SQLite

** once prior to any call to seriesColumn() or seriesRowid() or
** seriesEof().
**
** The query plan selected by seriesBestIndex is passed in the idxNum
** parameter.  (idxStr is not used in this implementation.)  idxNum
** is a bitmask showing which constraints are available:
**
**   0x01:    start=VALUE
**   0x02:    stop=VALUE
**   0x04:    step=VALUE


**   0x08:    descending order
**   0x10:    ascending order
**   0x20:    LIMIT  VALUE
**   0x40:    OFFSET  VALUE
**
** This routine should initialize the cursor and position it so that it
** is pointing at the first row, or pointing off the end of the table
** (so that seriesEof() will return true) if the table is empty.
*/
static int seriesFilter(
  sqlite3_vtab_cursor *pVtabCursor,
  int idxNum, const char *idxStrUnused,
  int argc, sqlite3_value **argv
){
  series_cursor *pCur = (series_cursor *)pVtabCursor;
  int i = 0;
  (void)idxStrUnused;
  if( idxNum & 0x01 ){
    pCur->ss.iBase = sqlite3_value_int64(argv[i++]);
  }else{
    pCur->ss.iBase = 0;
  }
  if( idxNum & 0x02 ){
    pCur->ss.iTerm = sqlite3_value_int64(argv[i++]);
  }else{
    pCur->ss.iTerm = 0xffffffff;
  }
  if( idxNum & 0x04 ){
    pCur->ss.iStep = sqlite3_value_int64(argv[i++]);
    if( pCur->ss.iStep==0 ){
      pCur->ss.iStep = 1;
    }else if( pCur->ss.iStep<0 ){
      if( (idxNum & 16)==0 ) idxNum |= 8;
    }
  }else{
    pCur->ss.iStep = 1;
  }
  if( idxNum & 0x20 ){
    sqlite3_int64 iLimit = sqlite3_value_int64(argv[i++]);
    sqlite3_int64 iTerm;
    if( idxNum & 0x40 ){
      sqlite3_int64 iOffset = sqlite3_value_int64(argv[i++]);
      if( iOffset>0 ){
        pCur->ss.iBase += pCur->ss.iStep*iOffset;
      }
    }
    if( iLimit>=0 ){
      iTerm = pCur->ss.iBase + (iLimit - 1)*pCur->ss.iStep;
      if( pCur->ss.iStep<0 ){
        if( iTerm>pCur->ss.iTerm ) pCur->ss.iTerm = iTerm;
      }else{
        if( iTerm<pCur->ss.iTerm ) pCur->ss.iTerm = iTerm;
      }
    }
  }
  for(i=0; i<argc; i++){
    if( sqlite3_value_type(argv[i])==SQLITE_NULL ){
      /* If any of the constraints have a NULL value, then return no rows.
      ** See ticket https://www.sqlite.org/src/info/fac496b61722daf2 */
      pCur->ss.iBase = 1;
      pCur->ss.iTerm = 0;
      pCur->ss.iStep = 1;
      break;
    }
  }
  if( idxNum & 0x08 ){
    pCur->ss.isReversing = pCur->ss.iStep > 0;
  }else{
    pCur->ss.isReversing = pCur->ss.iStep < 0;
  }
  setupSequence( &pCur->ss );
  return SQLITE_OK;
}

/*
** SQLite will invoke this method one or more times while planning a query
** that uses the generate_series virtual table.  This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
**
** In this implementation idxNum is used to represent the
** query plan.  idxStr is unused.
**
** The query plan is represented by bits in idxNum:
**
**   0x01  start = $value  -- constraint exists
**   0x02  stop = $value   -- constraint exists
**   0x04  step = $value   -- constraint exists
**   0x08  output is in descending order
**   0x10  output is in ascending order
**   0x20  LIMIT $value    -- constraint exists
**   0x40  OFFSET $value   -- constraint exists
*/
static int seriesBestIndex(
  sqlite3_vtab *pVTab,
  sqlite3_index_info *pIdxInfo
){
  int i, j;              /* Loop over constraints */
  int idxNum = 0;        /* The query plan bitmask */
  int bStartSeen = 0;    /* EQ constraint seen on the START column */
  int unusableMask = 0;  /* Mask of unusable constraints */
  int nArg = 0;          /* Number of arguments that seriesFilter() expects */
  int aIdx[5];           /* Constraints on start, stop, step, LIMIT, OFFSET */
  const struct sqlite3_index_constraint *pConstraint;

