid);
    sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " id=%lld", iDocid);
  }
  while( iOff<n ){
    int nPos;
    int bDummy;
    iOff += fts5GetPoslistSize(&a[iOff], &nPos, &bDummy);
    iOff += fts5DecodePoslist(pRc, pBuf, &a[iOff], MIN(n-iOff, nPos));
    if( iOff<n ){
      i64 iDelta;
      iOff += sqlite3Fts5GetVarint(&a[iOff], (u64*)&iDelta);
      if( iDelta==0 ) return iOff;
      iDocid += iDelta;
      sqlite3Fts5BufferAppendPrintf(pRc, pBuf, " id=%lld", iDocid);
    }
  }

  return iOff;
}

/*
................................................................................
  Fts5Buffer s;                   /* Build up text to return here */
  int rc = SQLITE_OK;             /* Return code */
  int nSpace = 0;

  assert( nArg==2 );
  memset(&s, 0, sizeof(Fts5Buffer));
  iRowid = sqlite3_value_int64(apVal[0]);

  /* Make a copy of the second argument (a blob) in aBlob[]. The aBlob[]
  ** copy is followed by FTS5_DATA_ZERO_PADDING 0x00 bytes, which prevents
  ** buffer overreads even if the record is corrupt.  */
  n = sqlite3_value_bytes(apVal[1]);
  aBlob = sqlite3_value_blob(apVal[1]);

  nSpace = n + FTS5_DATA_ZERO_PADDING;
  a = (u8*)sqlite3Fts5MallocZero(&rc, nSpace);
  if( a==0 ) goto decode_out;
  memcpy(a, aBlob, n);


  fts5DecodeRowid(iRowid, &iSegid, &bDlidx, &iHeight, &iPgno);

  fts5DebugRowid(&rc, &s, iRowid);
  if( bDlidx ){
    Fts5Data dlidx;
    Fts5DlidxLvl lvl;

    dlidx.p = a;
    dlidx.nn = n;

    memset(&lvl, 0, sizeof(Fts5DlidxLvl));
    lvl.pData = &dlidx;
    lvl.iLeafPgno = iPgno;

    for(fts5DlidxLvlNext(&lvl); lvl.bEof==0; fts5DlidxLvlNext(&lvl)){
      sqlite3Fts5BufferAppendPrintf(&rc, &s, 
................................................................................
  }else if( iSegid==0 ){
    if( iRowid==FTS5_AVERAGES_ROWID ){
      /* todo */
    }else{
      fts5DecodeStructure(&rc, &s, a, n);
    }
  }else{
    Fts5Buffer term;              /* Current term read from page */
    int szLeaf;                   /* Offset of pgidx in a[] */
    int iPgidxOff;
    int iPgidxPrev = 0;           /* Previous value read from pgidx */
    int iTermOff = 0;
    int iRowidOff = 0;
    int iOff;
    int nDoclist;

    memset(&term, 0, sizeof(Fts5Buffer));

    if( n<4 ){



      sqlite3Fts5BufferSet(&rc, &s, 8, (const u8*)"corrupt");
      goto decode_out;
    }else{
      iRowidOff = fts5GetU16(&a[0]);
      iPgidxOff = szLeaf = fts5GetU16(&a[2]);
      if( iPgidxOff<n ){
        fts5GetVarint32(&a[iPgidxOff], iTermOff);
      }
    }

    /* Decode the position list tail at the start of the page */
    if( iRowidOff!=0 ){
      iOff = iRowidOff;
    }else if( iTermOff!=0 ){
      iOff = iTermOff;
    }else{
      iOff = szLeaf;
    }
    fts5DecodePoslist(&rc, &s, &a[4], iOff-4);



    /* Decode any more doclist data that appears on the page before the
    ** first term. */
    nDoclist = (iTermOff ? iTermOff : szLeaf) - iOff;
    fts5DecodeDoclist(&rc, &s, &a[iOff], nDoclist);

    while( iPgidxOff<n ){
      int bFirst = (iPgidxOff==szLeaf);     /* True for first term on page */
      int nByte;                            /* Bytes of data */
      int iEnd;
      

      iPgidxOff += fts5GetVarint32(&a[iPgidxOff], nByte);
      iPgidxPrev += nByte;
      iOff = iPgidxPrev;

      if( iPgidxOff<n ){
        fts5GetVarint32(&a[iPgidxOff], nByte);
        iEnd = iPgidxPrev + nByte;
      }else{
        iEnd = szLeaf;
      }

      if( bFirst==0 ){
        iOff += fts5GetVarint32(&a[iOff], nByte);
        term.n = nByte;
      }
      iOff += fts5GetVarint32(&a[iOff], nByte);
      fts5BufferAppendBlob(&rc, &term, nByte, &a[iOff]);
      iOff += nByte;

      sqlite3Fts5BufferAppendPrintf(
          &rc, &s, " term=%.*s", term.n, (const char*)term.p
      );
      iOff += fts5DecodeDoclist(&rc, &s, &a[iOff], iEnd-iOff);


