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Overview
Comment:Delta-encode terms in interior nodes. While experiments have shown that this is of marginal utility when encoding terms resulting from regular English text, it turns out to be very useful when encoding inputs with very large terms. (CVS 3520)
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SHA1:c8151a998ec2423b417566823dc9957c7d5d782c
User & Date: shess 2006-11-29 01:02:03
Context
2006-11-29
05:17
http://www.sqlite.org/cvstrac/tktview?tn=2046

The virtual table interface allows for a cursor to field multiple xFilter() calls. For instance, if a join is done with a virtual table, there could be a call for each row which potentially matches. Unfortunately, fulltextFilter() assumes that it has a fresh cursor, and overwrites a prepared statement and a malloc'ed pointer, resulting in unfinalized statements and a memory leak.

This change hacks the code to manually clean up offending items in fulltextFilter(), emphasis on "hacks", since it's a fragile fix insofar as future additions to fulltext_cursor could continue to have the problem. (CVS 3521) check-in: 18142fdb user: shess tags: trunk

01:02
Delta-encode terms in interior nodes. While experiments have shown that this is of marginal utility when encoding terms resulting from regular English text, it turns out to be very useful when encoding inputs with very large terms. (CVS 3520) check-in: c8151a99 user: shess tags: trunk
2006-11-23
21:09
Improvements to the speed tests recently added to the test suite. (CVS 3519) check-in: 272c1a6e user: drh tags: trunk
Changes
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Changes to ext/fts2/fts2.c.

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** InteriorReader.  InteriorWriters are created as needed when
** SegmentWriter creates new leaf nodes, or when an interior node
** itself grows too big and must be split.  The format of interior
** nodes:
**
** varint iHeight;           (height from leaf level, always >0)
** varint iBlockid;          (block id of node's leftmost subtree)
** array {
**   varint nTerm;           (length of term)
**   char pTerm[nTerm];      (content of term)






** }
**

** Here, array { X } means zero or more occurrences of X, adjacent in
** memory.
**
** An interior node encodes n terms separating n+1 subtrees.  The
** subtree blocks are contiguous, so only the first subtree's blockid
** is encoded.  The subtree at iBlockid will contain all terms less
** than the first term encoded (or all terms if no term is encoded).
** Otherwise, for terms greater than or equal to pTerm[i] but less
** than pTerm[i+1], the subtree for that term will be rooted at
................................................................................
  n = getVarint(pData, &iBlockid);
  assert( n>0 );
  assert( n<=nData );
  pData += n;
  nData -= n;

  /* Zero or more terms of positive length */
  while( nData!=0 ){

    n = getVarint32(pData, &iDummy);
    assert( n>0 );
    assert( iDummy>0 );
    assert( n+iDummy>0);
    assert( n+iDummy<=nData );
    pData += n+iDummy;
    nData -= n+iDummy;




















  }
}
#define ASSERT_VALID_INTERIOR_BLOCK(x) interiorBlockValidate(x)
#else
#define ASSERT_VALID_INTERIOR_BLOCK(x) assert( 1 )
#endif

typedef struct InteriorWriter {
  int iHeight;                   /* from 0 at leaves. */
  InteriorBlock *first, *last;
  struct InteriorWriter *parentWriter;


  sqlite_int64 iOpeningChildBlock; /* First child block in block "last". */
#ifndef NDEBUG
  sqlite_int64 iLastChildBlock;  /* for consistency checks. */
#endif
} InteriorWriter;

/* Initialize an interior node where pTerm[nTerm] marks the leftmost
................................................................................
  pWriter->iOpeningChildBlock = iChildBlock;
#ifndef NDEBUG
  pWriter->iLastChildBlock = iChildBlock;
#endif
  block = interiorBlockNew(iHeight, iChildBlock, pTerm, nTerm);
  pWriter->last = pWriter->first = block;
  ASSERT_VALID_INTERIOR_BLOCK(pWriter->last);

}

/* Append the child node rooted at iChildBlock to the interior node,
** with pTerm[nTerm] as the leftmost term in iChildBlock's subtree.
*/
static void interiorWriterAppend(InteriorWriter *pWriter,
                                 const char *pTerm, int nTerm,
                                 sqlite_int64 iChildBlock){
  char c[VARINT_MAX+VARINT_MAX];
  int n = putVarint(c, nTerm);

  ASSERT_VALID_INTERIOR_BLOCK(pWriter->last);



















