SQLite

  /* Only a BTREE_SINGLE database can be BTREE_UNORDERED */
  assert( (flags & BTREE_UNORDERED)==0 || (flags & BTREE_SINGLE)!=0 );

  /* A BTREE_SINGLE database is always a temporary and/or ephemeral */
  assert( (flags & BTREE_SINGLE)==0 || isTempDb );











  if( db->flags & SQLITE_NoReadlock ){
    flags |= BTREE_NO_READLOCK;
  }
  if( isMemdb ){
    flags |= BTREE_MEMORY;

  }
  if( (vfsFlags & SQLITE_OPEN_MAIN_DB)!=0 && (isMemdb || isTempDb) ){
    vfsFlags = (vfsFlags & ~SQLITE_OPEN_MAIN_DB) | SQLITE_OPEN_TEMP_DB;
  }
  p = sqlite3MallocZero(sizeof(Btree));
  if( !p ){
    return SQLITE_NOMEM;

** pager.h.
*/
#define BTREE_OMIT_JOURNAL  1  /* Do not create or use a rollback journal */
#define BTREE_NO_READLOCK   2  /* Omit readlocks on readonly files */
#define BTREE_MEMORY        4  /* This is an in-memory DB */
#define BTREE_SINGLE        8  /* The file contains at most 1 b-tree */
#define BTREE_UNORDERED    16  /* Use of a hash implementation is OK */


int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetSafetyLevel(Btree*,int,int,int);
int sqlite3BtreeSyncDisabled(Btree*);
int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
int sqlite3BtreeGetPageSize(Btree*);

*/
static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
  Table *pTab = pIndex->pTable;  /* The table that is indexed */
  int iTab = pParse->nTab++;     /* Btree cursor used for pTab */
  int iIdx = pParse->nTab++;     /* Btree cursor used for pIndex */
  int iSorter = iTab;            /* Cursor opened by OpenSorter (if in use) */
  int addr1;                     /* Address of top of loop */
  int addr2;                     /* Address to jump to for next iteration */
  int tnum;                      /* Root page of index */
  Vdbe *v;                       /* Generate code into this virtual machine */
  KeyInfo *pKey;                 /* KeyInfo for index */
  int regIdxKey;                 /* Registers containing the index key */
  int regRecord;                 /* Register holding assemblied index record */
  sqlite3 *db = pParse->db;      /* The database connection */
  int iDb = sqlite3SchemaToIndex(db, pIndex->pSchema);

    sqlite3VdbeChangeP5(v, 1);
  }

  /* Open the sorter cursor if we are to use one. */
  if( bUseSorter ){
    iSorter = pParse->nTab++;
    sqlite3VdbeAddOp4(v, OP_OpenSorter, iSorter, 0, 0, (char*)pKey, P4_KEYINFO);

  }

  /* Open the table. Loop through all rows of the table, inserting index
  ** records into the sorter. */
  sqlite3OpenTable(pParse, iTab, iDb, pTab, OP_OpenRead);
  addr1 = sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
  addr2 = addr1 + 1;
  regRecord = sqlite3GetTempReg(pParse);
  regIdxKey = sqlite3GenerateIndexKey(pParse, pIndex, iTab, regRecord, 1);

  if( bUseSorter ){
    sqlite3VdbeAddOp2(v, OP_SorterInsert, iSorter, regRecord);
    sqlite3VdbeAddOp2(v, OP_Next, iTab, addr1+1);
    sqlite3VdbeJumpHere(v, addr1);
    addr1 = sqlite3VdbeAddOp2(v, OP_SorterSort, iSorter, 0);
    if( pIndex->onError!=OE_None ){
      int j2 = sqlite3VdbeCurrentAddr(v) + 3;
      sqlite3VdbeAddOp2(v, OP_Goto, 0, j2);
      addr2 = sqlite3VdbeCurrentAddr(v);
      sqlite3VdbeAddOp3(v, OP_SorterCompare, iSorter, j2, regRecord);
      sqlite3HaltConstraint(
          pParse, OE_Abort, "indexed columns are not unique", P4_STATIC
      );
    }else{
      addr2 = sqlite3VdbeCurrentAddr(v);
    }
    sqlite3VdbeAddOp2(v, OP_SorterData, iSorter, regRecord);
  }else if( pIndex->onError!=OE_None ){
    const int regRowid = regIdxKey + pIndex->nColumn;
    const int j2 = sqlite3VdbeCurrentAddr(v) + 2;
    void * const pRegKey = SQLITE_INT_TO_PTR(regIdxKey);