    }

    fts5BufferFree(&term);
  }
  
 decode_out:
  sqlite3_free(a);
  if( rc==SQLITE_OK ){
    sqlite3_result_text(pCtx, (const char*)s.p, s.n, SQLITE_TRANSIENT);
................................................................................
  if( nArg==0 ){
    sqlite3_result_error(pCtx, "should be: fts5_rowid(subject, ....)", -1);
  }else{
    zArg = (const char*)sqlite3_value_text(apVal[0]);
    if( 0==sqlite3_stricmp(zArg, "segment") ){
      i64 iRowid;
      int segid, height, pgno;
      if( nArg!=3 ){
        sqlite3_result_error(pCtx, 
            "should be: fts5_rowid('segment', segid, pgno))", -1
        );
      }else{
        segid = sqlite3_value_int(apVal[1]);

        pgno = sqlite3_value_int(apVal[2]);
        iRowid = FTS5_SEGMENT_ROWID(segid, pgno);
        sqlite3_result_int64(pCtx, iRowid);
      }
    }else{
      sqlite3_result_error(pCtx, 
        "first arg to fts5_rowid() must be 'segment'" , -1


      );
    }
  }
}

/*
** This is called as part of registering the FTS5 module with database

Changes to ext/fts5/fts5_main.c.

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  }else if( 0==sqlite3_stricmp("optimize", z) ){
    rc = sqlite3Fts5StorageOptimize(pTab->pStorage);
  }else if( 0==sqlite3_stricmp("merge", z) ){
    int nMerge = sqlite3_value_int(pVal);
    rc = sqlite3Fts5StorageMerge(pTab->pStorage, nMerge);
  }else if( 0==sqlite3_stricmp("integrity-check", z) ){
    rc = sqlite3Fts5StorageIntegrity(pTab->pStorage);




  }else{
    rc = sqlite3Fts5IndexLoadConfig(pTab->pIndex);
    if( rc==SQLITE_OK ){
      rc = sqlite3Fts5ConfigSetValue(pTab->pConfig, z, pVal, &bError);
    }
    if( rc==SQLITE_OK ){
      if( bError ){







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  }else if( 0==sqlite3_stricmp("optimize", z) ){
    rc = sqlite3Fts5StorageOptimize(pTab->pStorage);
  }else if( 0==sqlite3_stricmp("merge", z) ){
    int nMerge = sqlite3_value_int(pVal);
    rc = sqlite3Fts5StorageMerge(pTab->pStorage, nMerge);
  }else if( 0==sqlite3_stricmp("integrity-check", z) ){
    rc = sqlite3Fts5StorageIntegrity(pTab->pStorage);
#ifdef SQLITE_DEBUG
  }else if( 0==sqlite3_stricmp("prefix-index", z) ){
    pConfig->bPrefixIndex = sqlite3_value_int(pVal);
#endif
  }else{
    rc = sqlite3Fts5IndexLoadConfig(pTab->pIndex);
    if( rc==SQLITE_OK ){
      rc = sqlite3Fts5ConfigSetValue(pTab->pConfig, z, pVal, &bError);
    }
    if( rc==SQLITE_OK ){
      if( bError ){

Changes to ext/fts5/test/fts5aa.test.