#ifndef NDEBUG
  pWriter->iLastChildBlock++;
#endif
  assert( pWriter->iLastChildBlock==iChildBlock );

  /* Overflow to a new block if the new term makes the current block
  ** too big, and the current block already has enough terms.
  */
  if( pWriter->last->data.nData+n+nTerm>INTERIOR_MAX &&
      iChildBlock-pWriter->iOpeningChildBlock>INTERIOR_MIN_TERMS ){
    pWriter->last->next = interiorBlockNew(pWriter->iHeight, iChildBlock,
                                           pTerm, nTerm);
    pWriter->last = pWriter->last->next;
    pWriter->iOpeningChildBlock = iChildBlock;

  }else{
    dataBufferAppend2(&pWriter->last->data, c, n, pTerm, nTerm);


  }
  ASSERT_VALID_INTERIOR_BLOCK(pWriter->last);
}

/* Free the space used by pWriter, including the linked-list of
** InteriorBlocks, and parentWriter, if present.
*/
................................................................................
    dataBufferDestroy(&b->data);
    free(b);
  }
  if( pWriter->parentWriter!=NULL ){
    interiorWriterDestroy(pWriter->parentWriter);
    free(pWriter->parentWriter);
  }

  SCRAMBLE(pWriter);
  return SQLITE_OK;
}

/* If pWriter can fit entirely in ROOT_MAX, return it as the root info
** directly, leaving *piEndBlockid unchanged.  Otherwise, flush
** pWriter to %_segments, building a new layer of interior nodes, and
................................................................................
  /* Parent node gets the chance to be the root. */
  return interiorWriterRootInfo(v, pWriter->parentWriter,
                                ppRootInfo, pnRootInfo, piEndBlockid);
}

/****************************************************************/
/* InteriorReader is used to read off the data from an interior node
** (see comment at top of file for the format).  InteriorReader does
** not own its data, so interiorReaderDestroy() is a formality.
*/
typedef struct InteriorReader {
  const char *pData;
  int nData;



  sqlite_int64 iBlockid;
} InteriorReader;

static void interiorReaderDestroy(InteriorReader *pReader){
  SCRAMBLE(pReader);
}

static void interiorReaderInit(const char *pData, int nData,
                               InteriorReader *pReader){
  int n;

  /* Require at least the leading flag byte */
  assert( nData>0 );
  assert( pData[0]!='\0' );

  CLEAR(pReader);

  /* Decode the base blockid, and set the cursor to the first term. */
  n = getVarint(pData+1, &pReader->iBlockid);
  assert( 1+n<=nData );
  pReader->pData = pData+1+n;
  pReader->nData = nData-(1+n);















}

static int interiorReaderAtEnd(InteriorReader *pReader){
  return pReader->nData<=0;
}

static sqlite_int64 interiorReaderCurrentBlockid(InteriorReader *pReader){
  return pReader->iBlockid;
}

static int interiorReaderTermBytes(InteriorReader *pReader){
  int nTerm;
  assert( !interiorReaderAtEnd(pReader) );
  getVarint32(pReader->pData, &nTerm);
  return nTerm;

}
static const char *interiorReaderTerm(InteriorReader *pReader){
  int n, nTerm;
  assert( !interiorReaderAtEnd(pReader) );
  n = getVarint32(pReader->pData, &nTerm);
  return pReader->pData+n;
}

/* Step forward to the next term in the node. */
static void interiorReaderStep(InteriorReader *pReader){
  int n, nTerm;
  assert( !interiorReaderAtEnd(pReader) );









  n = getVarint32(pReader->pData, &nTerm);






  assert( n+nTerm<=pReader->nData );
  pReader->pData += n+nTerm;
  pReader->nData -= n+nTerm;

  pReader->iBlockid++;
}

/* Compare the current term to pTerm[nTerm], returning strcmp-style
** results.
*/
static int interiorReaderTermCmp(InteriorReader *pReader,







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** InteriorReader.  InteriorWriters are created as needed when
** SegmentWriter creates new leaf nodes, or when an interior node
** itself grows too big and must be split.  The format of interior
** nodes:
**
** varint iHeight;           (height from leaf level, always >0)
** varint iBlockid;          (block id of node's leftmost subtree)
** optional {
**   varint nTerm;           (length of first term)
**   char pTerm[nTerm];      (content of first term)
**   array {
**                                (further terms are delta-encoded)
**     varint nPrefix;            (length of shared prefix with previous term)
**     varint nSuffix;            (length of unshared suffix)
**     char pTermSuffix[nSuffix]; (unshared suffix of next term)
**   }
** }
**
** Here, optional { X } means an optional element, while array { X }
** means zero or more occurrences of X, adjacent in memory.