    /* The registers accessed by the OP_IsUnique opcode were allocated
    ** using sqlite3GetTempRange() inside of the sqlite3GenerateIndexKey()
    ** call above. Just before that function was freed they were released
    ** (made available to the compiler for reuse) using 
    ** sqlite3ReleaseTempRange(). So in some ways having the OP_IsUnique
    ** opcode use the values stored within seems dangerous. However, since
    ** we can be sure that no other temp registers have been allocated
    ** since sqlite3ReleaseTempRange() was called, it is safe to do so.
    */
    sqlite3VdbeAddOp4(v, OP_IsUnique, iIdx, j2, regRowid, pRegKey, P4_INT32);
    sqlite3HaltConstraint(
        pParse, OE_Abort, "indexed columns are not unique", P4_STATIC);
  }
  sqlite3VdbeAddOp3(v, OP_IdxInsert, iIdx, regRecord, bUseSorter);
  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
  sqlite3ReleaseTempReg(pParse, regRecord);
  sqlite3VdbeAddOp2(v, bUseSorter ? OP_SorterNext : OP_Next, iSorter, addr2);
  sqlite3VdbeJumpHere(v, addr1);

  sqlite3VdbeAddOp1(v, OP_Close, iTab);
  sqlite3VdbeAddOp1(v, OP_Close, iIdx);
  sqlite3VdbeAddOp1(v, OP_Close, iSorter);
}

      AggInfo *pAggInfo = pExpr->pAggInfo;
      struct AggInfo_col *pCol = &pAggInfo->aCol[pExpr->iAgg];
      if( !pAggInfo->directMode ){
        assert( pCol->iMem>0 );
        inReg = pCol->iMem;
        break;
      }else if( pAggInfo->useSortingIdx ){
        sqlite3VdbeAddOp3(v, OP_Column, pAggInfo->sortingIdxPTab,
                              pCol->iSorterColumn, target);
        break;
      }
      /* Otherwise, fall thru into the TK_COLUMN case */
    }
    case TK_COLUMN: {
      if( pExpr->iTable<0 ){

        }
        regRecord = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
        sqlite3VdbeAddOp2(v, OP_SorterInsert, sAggInfo.sortingIdx, regRecord);
        sqlite3ReleaseTempReg(pParse, regRecord);
        sqlite3ReleaseTempRange(pParse, regBase, nCol);
        sqlite3WhereEnd(pWInfo);
        sAggInfo.sortingIdxPTab = sortPTab = pParse->nTab++;
        sortOut = sqlite3GetTempReg(pParse);
        sqlite3VdbeAddOp3(v, OP_OpenPseudo, sortPTab, sortOut, nCol);
        sqlite3VdbeAddOp2(v, OP_SorterSort, sAggInfo.sortingIdx, addrEnd);
        VdbeComment((v, "GROUP BY sort"));
        sAggInfo.useSortingIdx = 1;
        sqlite3ExprCacheClear(pParse);
      }

*/
struct AggInfo {
  u8 directMode;          /* Direct rendering mode means take data directly
                          ** from source tables rather than from accumulators */
  u8 useSortingIdx;       /* In direct mode, reference the sorting index rather
                          ** than the source table */
  int sortingIdx;         /* Cursor number of the sorting index */
  int sortingIdxPTab;     /* Cursor number of pseudo-table */
  ExprList *pGroupBy;     /* The group by clause */
  int nSortingColumn;     /* Number of columns in the sorting index */
  struct AggInfo_col {    /* For each column used in source tables */
    Table *pTab;             /* Source table */
    int iTable;              /* Cursor number of the source table */
    int iColumn;             /* Column number within the source table */
    int iSorterColumn;       /* Column number in the sorting index */

/* Opcode: OpenAutoindex P1 P2 * P4 *
**
** This opcode works the same as OP_OpenEphemeral.  It has a
** different name to distinguish its use.  Tables created using
** by this opcode will be used for automatically created transient
** indices in joins.
*/







case OP_OpenAutoindex: 

case OP_OpenEphemeral: {
  VdbeCursor *pCx;
  static const int vfsFlags = 
      SQLITE_OPEN_READWRITE |
      SQLITE_OPEN_CREATE |
      SQLITE_OPEN_EXCLUSIVE |
      SQLITE_OPEN_DELETEONCLOSE |
      SQLITE_OPEN_TRANSIENT_DB;

  assert( pOp->p1>=0 );

  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBt, 
                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);
  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeBeginTrans(pCx->pBt, 1);