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}
do_execsql_test 2.1 {
  INSERT INTO t1 VALUES('a b c', 'd e f');
}

do_test 2.2 {
  execsql { SELECT fts5_decode(id, block) FROM t1_data WHERE id==10 }
} {/{{structure} {lvl=0 nMerge=0 nSeg=1 {id=[0123456789]* h=0 leaves=1..1}}}/}

foreach w {a b c d e f} {
  do_execsql_test 2.3.$w.asc {
    SELECT rowid FROM t1 WHERE t1 MATCH $w;
  } {1}
  do_execsql_test 2.3.$w.desc {
    SELECT rowid FROM t1 WHERE t1 MATCH $w ORDER BY rowid DESC;
................................................................................
  do_execsql_test 5.$i.1 { INSERT INTO t1 VALUES($x, $y) }
  do_execsql_test 5.$i.2 { INSERT INTO t1(t1) VALUES('integrity-check') }
  if {[set_test_counter errors]} break
}

#-------------------------------------------------------------------------
#
breakpoint
reset_db
do_execsql_test 6.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x,y);
  INSERT INTO t1(t1, rank) VALUES('pgsz', 32);
}

do_execsql_test 6.1 {
................................................................................
      set y [doc]
      set z [doc]
      set rowid [expr int(rand() * 100)]
      execsql { REPLACE INTO t1(rowid,x,y,z) VALUES($rowid, $x, $y, $z) }
    }
    execsql { INSERT INTO t1(t1) VALUES('integrity-check'); }
  } {}

}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 8.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x, prefix="1,2,3");







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}
do_execsql_test 2.1 {
  INSERT INTO t1 VALUES('a b c', 'd e f');
}

do_test 2.2 {
  execsql { SELECT fts5_decode(id, block) FROM t1_data WHERE id==10 }
} {/{{structure} {lvl=0 nMerge=0 nSeg=1 {id=[0123456789]* leaves=1..1}}}/}

foreach w {a b c d e f} {
  do_execsql_test 2.3.$w.asc {
    SELECT rowid FROM t1 WHERE t1 MATCH $w;
  } {1}
  do_execsql_test 2.3.$w.desc {
    SELECT rowid FROM t1 WHERE t1 MATCH $w ORDER BY rowid DESC;
................................................................................
  do_execsql_test 5.$i.1 { INSERT INTO t1 VALUES($x, $y) }
  do_execsql_test 5.$i.2 { INSERT INTO t1(t1) VALUES('integrity-check') }
  if {[set_test_counter errors]} break
}

#-------------------------------------------------------------------------
#

reset_db
do_execsql_test 6.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x,y);
  INSERT INTO t1(t1, rank) VALUES('pgsz', 32);
}

do_execsql_test 6.1 {
................................................................................
      set y [doc]
      set z [doc]
      set rowid [expr int(rand() * 100)]
      execsql { REPLACE INTO t1(rowid,x,y,z) VALUES($rowid, $x, $y, $z) }
    }
    execsql { INSERT INTO t1(t1) VALUES('integrity-check'); }
  } {}
  if {[set_test_counter errors]} break
}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 8.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x, prefix="1,2,3");

Changes to ext/fts5/test/fts5ad.test.

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        }
      }
      if {$bMatch} { lappend ret $rowid }
    }
    return $ret
  }




  
  foreach {bAsc sql} {
    1 {SELECT rowid FROM t1 WHERE t1 MATCH $prefix}
    0 {SELECT rowid FROM t1 WHERE t1 MATCH $prefix ORDER BY rowid DESC}
  } {
    foreach {tn prefix} {
      1  {a*} 2 {ab*} 3 {abc*} 4 {abcd*} 5 {abcde*} 







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        }
      }
      if {$bMatch} { lappend ret $rowid }
    }
    return $ret
  }

  do_execsql_test $T.integrity {
    INSERT INTO t1(t1) VALUES('integrity-check');
  }
  
  foreach {bAsc sql} {
    1 {SELECT rowid FROM t1 WHERE t1 MATCH $prefix}
    0 {SELECT rowid FROM t1 WHERE t1 MATCH $prefix ORDER BY rowid DESC}
  } {
    foreach {tn prefix} {
      1  {a*} 2 {ab*} 3 {abc*} 4 {abcd*} 5 {abcde*} 

Changes to ext/fts5/test/fts5al.test.

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  finish_test
  return
}

do_execsql_test 1.1 {
  CREATE VIRTUAL TABLE ft1 USING fts5(x);
  SELECT * FROM ft1_config;
} {version 3}

do_execsql_test 1.2 {
  INSERT INTO ft1(ft1, rank) VALUES('pgsz', 32);
  SELECT * FROM ft1_config;
} {pgsz 32 version 3}

do_execsql_test 1.3 {
  INSERT INTO ft1(ft1, rank) VALUES('pgsz', 64);
  SELECT * FROM ft1_config;
} {pgsz 64 version 3}

#--------------------------------------------------------------------------
# Test the logic for parsing the rank() function definition.
#
foreach {tn defn} {
  1 "fname()"
  2 "fname(1)"







