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Overview
Comment:Minor optimization for fts5 API xInst().
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SHA1: efb7c9c5d0015c8c966f8d6742c05cda82fc146a
User & Date: dan 2015-08-12 15:36:58
Context
2015-08-13
11:46
Avoid invoking system call unlink() directly from RBU code. Use the xDelete method of the default VFS instead. check-in: ee966af8 user: dan tags: trunk
2015-08-12
19:42
Avoid reading frames that have already been checkpointed from the wal file. check-in: 5669ac4a user: dan tags: wal-read-change
15:36
Minor optimization for fts5 API xInst(). check-in: efb7c9c5 user: dan tags: trunk
12:11
Add the xPhraseFirst() and xPhraseNext() fts5 APIs, for faster iteration through a single phrases position list. Also optimize xInst() and xInstCount() a bit. check-in: f7682435 user: dan tags: trunk
Changes
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Changes to ext/fts5/fts5_main.c.

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/*
** Ensure that the Fts5Cursor.nInstCount and aInst[] variables are populated
** correctly for the current view. Return SQLITE_OK if successful, or an
** SQLite error code otherwise.
*/
static int fts5CacheInstArray(Fts5Cursor *pCsr){
  int rc = SQLITE_OK;
  if( CsrFlagTest(pCsr, FTS5CSR_REQUIRE_INST) ){
    Fts5PoslistReader *aIter;     /* One iterator for each phrase */
    int nIter;                    /* Number of iterators/phrases */
    
    nIter = sqlite3Fts5ExprPhraseCount(pCsr->pExpr);
    if( pCsr->aInstIter==0 ){
      int nByte = sizeof(Fts5PoslistReader) * nIter;
      pCsr->aInstIter = (Fts5PoslistReader*)sqlite3Fts5MallocZero(&rc, nByte);
    }
    aIter = pCsr->aInstIter;

    if( aIter ){
      int nInst = 0;              /* Number instances seen so far */
      int i;

      /* Initialize all iterators */
      for(i=0; i<nIter; i++){
        const u8 *a;
        int n = fts5CsrPoslist(pCsr, i, &a);
        sqlite3Fts5PoslistReaderInit(-1, a, n, &aIter[i]);
      }

      while( 1 ){
        int *aInst;
        int iBest = -1;
        for(i=0; i<nIter; i++){
          if( (aIter[i].bEof==0) 
           && (iBest<0 || aIter[i].iPos<aIter[iBest].iPos) 
          ){
            iBest = i;
          }
        }
        if( iBest<0 ) break;

        nInst++;
        if( nInst>=pCsr->nInstAlloc ){
          pCsr->nInstAlloc = pCsr->nInstAlloc ? pCsr->nInstAlloc*2 : 32;
          aInst = (int*)sqlite3_realloc(
              pCsr->aInst, pCsr->nInstAlloc*sizeof(int)*3
          );
          if( aInst ){
            pCsr->aInst = aInst;
          }else{
            rc = SQLITE_NOMEM;
            break;
          }
        }

        aInst = &pCsr->aInst[3 * (nInst-1)];
        aInst[0] = iBest;
        aInst[1] = FTS5_POS2COLUMN(aIter[iBest].iPos);
        aInst[2] = FTS5_POS2OFFSET(aIter[iBest].iPos);
        sqlite3Fts5PoslistReaderNext(&aIter[iBest]);
      }

      pCsr->nInstCount = nInst;
      CsrFlagClear(pCsr, FTS5CSR_REQUIRE_INST);
    }
  }
  return rc;
}

static int fts5ApiInstCount(Fts5Context *pCtx, int *pnInst){
  Fts5Cursor *pCsr = (Fts5Cursor*)pCtx;
  int rc;

  if( SQLITE_OK==(rc = fts5CacheInstArray(pCsr)) ){
    *pnInst = pCsr->nInstCount;
  }
  return rc;
}

static int fts5ApiInst(
  Fts5Context *pCtx, 
  int iIdx, 
  int *piPhrase, 
  int *piCol, 
  int *piOff
){
  Fts5Cursor *pCsr = (Fts5Cursor*)pCtx;
  int rc;

  if( SQLITE_OK==(rc = fts5CacheInstArray(pCsr)) ){

    if( iIdx<0 || iIdx>=pCsr->nInstCount ){
      rc = SQLITE_RANGE;
    }else{
      *piPhrase = pCsr->aInst[iIdx*3];
      *piCol = pCsr->aInst[iIdx*3 + 1];
      *piOff = pCsr->aInst[iIdx*3 + 2];
    }