    }else{
      rc = sqlite3BtreeCursor(pCx->pBt, MASTER_ROOT, 1, 0, pCx->pCursor);
      pCx->isTable = 1;
    }
  }
  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
  pCx->isIndex = !pCx->isTable;
  break;
}

/* Opcode: OpenSorter P1 P2 * P4 *
**
** This opcode works like OP_OpenEphemeral except that it opens
** a transient index that is specifically designed to sort large
** tables using an external merge-sort algorithm.
*/
case OP_SorterOpen:

case OP_OpenSorter: {
  VdbeCursor *pCx;
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, 1);
  if( pCx==0 ) goto no_mem;
  pCx->pKeyInfo = pOp->p4.pKeyInfo;
  pCx->pKeyInfo->enc = ENC(p->db);
  pCx->isSorter = 1;
  rc = sqlite3VdbeSorterInit(db, pCx);


  break;
}

/* Opcode: OpenPseudo P1 P2 P3 * *
**
** Open a new cursor that points to a fake table that contains a single
** row of data.  The content of that one row in the content of memory

** This is used by trigger programs.
*/
case OP_ResetCount: {
  sqlite3VdbeSetChanges(db, p->nChange);
  p->nChange = 0;
  break;
}

/* Opcode: SorterCompare P1 P2 P3
**
** P1 is a sorter cursor. This instruction compares the record blob in 
** register P3 with the entry that the sorter cursor currently points to.
** If, excluding the rowid fields at the end, the two records are a match,
** fall through to the next instruction. Otherwise, jump to instruction P2.
*/
case OP_SorterCompare: {
  VdbeCursor *pC;
  int res;

  pC = p->apCsr[pOp->p1];
  assert( isSorter(pC) );
  pIn3 = &aMem[pOp->p3];
  rc = sqlite3VdbeSorterCompare(pC, pIn3, &res);
  if( res ){
    pc = pOp->p2-1;
  }
  break;
};

/* Opcode: SorterData P1 P2 * * *
**
** Write into register P2 the current sorter data for sorter cursor P1.
*/
case OP_SorterData: {
  VdbeCursor *pC;
  pOut = &aMem[pOp->p2];
  pC = p->apCsr[pOp->p1];
  assert( pC->isSorter );
  rc = sqlite3VdbeSorterRowkey(pC, pOut);
  break;
}

/* Opcode: RowData P1 P2 * * *
**
** Write into register P2 the complete row data for cursor P1.
** There is no interpretation of the data.  
** It is just copied onto the P2 register exactly as 
** it is found in the database file.

** There is no interpretation of the data.  
** The key is copied onto the P3 register exactly as 
** it is found in the database file.
**
** If the P1 cursor must be pointing to a valid row (not a NULL row)
** of a real table, not a pseudo-table.
*/

case OP_RowKey:
case OP_RowData: {
  VdbeCursor *pC;
  BtCursor *pCrsr;
  u32 n;
  i64 n64;

  pOut = &aMem[pOp->p2];
  memAboutToChange(p, pOut);

  /* Note that RowKey and RowData are really exactly the same instruction */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC->isSorter==0 );
  assert( pC->isTable || pOp->opcode!=OP_RowData );
  assert( pC->isIndex || pOp->opcode==OP_RowData );
  assert( pC!=0 );
  assert( pC->nullRow==0 );
  assert( pC->pseudoTableReg==0 );
  assert( pC->isSorter==(pOp->opcode==OP_SorterData) );







  assert( pC->pCursor!=0 );
  pCrsr = pC->pCursor;
  assert( sqlite3BtreeCursorIsValid(pCrsr) );

  /* The OP_RowKey and OP_RowData opcodes always follow OP_NotExists or
  ** OP_Rewind/Op_Next with no intervening instructions that might invalidate
  ** the cursor.  Hence the following sqlite3VdbeCursorMoveto() call is always

  assert( pOp->p5<=ArraySize(p->aCounter) );
  pC = p->apCsr[pOp->p1];
  if( pC==0 ){
    break;  /* See ticket #2273 */
  }
  assert( pC->isSorter==(pOp->opcode==OP_SorterNext) );
  if( isSorter(pC) ){
    assert( pOp->opcode==OP_SorterNext );
    rc = sqlite3VdbeSorterNext(db, pC, &res);
  }else{
    res = 1;
    assert( pC->deferredMoveto==0 );
    assert( pC->pCursor );
    assert( pOp->opcode!=OP_Next || pOp->p4.xAdvance==sqlite3BtreeNext );
    assert( pOp->opcode!=OP_Prev || pOp->p4.xAdvance==sqlite3BtreePrevious );