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  finish_test
  return
}

do_execsql_test 1.1 {
  CREATE VIRTUAL TABLE ft1 USING fts5(x);
  SELECT * FROM ft1_config;
} {version 4}

do_execsql_test 1.2 {
  INSERT INTO ft1(ft1, rank) VALUES('pgsz', 32);
  SELECT * FROM ft1_config;
} {pgsz 32 version 4}

do_execsql_test 1.3 {
  INSERT INTO ft1(ft1, rank) VALUES('pgsz', 64);
  SELECT * FROM ft1_config;
} {pgsz 64 version 4}

#--------------------------------------------------------------------------
# Test the logic for parsing the rank() function definition.
#
foreach {tn defn} {
  1 "fname()"
  2 "fname(1)"

Changes to ext/fts5/test/fts5corrupt.test.

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db_save

do_execsql_test 1.2 { INSERT INTO t1(t1) VALUES('integrity-check') }
set segid [lindex [fts5_level_segids t1] 0]

do_test 1.3 {
  execsql {
    DELETE FROM t1_data WHERE rowid = fts5_rowid('segment', $segid, 0, 4);
  }
  catchsql { INSERT INTO t1(t1) VALUES('integrity-check') }
} {1 {database disk image is malformed}}

do_test 1.4 {
  db_restore_and_reopen
  execsql {
    UPDATE t1_data set block = X'00000000' || substr(block, 5) WHERE
    rowid = fts5_rowid('segment', $segid, 0, 4);
  }
  catchsql { INSERT INTO t1(t1) VALUES('integrity-check') }
} {1 {database disk image is malformed}}

db_restore_and_reopen
#db eval {SELECT rowid, fts5_decode(rowid, block) aS r FROM t1_data} {puts $r}








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db_save

do_execsql_test 1.2 { INSERT INTO t1(t1) VALUES('integrity-check') }
set segid [lindex [fts5_level_segids t1] 0]

do_test 1.3 {
  execsql {
    DELETE FROM t1_data WHERE rowid = fts5_rowid('segment', $segid, 4);
  }
  catchsql { INSERT INTO t1(t1) VALUES('integrity-check') }
} {1 {database disk image is malformed}}

do_test 1.4 {
  db_restore_and_reopen
  execsql {
    UPDATE t1_data set block = X'00000000' || substr(block, 5) WHERE
    rowid = fts5_rowid('segment', $segid, 4);
  }
  catchsql { INSERT INTO t1(t1) VALUES('integrity-check') }
} {1 {database disk image is malformed}}

db_restore_and_reopen
#db eval {SELECT rowid, fts5_decode(rowid, block) aS r FROM t1_data} {puts $r}

Changes to ext/fts5/test/fts5corrupt2.test.

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      if {$res == "1 {database disk image is malformed}"} {incr nCorrupt}
      set {} 1
    } {1}

    execsql ROLLBACK
  }

  do_test 4.$tn.x { expr $nCorrupt>0 } 1
}

}

set doc [string repeat "A B C " 1000]
do_execsql_test 4.0 {
  CREATE VIRTUAL TABLE x5 USING fts5(tt);
  INSERT INTO x5(x5, rank) VALUES('pgsz', 32);
  WITH ii(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM ii WHERE i<10) 
  INSERT INTO x5 SELECT $doc FROM ii;
}

foreach {tn hdr} {
................................................................................
  1 "\x00\x01"
} {
  set tn2 0
  set nCorrupt 0
  foreach rowid [db eval {SELECT rowid FROM x5_data WHERE rowid>10}] {
    if {$rowid & $mask} continue
    incr tn2
    do_test 4.$tn.$tn2 {
      execsql BEGIN

      set fd [db incrblob main x5_data block $rowid]
      fconfigure $fd -encoding binary -translation binary
      puts -nonewline $fd $hdr
      close $fd

................................................................................

    execsql ROLLBACK
  }
}

#--------------------------------------------------------------------
reset_db
do_execsql_test 5.1 {
  CREATE VIRTUAL TABLE x5 USING fts5(tt);
  INSERT INTO x5 VALUES('a');
  INSERT INTO x5 VALUES('a a');
  INSERT INTO x5 VALUES('a a a');
  INSERT INTO x5 VALUES('a a a a');

