SQLite

      rc = fts3TruncateSegment(p, iAbsLevel, pSeg->iIdx, zTerm, nTerm);
    }
  }

  return rc;
}

/*
** Attempt an incremental merge that writes nMerge leaf pages.
**
** Incremental merges happen two segments at a time.  The two
** segments to be merged are the two oldest segments (the ones with
** the smallest index) in the highest level that has at least
** nMin segments.  Multiple segment pair merges might occur in
** an attempt to write the quota of nMerge leaf pages.
*/
static int fts3Incrmerge(Fts3Table *p, int nMerge, int nMin){
  int rc = SQLITE_OK;             /* Return code */
  int nRem = nMerge;              /* Number of leaf pages yet to  be written */

  assert( nMin>=2 );

  while( rc==SQLITE_OK && nRem>0 ){
    sqlite3_int64 iAbsLevel;        /* Absolute level number to work on */
    sqlite3_stmt *pFindLevel = 0;   /* SQL used to determine iAbsLevel */
    Fts3MultiSegReader csr;         /* Cursor used to read input data */

      return sqlite3_reset(pFindLevel);
    }
    iAbsLevel = sqlite3_column_int64(pFindLevel, 0);
    rc = sqlite3_reset(pFindLevel);
    if( rc!=SQLITE_OK ) return rc;

    /* Open a cursor to iterate through the contents of indexes 0 and 1 of
    ** the selected absolute level. */
    rc = fts3IncrmergeCsr(p, iAbsLevel, &csr);
    if( rc!=SQLITE_OK ) return rc;
    memset(&filter, 0, sizeof(Fts3SegFilter));
    filter.flags = FTS3_SEGMENT_REQUIRE_POS;

    rc = sqlite3Fts3SegReaderStart(p, &csr, &filter);
    assert( rc!=SQLITE_ABORT );
    if( SQLITE_ROW==(rc = sqlite3Fts3SegReaderStep(p, &csr)) ){
      rc = fts3IncrmergeWriter(p, iAbsLevel, csr.zTerm, csr.nTerm, &writer);
      assert( rc!=SQLITE_ABORT );
      if( rc==SQLITE_OK ){
        do {
          rc = fts3IncrmergeAppend(p, &writer, &csr);
          assert( rc!=SQLITE_ABORT );
          if( rc==SQLITE_OK ) rc = sqlite3Fts3SegReaderStep(p, &csr);
          assert( rc!=SQLITE_ABORT );
          if( writer.nWork>=nRem && rc==SQLITE_ROW ) rc = SQLITE_OK;
        }while( rc==SQLITE_ROW );
      }
    }
    assert( rc!=SQLITE_ABORT );
    fts3IncrmergeRelease(p, &writer, &rc);
    nRem -= (1 + writer.nWork);

    /* Update or delete the input segments */
    if( rc==SQLITE_OK ){
      rc = fts3IncrmergeChomp(p, iAbsLevel, &csr);
    }

    sqlite3Fts3SegReaderFinish(&csr);
  }

  return rc;
}

/*
** Process statements of the form:


**
**    INSERT INTO table(table) VALUES('merge=A,B');
**
** A and B are integers that decode to be the number of leaf pages
** written for the merge, and the minimum number of segments on a level
** before it will be selected for a merge, respectively.
*/
static int fts3DoIncrmerge(Fts3Table *p, const char *zParam){
  int rc;
  int nMin = (FTS3_MERGE_COUNT / 2);
  int nMerge = 0;
  const char *z = zParam;

  /* Read the first integer value */
  for(z=zParam; z[0]>='0' && z[0]<='9'; z++){
    nMerge = nMerge * 10 + (z[0] - '0');
  }

  /* If the first integer value is followed by a ',',  read the second
  ** integer value. */
  if( z[0]==',' && z[1]!='\0' ){
    z++;
    nMin = 0;
    while( z[0]>='0' && z[0]<='9' ){
      nMin = nMin * 10 + (z[0] - '0');
      z++;
    }
  }

  if( z[0]!='\0' ) return SQLITE_ERROR;
  if( nMin<2 ) nMin = 2;