  pIn2 = &aMem[pOp->p2];
  assert( pIn2->flags & MEM_Blob );
  pCrsr = pC->pCursor;
  if( ALWAYS(pCrsr!=0) ){
    assert( pC->isTable==0 );
    rc = ExpandBlob(pIn2);
    if( rc==SQLITE_OK ){
      if( isSorter(pC) ){
        rc = sqlite3VdbeSorterWrite(db, pC, pIn2);
      }else{
        nKey = pIn2->n;
        zKey = pIn2->z;


        rc = sqlite3BtreeInsert(pCrsr, zKey, nKey, "", 0, 0, pOp->p3, 
            ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0)
            );
        assert( pC->deferredMoveto==0 );

        pC->cacheStatus = CACHE_STALE;
      }
    }
  }
  break;
}

/* Opcode: IdxDelete P1 P2 P3 * *
**

#ifdef SQLITE_OMIT_MERGE_SORT
# define sqlite3VdbeSorterInit(Y,Z)      SQLITE_OK
# define sqlite3VdbeSorterWrite(X,Y,Z)   SQLITE_OK
# define sqlite3VdbeSorterClose(Y,Z)
# define sqlite3VdbeSorterRowkey(Y,Z)    SQLITE_OK
# define sqlite3VdbeSorterRewind(X,Y,Z)  SQLITE_OK
# define sqlite3VdbeSorterNext(X,Y,Z)    SQLITE_OK
# define sqlite3VdbeSorterCompare(X,Y,Z) SQLITE_OK
#else
int sqlite3VdbeSorterInit(sqlite3 *, VdbeCursor *);

void sqlite3VdbeSorterClose(sqlite3 *, VdbeCursor *);
int sqlite3VdbeSorterRowkey(VdbeCursor *, Mem *);
int sqlite3VdbeSorterNext(sqlite3 *, VdbeCursor *, int *);
int sqlite3VdbeSorterRewind(sqlite3 *, VdbeCursor *, int *);
int sqlite3VdbeSorterWrite(sqlite3 *, VdbeCursor *, Mem *);
int sqlite3VdbeSorterCompare(VdbeCursor *, Mem *, int *);
#endif

#if !defined(SQLITE_OMIT_SHARED_CACHE) && SQLITE_THREADSAFE>0
  void sqlite3VdbeEnter(Vdbe*);
  void sqlite3VdbeLeave(Vdbe*);
#else
# define sqlite3VdbeEnter(X)

#include "sqliteInt.h"
#include "vdbeInt.h"

#ifndef SQLITE_OMIT_MERGE_SORT

typedef struct VdbeSorterIter VdbeSorterIter;
typedef struct SorterRecord SorterRecord;

/*
** NOTES ON DATA STRUCTURE USED FOR N-WAY MERGES:
**
** As keys are added to the sorter, they are written to disk in a series
** of sorted packed-memory-arrays (PMAs). The size of each PMA is roughly
** the same as the cache-size allowed for temporary databases. In order

**     aTree[] = { X, 0   0, 6    0, 3, 5, 6 }
**
** In other words, each time we advance to the next sorter element, log2(N)
** key comparison operations are required, where N is the number of segments
** being merged (rounded up to the next power of 2).
*/
struct VdbeSorter {

  int nInMemory;                  /* Current size of b-tree contents as PMA */
  int nTree;                      /* Used size of aTree/aIter (power of 2) */
  VdbeSorterIter *aIter;          /* Array of iterators to merge */
  int *aTree;                     /* Current state of incremental merge */
  i64 iWriteOff;                  /* Current write offset within file pTemp1 */
  i64 iReadOff;                   /* Current read offset within file pTemp1 */
  sqlite3_file *pTemp1;           /* PMA file 1 */
  int nPMA;                       /* Number of PMAs stored in pTemp1 */
  SorterRecord *pRecord;          /* Head of in-memory record list */
  int nLimit1;                    /* Minimum PMA size, in bytes */
  int nLimit2;                    /* Maximum PMA size, in bytes */
};

/*
** The following type is an iterator for a PMA. It caches the current key in 
** variables nKey/aKey. If the iterator is at EOF, pFile==0.
*/
struct VdbeSorterIter {
  i64 iReadOff;                   /* Current read offset */
  i64 iEof;                       /* 1 byte past EOF for this iterator */
  sqlite3_file *pFile;            /* File iterator is reading from */
  int nAlloc;                     /* Bytes of space at aAlloc */
  u8 *aAlloc;                     /* Allocated space */
  int nKey;                       /* Number of bytes in key */
  u8 *aKey;                       /* Pointer to current key */
};

