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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);
................................................................................
        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);
................................................................................
      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];
    }