**
** An interior node encodes n terms separating n+1 subtrees.  The
** subtree blocks are contiguous, so only the first subtree's blockid
** is encoded.  The subtree at iBlockid will contain all terms less
** than the first term encoded (or all terms if no term is encoded).
** Otherwise, for terms greater than or equal to pTerm[i] but less
** than pTerm[i+1], the subtree for that term will be rooted at
................................................................................
  n = getVarint(pData, &iBlockid);
  assert( n>0 );
  assert( n<=nData );
  pData += n;
  nData -= n;

  /* Zero or more terms of positive length */
  if( nData!=0 ){
    /* First term is not delta-encoded. */
    n = getVarint32(pData, &iDummy);
    assert( n>0 );
    assert( iDummy>0 );
    assert( n+iDummy>0);
    assert( n+iDummy<=nData );
    pData += n+iDummy;
    nData -= n+iDummy;

    /* Following terms delta-encoded. */
    while( nData!=0 ){
      /* Length of shared prefix. */
      n = getVarint32(pData, &iDummy);
      assert( n>0 );
      assert( iDummy>=0 );
      assert( n<nData );
      pData += n;
      nData -= n;

      /* Length and data of distinct suffix. */
      n = getVarint32(pData, &iDummy);
      assert( n>0 );
      assert( iDummy>0 );
      assert( n+iDummy>0);
      assert( n+iDummy<=nData );
      pData += n+iDummy;
      nData -= n+iDummy;
    }
  }
}
#define ASSERT_VALID_INTERIOR_BLOCK(x) interiorBlockValidate(x)
#else
#define ASSERT_VALID_INTERIOR_BLOCK(x) assert( 1 )
#endif

typedef struct InteriorWriter {
  int iHeight;                   /* from 0 at leaves. */
  InteriorBlock *first, *last;
  struct InteriorWriter *parentWriter;

  DataBuffer term;               /* Last term written to block "last". */
  sqlite_int64 iOpeningChildBlock; /* First child block in block "last". */
#ifndef NDEBUG
  sqlite_int64 iLastChildBlock;  /* for consistency checks. */
#endif
} InteriorWriter;

/* Initialize an interior node where pTerm[nTerm] marks the leftmost
................................................................................
  pWriter->iOpeningChildBlock = iChildBlock;
#ifndef NDEBUG
  pWriter->iLastChildBlock = iChildBlock;
#endif
  block = interiorBlockNew(iHeight, iChildBlock, pTerm, nTerm);
  pWriter->last = pWriter->first = block;
  ASSERT_VALID_INTERIOR_BLOCK(pWriter->last);
  dataBufferInit(&pWriter->term, 0);
}

/* Append the child node rooted at iChildBlock to the interior node,
** with pTerm[nTerm] as the leftmost term in iChildBlock's subtree.
*/
static void interiorWriterAppend(InteriorWriter *pWriter,
                                 const char *pTerm, int nTerm,
                                 sqlite_int64 iChildBlock){
  char c[VARINT_MAX+VARINT_MAX];
  int n, nPrefix = 0;

  ASSERT_VALID_INTERIOR_BLOCK(pWriter->last);

  /* The first term written into an interior node is actually
  ** associated with the second child added (the first child was added
  ** in interiorWriterInit, or in the if clause at the bottom of this
  ** function).  That term gets encoded straight up, with nPrefix left
  ** at 0.
  */
  if( pWriter->term.nData==0 ){
    n = putVarint(c, nTerm);
  }else{
    while( nPrefix<pWriter->term.nData &&
           pTerm[nPrefix]==pWriter->term.pData[nPrefix] ){
      nPrefix++;
    }

    n = putVarint(c, nPrefix);
    n += putVarint(c+n, nTerm-nPrefix);
  }

#ifndef NDEBUG
  pWriter->iLastChildBlock++;
#endif
  assert( pWriter->iLastChildBlock==iChildBlock );