/*
** A structure to store a single record. All in-memory records are connected
** together into a linked list headed at VdbeSorter.pRecord using the 
** SorterRecord.pNext pointer.
*/
struct SorterRecord {
  void *pVal;
  int nVal;
  SorterRecord *pNext;
};

/* Minimum allowable value for the VdbeSorter.nWorking variable */
#define SORTER_MIN_WORKING 10

/* Maximum number of segments to merge in a single pass. */
#define SORTER_MAX_MERGE_COUNT 16

  }
  if( rc==SQLITE_OK ){
    rc = vdbeSorterIterNext(db, pIter);
  }
  return rc;
}


/*
** Compare key1 (buffer pKey1, size nKey1 bytes) with key2 (buffer pKey2, 
** size nKey2 bytes).  Argument pKeyInfo supplies the collation functions
** used by the comparison. If an error occurs, return an SQLite error code.
** Otherwise, return SQLITE_OK and set *pRes to a negative, zero or positive
** value, depending on whether key1 is smaller, equal to or larger than key2.
**
** If the bOmitRowid argument is non-zero, assume both keys end in a rowid
** field. For the purposes of the comparison, ignore it. Also, if bOmitRowid
** is true and key1 contains even a single NULL value, it is considered to
** be less than key2. Even if key2 also contains NULL values.
*/
static int vdbeSorterCompare(
  KeyInfo *pKeyInfo,              /* Collation functions to use in comparison */
  int bOmitRowid,                 /* Ignore rowid field at end of keys */
  void *pKey1, int nKey1,         /* Left side of comparison */
  void *pKey2, int nKey2,         /* Right side of comparison */
  int *pRes                       /* OUT: Result of comparison */
){
  char aSpace[150];
  UnpackedRecord *r2;
  int i;

  r2 = sqlite3VdbeRecordUnpack(pKeyInfo, nKey2, pKey2, aSpace, sizeof(aSpace));
  if( r2==0 ) return SQLITE_NOMEM;
  if( bOmitRowid ){
    for(i=0; i<r2->nField-1; i++){
      if( r2->aMem[i].flags & MEM_Null ){
        *pRes = -1;
        sqlite3VdbeDeleteUnpackedRecord(r2);
        return SQLITE_OK;
      }
    }
    r2->flags |= UNPACKED_PREFIX_MATCH;
    r2->nField--;
    assert( r2->nField>0 );
  }

  *pRes = sqlite3VdbeRecordCompare(nKey1, pKey1, r2);
  sqlite3VdbeDeleteUnpackedRecord(r2);
  return SQLITE_OK;
}

/*
** This function is called to compare two iterator keys when merging 
** multiple b-tree segments. Parameter iOut is the index of the aTree[] 
** value to recalculate.
*/
static int vdbeSorterDoCompare(VdbeCursor *pCsr, int iOut){
  VdbeSorter *pSorter = pCsr->pSorter;

  p2 = &pSorter->aIter[i2];

  if( p1->pFile==0 ){
    iRes = i2;
  }else if( p2->pFile==0 ){
    iRes = i1;
  }else{


    int res;
    int rc = vdbeSorterCompare(
        pCsr->pKeyInfo, 0, p1->aKey, p1->nKey, p2->aKey, p2->nKey, &res
    );
    if( rc!=SQLITE_OK ) return rc;
    if( res<=0 ){

      iRes = i1;
    }else{
      iRes = i2;
    }

  }

  pSorter->aTree[iOut] = iRes;
  return SQLITE_OK;
}

/*
** Initialize the temporary index cursor just opened as a sorter cursor.
*/
int sqlite3VdbeSorterInit(sqlite3 *db, VdbeCursor *pCsr){
  int pgsz;                       /* Page size of main database */

  assert( pCsr->pKeyInfo && pCsr->pBt==0 );
  pCsr->pSorter = sqlite3DbMallocZero(db, sizeof(VdbeSorter));
  if( pCsr->pSorter==0 ){
    return SQLITE_NOMEM;
  }

  pgsz = sqlite3BtreeGetPageSize(db->aDb[0].pBt);
  pCsr->pSorter->nLimit1 = 10 * pgsz;
  pCsr->pSorter->nLimit2 = db->aDb[0].pSchema->cache_size * pgsz;

  return SQLITE_OK;
}

/*
** Free the list of sorted records starting at pRecord.
*/
static void vdbeSorterRecordFree(sqlite3 *db, SorterRecord *pRecord){
  SorterRecord *p;
  SorterRecord *pNext;
  for(p=pRecord; p; p=pNext){
    pNext = p->pNext;
    sqlite3DbFree(db, p->pVal);
    sqlite3DbFree(db, p);
  }
}