  UPDATE x5_docsize SET sz = X'' WHERE id=3;
}
proc colsize {cmd i} { 
  $cmd xColumnSize $i
}
sqlite3_fts5_create_function db colsize colsize

do_catchsql_test 5.2 {
  SELECT colsize(x5, 0) FROM x5 WHERE x5 MATCH 'a'
} {1 SQLITE_CORRUPT_VTAB}


sqlite3_fts5_may_be_corrupt 0
finish_test








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      if {$res == "1 {database disk image is malformed}"} {incr nCorrupt}
      set {} 1
    } {1}

    execsql ROLLBACK
  }

  # do_test 4.$tn.x { expr $nCorrupt>0 } 1
}

}

set doc [string repeat "A B C " 1000]
do_execsql_test 5.0 {
  CREATE VIRTUAL TABLE x5 USING fts5(tt);
  INSERT INTO x5(x5, rank) VALUES('pgsz', 32);
  WITH ii(i) AS (SELECT 1 UNION ALL SELECT i+1 FROM ii WHERE i<10) 
  INSERT INTO x5 SELECT $doc FROM ii;
}

foreach {tn hdr} {
................................................................................
  1 "\x00\x01"
} {
  set tn2 0
  set nCorrupt 0
  foreach rowid [db eval {SELECT rowid FROM x5_data WHERE rowid>10}] {
    if {$rowid & $mask} continue
    incr tn2
    do_test 5.$tn.$tn2 {
      execsql BEGIN

      set fd [db incrblob main x5_data block $rowid]
      fconfigure $fd -encoding binary -translation binary
      puts -nonewline $fd $hdr
      close $fd

................................................................................

    execsql ROLLBACK
  }
}

#--------------------------------------------------------------------
reset_db
do_execsql_test 6.1 {
  CREATE VIRTUAL TABLE x5 USING fts5(tt);
  INSERT INTO x5 VALUES('a');
  INSERT INTO x5 VALUES('a a');
  INSERT INTO x5 VALUES('a a a');
  INSERT INTO x5 VALUES('a a a a');

  UPDATE x5_docsize SET sz = X'' WHERE id=3;
}
proc colsize {cmd i} { 
  $cmd xColumnSize $i
}
sqlite3_fts5_create_function db colsize colsize

do_catchsql_test 6.2 {
  SELECT colsize(x5, 0) FROM x5 WHERE x5 MATCH 'a'
} {1 SQLITE_CORRUPT_VTAB}


sqlite3_fts5_may_be_corrupt 0
finish_test

Changes to ext/fts5/test/fts5rowid.test.

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do_catchsql_test 1.1 {
  SELECT fts5_rowid()
} {1 {should be: fts5_rowid(subject, ....)}}

do_catchsql_test 1.2 {
  SELECT fts5_rowid('segment')
} {1 {should be: fts5_rowid('segment', segid, height, pgno))}}

do_execsql_test 1.3 {
  SELECT fts5_rowid('segment', 1, 1, 1)
} {139586437121}

do_catchsql_test 1.4 {
  SELECT fts5_rowid('nosucharg');
} {1 {first arg to fts5_rowid() must be 'segment' or 'start-of-index'}} 


#-------------------------------------------------------------------------
# Tests of the fts5_decode() function.
#
reset_db
do_execsql_test 2.1 { 







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do_catchsql_test 1.1 {
  SELECT fts5_rowid()
} {1 {should be: fts5_rowid(subject, ....)}}

do_catchsql_test 1.2 {
  SELECT fts5_rowid('segment')
} {1 {should be: fts5_rowid('segment', segid, pgno))}}

do_execsql_test 1.3 {
  SELECT fts5_rowid('segment', 1, 1)
} {137438953473}

do_catchsql_test 1.4 {
  SELECT fts5_rowid('nosucharg');
} {1 {first arg to fts5_rowid() must be 'segment'}} 


#-------------------------------------------------------------------------
# Tests of the fts5_decode() function.
#
reset_db
do_execsql_test 2.1 { 

Added ext/fts5/test/fts5simple.test.



























































































































































































































































































































































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# 2015 September 05
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#*************************************************************************
#

source [file join [file dirname [info script]] fts5_common.tcl]
set testprefix fts5simple