  /* Overflow to a new block if the new term makes the current block
  ** too big, and the current block already has enough terms.
  */
  if( pWriter->last->data.nData+n+nTerm-nPrefix>INTERIOR_MAX &&
      iChildBlock-pWriter->iOpeningChildBlock>INTERIOR_MIN_TERMS ){
    pWriter->last->next = interiorBlockNew(pWriter->iHeight, iChildBlock,
                                           pTerm, nTerm);
    pWriter->last = pWriter->last->next;
    pWriter->iOpeningChildBlock = iChildBlock;
    dataBufferReset(&pWriter->term);
  }else{
    dataBufferAppend2(&pWriter->last->data, c, n,
                      pTerm+nPrefix, nTerm-nPrefix);
    dataBufferReplace(&pWriter->term, pTerm, nTerm);
  }
  ASSERT_VALID_INTERIOR_BLOCK(pWriter->last);
}

/* Free the space used by pWriter, including the linked-list of
** InteriorBlocks, and parentWriter, if present.
*/
................................................................................
    dataBufferDestroy(&b->data);
    free(b);
  }
  if( pWriter->parentWriter!=NULL ){
    interiorWriterDestroy(pWriter->parentWriter);
    free(pWriter->parentWriter);
  }
  dataBufferDestroy(&pWriter->term);
  SCRAMBLE(pWriter);
  return SQLITE_OK;
}

/* If pWriter can fit entirely in ROOT_MAX, return it as the root info
** directly, leaving *piEndBlockid unchanged.  Otherwise, flush
** pWriter to %_segments, building a new layer of interior nodes, and
................................................................................
  /* Parent node gets the chance to be the root. */
  return interiorWriterRootInfo(v, pWriter->parentWriter,
                                ppRootInfo, pnRootInfo, piEndBlockid);
}

/****************************************************************/
/* InteriorReader is used to read off the data from an interior node
** (see comment at top of file for the format).

*/
typedef struct InteriorReader {
  const char *pData;
  int nData;

  DataBuffer term;          /* previous term, for decoding term delta. */

  sqlite_int64 iBlockid;
} InteriorReader;

static void interiorReaderDestroy(InteriorReader *pReader){
  SCRAMBLE(pReader);
}

static void interiorReaderInit(const char *pData, int nData,
                               InteriorReader *pReader){
  int n, nTerm;

  /* Require at least the leading flag byte */
  assert( nData>0 );
  assert( pData[0]!='\0' );

  CLEAR(pReader);

  /* Decode the base blockid, and set the cursor to the first term. */
  n = getVarint(pData+1, &pReader->iBlockid);
  assert( 1+n<=nData );
  pReader->pData = pData+1+n;
  pReader->nData = nData-(1+n);

  /* A single-child interior node (such as when a leaf node was too
  ** large for the segment directory) won't have any terms.
  ** Otherwise, decode the first term.
  */
  if( pReader->nData==0 ){
    dataBufferInit(&pReader->term, 0);
  }else{
    n = getVarint32(pReader->pData, &nTerm);
    dataBufferInit(&pReader->term, nTerm);
    dataBufferReplace(&pReader->term, pReader->pData+n, nTerm);
    assert( n+nTerm<=pReader->nData );
    pReader->pData += n+nTerm;
    pReader->nData -= n+nTerm;
  }
}

static int interiorReaderAtEnd(InteriorReader *pReader){
  return pReader->term.nData==0;
}

static sqlite_int64 interiorReaderCurrentBlockid(InteriorReader *pReader){
  return pReader->iBlockid;
}

static int interiorReaderTermBytes(InteriorReader *pReader){

  assert( !interiorReaderAtEnd(pReader) );


  return pReader->term.nData;
}
static const char *interiorReaderTerm(InteriorReader *pReader){

  assert( !interiorReaderAtEnd(pReader) );

  return pReader->term.pData;
}

/* Step forward to the next term in the node. */
static void interiorReaderStep(InteriorReader *pReader){

  assert( !interiorReaderAtEnd(pReader) );

  /* If the last term has been read, signal eof, else construct the
  ** next term.
  */
  if( pReader->nData==0 ){
    dataBufferReset(&pReader->term);
  }else{
    int n, nPrefix, nSuffix;

    n = getVarint32(pReader->pData, &nPrefix);
    n += getVarint32(pReader->pData+n, &nSuffix);

    /* Truncate the current term and append suffix data. */
    pReader->term.nData = nPrefix;
    dataBufferAppend(&pReader->term, pReader->pData+n, nSuffix);

    assert( n+nSuffix<=pReader->nData );
    pReader->pData += n+nSuffix;
    pReader->nData -= n+nSuffix;
  }
  pReader->iBlockid++;
}

/* Compare the current term to pTerm[nTerm], returning strcmp-style
** results.
*/
static int interiorReaderTermCmp(InteriorReader *pReader,