/*
** Free any cursor components allocated by sqlite3VdbeSorterXXX routines.
*/
void sqlite3VdbeSorterClose(sqlite3 *db, VdbeCursor *pCsr){
  VdbeSorter *pSorter = pCsr->pSorter;
  if( pSorter ){
    if( pSorter->aIter ){
      int i;
      for(i=0; i<pSorter->nTree; i++){
        vdbeSorterIterZero(db, &pSorter->aIter[i]);
      }
      sqlite3DbFree(db, pSorter->aIter);
    }
    if( pSorter->pTemp1 ){
      sqlite3OsCloseFree(pSorter->pTemp1);
    }
    vdbeSorterRecordFree(db, pSorter->pRecord);
    sqlite3DbFree(db, pSorter);
    pCsr->pSorter = 0;
  }
}

/*
** Allocate space for a file-handle and open a temporary file. If successful,
** set *ppFile to point to the malloc'd file-handle and return SQLITE_OK.
** Otherwise, set *ppFile to 0 and return an SQLite error code.
*/
static int vdbeSorterOpenTempFile(sqlite3 *db, sqlite3_file **ppFile){
  int dummy;
  return sqlite3OsOpenMalloc(db->pVfs, 0, ppFile,
      SQLITE_OPEN_TEMP_JOURNAL |
      SQLITE_OPEN_READWRITE    | SQLITE_OPEN_CREATE |
      SQLITE_OPEN_EXCLUSIVE    | SQLITE_OPEN_DELETEONCLOSE, &dummy
  );
}

/*
** Attemp to merge the two sorted lists p1 and p2 into a single list. If no
** error occurs set *ppOut to the head of the new list and return SQLITE_OK.
*/
static int vdbeSorterMerge(
  sqlite3 *db,                    /* Database handle */
  KeyInfo *pKeyInfo,              /* Collation functions to use in comparison */
  SorterRecord *p1,               /* First list to merge */
  SorterRecord *p2,               /* Second list to merge */
  SorterRecord **ppOut            /* OUT: Head of merged list */
){
  int rc = SQLITE_OK;
  SorterRecord *pFinal = 0;
  SorterRecord **pp = &pFinal;

  while( p1 || p2 ){
    if( p1==0 ){
      *pp = p2;
      p2 = 0;
    }else if( p2==0 ){
      *pp = p1;
      p1 = 0;
    }else{
      int res;
      rc = vdbeSorterCompare(
          pKeyInfo, 0, p1->pVal, p1->nVal, p2->pVal, p2->nVal, &res
      );
      if( rc!=SQLITE_OK ){
        vdbeSorterRecordFree(db, p1);
        vdbeSorterRecordFree(db, p2);
        vdbeSorterRecordFree(db, pFinal);
        pFinal = 0;
        break;
      }
      if( res<=0 ){
        *pp = p1;
        pp = &p1->pNext;
        p1 = p1->pNext;
      }else{
        *pp = p2;
        pp = &p2->pNext;
        p2 = p2->pNext;
      }
      *pp = 0;
    }
  }

  *ppOut = pFinal;
  return rc;
}

/*
** Sort the linked list of records headed at pCsr->pRecord. Return SQLITE_OK
** if successful, or an SQLite error code (i.e. SQLITE_NOMEM) if an error
** occurs.
*/
static int vdbeSorterSort(sqlite3 *db, VdbeCursor *pCsr){
  int rc = SQLITE_OK;
  int i;
  SorterRecord **aSlot;
  SorterRecord *p;
  VdbeSorter *pSorter = pCsr->pSorter;
  KeyInfo *pKeyInfo = pCsr->pKeyInfo;

  aSlot = (SorterRecord **)sqlite3MallocZero(64 * sizeof(SorterRecord *));
  if( !aSlot ){
    return SQLITE_NOMEM;
  }

  p = pSorter->pRecord;
  while( p ){
    SorterRecord *pNext = p->pNext;
    p->pNext = 0;
    for(i=0; rc==SQLITE_OK && aSlot[i]; i++){
      rc = vdbeSorterMerge(db, pKeyInfo, p, aSlot[i], &p);
      aSlot[i] = 0;
    }
    if( rc!=SQLITE_OK ){
      vdbeSorterRecordFree(db, pNext);
      break;
    }
    aSlot[i] = p;
    p = pNext;
  }

  p = 0;
  for(i=0; i<64; i++){
    if( rc==SQLITE_OK ){
      rc = vdbeSorterMerge(db, pKeyInfo, p, aSlot[i], &p);
    }else{
      vdbeSorterRecordFree(db, aSlot[i]);
    }
  }
  pSorter->pRecord = p;