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/*
** Ensure that the Fts5Cursor.nInstCount and aInst[] variables are populated
** correctly for the current view. Return SQLITE_OK if successful, or an
** SQLite error code otherwise.
*/
static int fts5CacheInstArray(Fts5Cursor *pCsr){
  int rc = SQLITE_OK;

  Fts5PoslistReader *aIter;       /* One iterator for each phrase */
  int nIter;                      /* Number of iterators/phrases */
  
  nIter = sqlite3Fts5ExprPhraseCount(pCsr->pExpr);
  if( pCsr->aInstIter==0 ){
    int nByte = sizeof(Fts5PoslistReader) * nIter;
    pCsr->aInstIter = (Fts5PoslistReader*)sqlite3Fts5MallocZero(&rc, nByte);
  }
  aIter = pCsr->aInstIter;

  if( aIter ){
    int nInst = 0;                /* Number instances seen so far */
    int i;

    /* Initialize all iterators */
    for(i=0; i<nIter; i++){
      const u8 *a;
      int n = fts5CsrPoslist(pCsr, i, &a);
      sqlite3Fts5PoslistReaderInit(-1, a, n, &aIter[i]);
    }

    while( 1 ){
      int *aInst;
      int iBest = -1;
      for(i=0; i<nIter; i++){
        if( (aIter[i].bEof==0) 
         && (iBest<0 || aIter[i].iPos<aIter[iBest].iPos) 
        ){
          iBest = i;
        }
      }
      if( iBest<0 ) break;

      nInst++;
      if( nInst>=pCsr->nInstAlloc ){
        pCsr->nInstAlloc = pCsr->nInstAlloc ? pCsr->nInstAlloc*2 : 32;
        aInst = (int*)sqlite3_realloc(
            pCsr->aInst, pCsr->nInstAlloc*sizeof(int)*3
        );
        if( aInst ){
          pCsr->aInst = aInst;
        }else{
          rc = SQLITE_NOMEM;
          break;
        }
      }

      aInst = &pCsr->aInst[3 * (nInst-1)];
      aInst[0] = iBest;
      aInst[1] = FTS5_POS2COLUMN(aIter[iBest].iPos);
      aInst[2] = FTS5_POS2OFFSET(aIter[iBest].iPos);
      sqlite3Fts5PoslistReaderNext(&aIter[iBest]);
    }

    pCsr->nInstCount = nInst;
    CsrFlagClear(pCsr, FTS5CSR_REQUIRE_INST);

  }
  return rc;
}

static int fts5ApiInstCount(Fts5Context *pCtx, int *pnInst){
  Fts5Cursor *pCsr = (Fts5Cursor*)pCtx;
  int rc = SQLITE_OK;
  if( CsrFlagTest(pCsr, FTS5CSR_REQUIRE_INST)==0 
   || SQLITE_OK==(rc = fts5CacheInstArray(pCsr)) ){
    *pnInst = pCsr->nInstCount;
  }
  return rc;
}

static int fts5ApiInst(
  Fts5Context *pCtx, 
  int iIdx, 
  int *piPhrase, 
  int *piCol, 
  int *piOff
){
  Fts5Cursor *pCsr = (Fts5Cursor*)pCtx;
  int rc = SQLITE_OK;
  if( CsrFlagTest(pCsr, FTS5CSR_REQUIRE_INST)==0 
   || SQLITE_OK==(rc = fts5CacheInstArray(pCsr)) 
  ){
    if( iIdx<0 || iIdx>=pCsr->nInstCount ){
      rc = SQLITE_RANGE;
    }else{
      *piPhrase = pCsr->aInst[iIdx*3];
      *piCol = pCsr->aInst[iIdx*3 + 1];
      *piOff = pCsr->aInst[iIdx*3 + 2];
    }