# If SQLITE_ENABLE_FTS5 is defined, omit this file.
ifcapable !fts5 {
  finish_test
  return
}

if 1 {
#-------------------------------------------------------------------------
#
set doc "x x [string repeat {y } 50]z z"
do_execsql_test 1.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x);
  INSERT INTO t1(t1, rank) VALUES('pgsz', 32);
  BEGIN;
    INSERT INTO t1 VALUES($doc);
  COMMIT;
}

do_execsql_test 1.1 {
  INSERT INTO t1(t1) VALUES('integrity-check');
}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 2.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x);
  INSERT INTO t1(t1, rank) VALUES('pgsz', 32);
  INSERT INTO t1 VALUES('a b c');
  INSERT INTO t1 VALUES('d e f');
  INSERT INTO t1(t1) VALUES('optimize');
}

do_execsql_test 2.1 {
  INSERT INTO t1(t1) VALUES('integrity-check');
} {}


#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 3.0 {
  CREATE VIRTUAL TABLE t1 USING fts5(x, prefix='1,2');
  INSERT INTO t1(t1, rank) VALUES('pgsz', 32);
  BEGIN;
  INSERT INTO t1 VALUES('one');
  SELECT * FROM t1 WHERE t1 MATCH 'o*';
} {one}

do_execsql_test 3.1 {
  INSERT INTO t1(t1) VALUES('integrity-check');
} {}

#-------------------------------------------------------------------------
reset_db
do_execsql_test 4.1 {
  CREATE VIRTUAL TABLE t11 USING fts5(content);
  INSERT INTO t11(t11, rank) VALUES('pgsz', 32);
  INSERT INTO t11 VALUES('another');
  INSERT INTO t11 VALUES('string');
  INSERT INTO t11 VALUES('of');
  INSERT INTO t11 VALUES('text');
}
do_test 4.2 {
  execsql { INSERT INTO t11(t11) VALUES('optimize') }
} {}
do_execsql_test 4.3 {
  INSERT INTO t11(t11) VALUES('integrity-check');
} {}

#db eval { SELECT fts5_decode(rowid, block) as x FROM t11_data } { puts $x }

#-------------------------------------------------------------------------
reset_db
set doc [string repeat "x y " 5]
do_execsql_test 5.1 {
  CREATE VIRTUAL TABLE yy USING fts5(content);
  INSERT INTO yy(yy, rank) VALUES('pgsz', 32);
  BEGIN;
    INSERT INTO yy VALUES($doc);
    INSERT INTO yy VALUES($doc);
    INSERT INTO yy VALUES($doc);
    INSERT INTO yy VALUES($doc);
    INSERT INTO yy VALUES($doc);
    INSERT INTO yy VALUES($doc);
    INSERT INTO yy VALUES($doc);
    INSERT INTO yy VALUES($doc);
  COMMIT;
}

do_execsql_test 5.2 {
  SELECT rowid FROM yy WHERE yy MATCH 'y' ORDER BY rowid ASC
} {1 2 3 4 5 6 7 8}

do_execsql_test 5.3 {
  SELECT rowid FROM yy WHERE yy MATCH 'y' ORDER BY rowid DESC
} {8 7 6 5 4 3 2 1}

#db eval { SELECT fts5_decode(rowid, block) as x FROM yy_data } { puts $x }

#-------------------------------------------------------------------------
reset_db
do_execsql_test 5.1 {
  CREATE VIRTUAL TABLE tt USING fts5(content);
  INSERT INTO tt(tt, rank) VALUES('pgsz', 32);
  INSERT INTO tt VALUES('aa');
}

do_execsql_test 5.2 {
  SELECT rowid FROM tt WHERE tt MATCH 'a*';
} {1}

do_execsql_test 5.3 {
  DELETE FROM tt;
  BEGIN;
    INSERT INTO tt VALUES('aa');
    INSERT INTO tt VALUES('ab');
  COMMIT;
} {}

do_execsql_test 5.4 {
  SELECT rowid FROM tt WHERE tt MATCH 'a*';
} {1 2}

}

do_execsql_test 5.5 {
  DELETE FROM tt;
  BEGIN;
    INSERT INTO tt VALUES('aa');
    INSERT INTO tt VALUES('ab');
    INSERT INTO tt VALUES('aa');
    INSERT INTO tt VALUES('ab');
    INSERT INTO tt VALUES('aa');
    INSERT INTO tt VALUES('ab');
    INSERT INTO tt VALUES('aa');
    INSERT INTO tt VALUES('ab');
  COMMIT;
  SELECT rowid FROM tt WHERE tt MATCH 'a*';
} {1 2 3 4 5 6 7 8}

do_execsql_test 5.6 {
  INSERT INTO tt(tt) VALUES('integrity-check');
}

reset_db
do_execsql_test 5.7 {
  CREATE VIRTUAL TABLE tt USING fts5(content);
  INSERT INTO tt(tt, rank) VALUES('pgsz', 32);
  INSERT INTO tt VALUES('aa ab ac ad ae af');
}

do_execsql_test 5.8 {
  SELECT rowid FROM tt WHERE tt MATCH 'a*';
} {1}

finish_test

Changes to ext/fts5/test/fts5version.test.