#if 0
  {
    SorterRecord *pTmp1 = 0;
    SorterRecord *pTmp2;
    for(pTmp2=pSorter->pRecord; pTmp2 && rc==SQLITE_OK; pTmp2=pTmp2->pNext){
      if( pTmp1 ){
        int res;
        rc = vdbeSorterCompare(pKeyInfo, 
            0, pTmp1->pVal, pTmp1->nVal, pTmp2->pVal, pTmp2->nVal, &res
        );
        assert( rc!=SQLITE_OK || res<0 );
      }
      pTmp1 = pTmp2;
    }
  }
#endif

  if( rc!=SQLITE_OK ){
  }
  sqlite3_free(aSlot);
  return rc;
}


/*
** Write the current contents of the in-memory linked-list to a PMA. Return
** SQLITE_OK if successful, or an SQLite error code otherwise.
**
** The format of a PMA is:
**
**     * A varint. This varint contains the total number of bytes of content
**       in the PMA (not including the varint itself).
**
**     * One or more records packed end-to-end in order of ascending keys. 
**       Each record consists of a varint followed by a blob of data (the 
**       key). The varint is the number of bytes in the blob of data.
*/
static int vdbeSorterListToPMA(sqlite3 *db, VdbeCursor *pCsr){
  int rc = SQLITE_OK;             /* Return code */
  VdbeSorter *pSorter = pCsr->pSorter;



  if( pSorter->nInMemory==0 ){


    assert( pSorter->pRecord==0 );
    return rc;
  }

  rc = vdbeSorterSort(db, pCsr);

  /* If the first temporary PMA file has not been opened, open it now. */
  if( rc==SQLITE_OK && pSorter->pTemp1==0 ){
    rc = vdbeSorterOpenTempFile(db, &pSorter->pTemp1);
    assert( rc!=SQLITE_OK || pSorter->pTemp1 );
    assert( pSorter->iWriteOff==0 );
    assert( pSorter->nPMA==0 );
  }

  if( rc==SQLITE_OK ){
    i64 iOff = pSorter->iWriteOff;
    SorterRecord *p;
    SorterRecord *pNext = 0;

    pSorter->nPMA++;

    rc = vdbeSorterWriteVarint(pSorter->pTemp1, pSorter->nInMemory, &iOff);
    for(p=pSorter->pRecord; rc==SQLITE_OK && p; p=pNext){



      pNext = p->pNext;


      rc = vdbeSorterWriteVarint(pSorter->pTemp1, p->nVal, &iOff);












      if( rc==SQLITE_OK ){



        rc = sqlite3OsWrite(pSorter->pTemp1, p->pVal, p->nVal, iOff);
        iOff += p->nVal;
      }

      sqlite3DbFree(db, p->pVal);

      sqlite3DbFree(db, p);
    }

    /* This assert verifies that unless an error has occurred, the size of 
    ** the PMA on disk is the same as the expected size stored in
    ** pSorter->nInMemory. */ 
    assert( rc!=SQLITE_OK || pSorter->nInMemory==(
          iOff-pSorter->iWriteOff-sqlite3VarintLen(pSorter->nInMemory)
    ));

    pSorter->iWriteOff = iOff;
    pSorter->pRecord = p;
  }


  return rc;
}

/*
** Add a record to the sorter.










*/
int sqlite3VdbeSorterWrite(
  sqlite3 *db,                    /* Database handle */
  VdbeCursor *pCsr,               /* Sorter cursor */
  Mem *pVal                       /* Memory cell containing record */
){
  VdbeSorter *pSorter = pCsr->pSorter;



  int rc;
  SorterRecord *pNew;




  assert( pSorter );
  pSorter->nInMemory += sqlite3VarintLen(pVal->n) + pVal->n;




  pNew = (SorterRecord *)sqlite3DbMallocZero(db, sizeof(SorterRecord));
  if( pNew==0 ){
    rc = SQLITE_NOMEM;
  }else{
    rc = sqlite3VdbeMemMakeWriteable(pVal);
    if( rc==SQLITE_OK ){
      pNew->pVal = pVal->z;
      pNew->nVal = pVal->n;
      pVal->zMalloc = 0;
      sqlite3VdbeMemSetNull(pVal);
      pNew->pNext = pSorter->pRecord;
      pSorter->pRecord = pNew;
    }else{
      sqlite3DbFree(db, pNew);
      rc = SQLITE_NOMEM;
    }
  }












  /* See if the contents of the sorter should now be written out. They
  ** are written out when either of the following are true:

  **
  **   * The total memory allocated for the in-memory list is greater 
  **     than (page-size * cache-size), or
  **
  **   * The total memory allocated for the in-memory list is greater 
  **     than (page-size * 10) and sqlite3HeapNearlyFull() returns true.



  */
  if( rc==SQLITE_OK && (
        (pSorter->nInMemory>pSorter->nLimit2)
     || (pSorter->nInMemory>pSorter->nLimit1 && sqlite3HeapNearlyFull())


  )){
    rc = vdbeSorterListToPMA(db, pCsr);
    pSorter->nInMemory = 0;
  }




  return rc;
}

/*
** Helper function for sqlite3VdbeSorterRewind(). 
*/
static int vdbeSorterInitMerge(

  int nIter;                      /* Number of iterators used */
  int nByte;                      /* Bytes of space required for aIter/aTree */
  int N = 2;                      /* Power of 2 >= nIter */

  assert( pSorter );

  /* Write the current b-tree to a PMA. Close the b-tree cursor. */
  rc = vdbeSorterListToPMA(db, pCsr);

  if( rc!=SQLITE_OK ) return rc;
  if( pSorter->nPMA==0 ){
    *pbEof = 1;
    return SQLITE_OK;
  }

  /* Allocate space for aIter[] and aTree[]. */

** Copy the current sorter key into the memory cell pOut.
*/
int sqlite3VdbeSorterRowkey(VdbeCursor *pCsr, Mem *pOut){
  VdbeSorter *pSorter = pCsr->pSorter;
  VdbeSorterIter *pIter;

  pIter = &pSorter->aIter[ pSorter->aTree[1] ];







  if( sqlite3VdbeMemGrow(pOut, pIter->nKey, 0) ){
    return SQLITE_NOMEM;
  }
  pOut->n = pIter->nKey;
  MemSetTypeFlag(pOut, MEM_Blob);
  memcpy(pOut->z, pIter->aKey, pIter->nKey);

  return SQLITE_OK;
}

/*
** Compare the key in memory cell pVal with the key that the sorter cursor
** passed as the first argument currently points to. For the purposes of
** the comparison, ignore the rowid field at the end of each record.
**
** If an error occurs, return an SQLite error code (i.e. SQLITE_NOMEM).
** Otherwise, set *pRes to a negative, zero or positive value if the
** key in pVal is smaller than, equal to or larger than the current sorter
** key.
*/
int sqlite3VdbeSorterCompare(
  VdbeCursor *pCsr,               /* Sorter cursor */
  Mem *pVal,                      /* Value to compare to current sorter key */
  int *pRes                       /* OUT: Result of comparison */
){
  int rc;
  VdbeSorter *pSorter = pCsr->pSorter;
  VdbeSorterIter *pIter;
  pIter = &pSorter->aIter[ pSorter->aTree[1] ];
  rc = vdbeSorterCompare(pCsr->pKeyInfo, 1,
      pVal->z, pVal->n, pIter->aKey, pIter->nKey, pRes
  );
  assert( rc!=SQLITE_OK || *pRes<=0 );
  return rc;
}

#endif /* #ifndef SQLITE_OMIT_MERGE_SORT */

    DROP TABLE t1;
    CREATE TABLE t1(x);
  COMMIT;
  CREATE INDEX i1 ON t1(x); 
  PRAGMA integrity_check
} {ok}

do_execsql_test 2.1 {
  BEGIN;
    CREATE TABLE t2(x);
    INSERT INTO t2 VALUES(14);
    INSERT INTO t2 VALUES(35);
    INSERT INTO t2 VALUES(15);
    INSERT INTO t2 VALUES(35);
    INSERT INTO t2 VALUES(16);
  COMMIT;
}
do_catchsql_test 2.2 {
  CREATE UNIQUE INDEX i3 ON t2(x);
} {1 {indexed columns are not unique}}


finish_test