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do_execsql_test 1.1 {
  CREATE VIRTUAL TABLE t1 USING fts5(one);
  INSERT INTO t1 VALUES('a b c d');
} {}

do_execsql_test 1.2 {
  SELECT * FROM t1_config WHERE k='version'
} {version 3}

do_execsql_test 1.3 {
  SELECT rowid FROM t1 WHERE t1 MATCH 'a';
} {1}

do_execsql_test 1.4 {
  UPDATE t1_config set v=4 WHERE k='version';
} 

do_test 1.5 {
  db close
  sqlite3 db test.db
  catchsql { SELECT * FROM t1 WHERE t1 MATCH 'a' }
} {1 {invalid fts5 file format (found 4, expected 3) - run 'rebuild'}}

do_test 1.6 {
  db close
  sqlite3 db test.db
  catchsql { INSERT INTO t1 VALUES('x y z') }
} {1 {invalid fts5 file format (found 4, expected 3) - run 'rebuild'}}

do_test 1.7 {
  execsql { DELETE FROM t1_config WHERE k='version' }
  db close
  sqlite3 db test.db
  catchsql { SELECT * FROM t1 WHERE t1 MATCH 'a' }
} {1 {invalid fts5 file format (found 0, expected 3) - run 'rebuild'}}


finish_test








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do_execsql_test 1.1 {
  CREATE VIRTUAL TABLE t1 USING fts5(one);
  INSERT INTO t1 VALUES('a b c d');
} {}

do_execsql_test 1.2 {
  SELECT * FROM t1_config WHERE k='version'
} {version 4}

do_execsql_test 1.3 {
  SELECT rowid FROM t1 WHERE t1 MATCH 'a';
} {1}

do_execsql_test 1.4 {
  UPDATE t1_config set v=5 WHERE k='version';
} 

do_test 1.5 {
  db close
  sqlite3 db test.db
  catchsql { SELECT * FROM t1 WHERE t1 MATCH 'a' }
} {1 {invalid fts5 file format (found 5, expected 4) - run 'rebuild'}}

do_test 1.6 {
  db close
  sqlite3 db test.db
  catchsql { INSERT INTO t1 VALUES('x y z') }
} {1 {invalid fts5 file format (found 5, expected 4) - run 'rebuild'}}

do_test 1.7 {
  execsql { DELETE FROM t1_config WHERE k='version' }
  db close
  sqlite3 db test.db
  catchsql { SELECT * FROM t1 WHERE t1 MATCH 'a' }
} {1 {invalid fts5 file format (found 0, expected 4) - run 'rebuild'}}


finish_test

Changes to ext/fts5/tool/loadfts5.tcl.

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  foreach f [glob -nocomplain -dir $dir *] {
    if {$::O(limit) && $::nRow>=$::O(limit)} break
    if {[file isdir $f]} {
      load_hierachy $f
    } else {
      db eval { INSERT INTO t1 VALUES($f, loadfile($f)) }
      incr ::nRow







      if {($::nRow % $::nRowPerDot)==0} {
        puts -nonewline .
        if {($::nRow % (65*$::nRowPerDot))==0} { puts "" }
        flush stdout
      }

................................................................................
  puts stderr "  -fts5        (use fts5)"
  puts stderr "  -porter      (use porter tokenizer)"
  puts stderr "  -delete      (delete the database file before starting)"
  puts stderr "  -limit N     (load no more than N documents)"
  puts stderr "  -automerge N (set the automerge parameter to N)"
  puts stderr "  -crisismerge N (set the crisismerge parameter to N)"
  puts stderr "  -prefix PREFIX (comma separated prefix= argument)"

  exit 1
}

set O(vtab)       fts5
set O(tok)        ""
set O(limit)      0
set O(delete)     0
set O(automerge)  -1
set O(crisismerge)  -1
set O(prefix)     ""


if {[llength $argv]<2} usage
set nOpt [expr {[llength $argv]-2}]
for {set i 0} {$i < $nOpt} {incr i} {
  set arg [lindex $argv $i]
  switch -- [lindex $argv $i] {
    -fts4 {
................................................................................
      set O(delete) 1
    }

    -limit {
      if { [incr i]>=$nOpt } usage
      set O(limit) [lindex $argv $i]
    }





    
    -automerge {
      if { [incr i]>=$nOpt } usage
      set O(automerge) [lindex $argv $i]
    }

    -crisismerge {
................................................................................
}

set dbfile [lindex $argv end-1]
if {$O(delete)} { file delete -force $dbfile }
sqlite3 db $dbfile
catch { load_static_extension db fts5 }
db func loadfile loadfile


db transaction {

  set pref ""
  if {$O(prefix)!=""} { set pref ", prefix='$O(prefix)'" }
  catch {
    db eval "CREATE VIRTUAL TABLE t1 USING $O(vtab) (path, content$O(tok)$pref)"
    db eval "INSERT INTO t1(t1, rank) VALUES('pgsz', 4050);"
  }
  if {$O(automerge)>=0} {
................................................................................
  if {$O(crisismerge)>=0} {
    if {$O(vtab) == "fts5"} {
      db eval {INSERT INTO t1(t1, rank) VALUES('crisismerge', $O(crisismerge))}
    } else {
    }
  }
  load_hierachy [lindex $argv end]
}










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  foreach f [glob -nocomplain -dir $dir *] {
    if {$::O(limit) && $::nRow>=$::O(limit)} break
    if {[file isdir $f]} {
      load_hierachy $f
    } else {
      db eval { INSERT INTO t1 VALUES($f, loadfile($f)) }
      incr ::nRow

      if {$::O(trans) && ($::nRow % $::O(trans))==0} {
        db eval { COMMIT }
        db eval { INSERT INTO t1(t1) VALUES('integrity-check') }
        db eval { BEGIN }
      }

      if {($::nRow % $::nRowPerDot)==0} {
        puts -nonewline .
        if {($::nRow % (65*$::nRowPerDot))==0} { puts "" }
        flush stdout
      }

................................................................................
  puts stderr "  -fts5        (use fts5)"
  puts stderr "  -porter      (use porter tokenizer)"
  puts stderr "  -delete      (delete the database file before starting)"
  puts stderr "  -limit N     (load no more than N documents)"
  puts stderr "  -automerge N (set the automerge parameter to N)"
  puts stderr "  -crisismerge N (set the crisismerge parameter to N)"
  puts stderr "  -prefix PREFIX (comma separated prefix= argument)"
  puts stderr "  -trans N     (commit after N inserts - 0 == never)"
  exit 1
}

set O(vtab)       fts5
set O(tok)        ""
set O(limit)      0
set O(delete)     0
set O(automerge)  -1
set O(crisismerge)  -1
set O(prefix)     ""
set O(trans)      0

if {[llength $argv]<2} usage
set nOpt [expr {[llength $argv]-2}]
for {set i 0} {$i < $nOpt} {incr i} {
  set arg [lindex $argv $i]
  switch -- [lindex $argv $i] {
    -fts4 {
................................................................................
      set O(delete) 1
    }

    -limit {
      if { [incr i]>=$nOpt } usage
      set O(limit) [lindex $argv $i]
    }

    -trans {
      if { [incr i]>=$nOpt } usage
      set O(trans) [lindex $argv $i]
    }
    
    -automerge {
      if { [incr i]>=$nOpt } usage
      set O(automerge) [lindex $argv $i]
    }

    -crisismerge {
................................................................................
}

set dbfile [lindex $argv end-1]
if {$O(delete)} { file delete -force $dbfile }
sqlite3 db $dbfile
catch { load_static_extension db fts5 }
db func loadfile loadfile
db eval "PRAGMA page_size=4096"


db eval BEGIN
  set pref ""
  if {$O(prefix)!=""} { set pref ", prefix='$O(prefix)'" }
  catch {
    db eval "CREATE VIRTUAL TABLE t1 USING $O(vtab) (path, content$O(tok)$pref)"
    db eval "INSERT INTO t1(t1, rank) VALUES('pgsz', 4050);"
  }
  if {$O(automerge)>=0} {
................................................................................
  if {$O(crisismerge)>=0} {
    if {$O(vtab) == "fts5"} {
      db eval {INSERT INTO t1(t1, rank) VALUES('crisismerge', $O(crisismerge))}
    } else {
    }
  }
  load_hierachy [lindex $argv end]
db eval COMMIT