  /* This implementation assumes that the start, stop, and step columns
  ** are the last three columns in the virtual table. */
  assert( SERIES_COLUMN_STOP == SERIES_COLUMN_START+1 );
  assert( SERIES_COLUMN_STEP == SERIES_COLUMN_START+2 );

  aIdx[0] = aIdx[1] = aIdx[2] = aIdx[3] = aIdx[4] = -1;
  pConstraint = pIdxInfo->aConstraint;
  for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
    int iCol;    /* 0 for start, 1 for stop, 2 for step */
    int iMask;   /* bitmask for those column */
    int op = pConstraint->op;
    if( op!=SQLITE_INDEX_CONSTRAINT_EQ ){
      if( op==SQLITE_INDEX_CONSTRAINT_LIMIT ){
        aIdx[3] = i;
        idxNum |= 0x20;
      }else if( op==SQLITE_INDEX_CONSTRAINT_OFFSET ){
        aIdx[4] = i;
        idxNum |= 0x40;
      }
      continue;
    }
    if( pConstraint->iColumn<SERIES_COLUMN_START ) continue;
    iCol = pConstraint->iColumn - SERIES_COLUMN_START;
    assert( iCol>=0 && iCol<=2 );
    iMask = 1 << iCol;
    if( iCol==0 ) bStartSeen = 1;
    if( pConstraint->usable==0 ){
      unusableMask |=  iMask;
      continue;
    }else if( pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ ){
      idxNum |= iMask;
      aIdx[iCol] = i;
    }
  }
  if( aIdx[3]==0 ){
    /* Ignore OFFSET if LIMIT is omitted */
    idxNum &= ~0x60;
    aIdx[4] = 0;
  }
  for(i=0; i<5; i++){
    if( (j = aIdx[i])>=0 ){
      pIdxInfo->aConstraintUsage[j].argvIndex = ++nArg;
      pIdxInfo->aConstraintUsage[j].omit =
         !SQLITE_SERIES_CONSTRAINT_VERIFY || i>=3;
    }
  }
  /* The current generate_column() implementation requires at least one
  ** argument (the START value).  Legacy versions assumed START=0 if the
  ** first argument was omitted.  Compile with -DZERO_ARGUMENT_GENERATE_SERIES
  ** to obtain the legacy behavior */
#ifndef ZERO_ARGUMENT_GENERATE_SERIES

  if( (idxNum & 3)==3 ){
    /* Both start= and stop= boundaries are available.  This is the 
    ** the preferred case */
    pIdxInfo->estimatedCost = (double)(2 - ((idxNum&4)!=0));
    pIdxInfo->estimatedRows = 1000;
    if( pIdxInfo->nOrderBy>=1 && pIdxInfo->aOrderBy[0].iColumn==0 ){
      if( pIdxInfo->aOrderBy[0].desc ){
        idxNum |= 0x08;
      }else{
        idxNum |= 0x10;
      }
      pIdxInfo->orderByConsumed = 1;
    }
  }else{
    /* If either boundary is missing, we have to generate a huge span
    ** of numbers.  Make this case very expensive so that the query
    ** planner will work hard to avoid it. */

  } {1 {table pragma_compile_options may not be altered}}
  do_test tabfunc01-930 {
    catchsql {
      ALTER TABLE pragma_compile_options DROP COLUMN start;
    }
  } {1 {table pragma_compile_options may not be altered}}
}

#-----------------------------------------------------------------------------
# 2024-04-26  LIMIT and OFFSET passed into virtual tables
# https://sqlite.org/forum/forumpost/c243b8f856
#
do_execsql_test tabfunc01-900 {
  SELECT * FROM (
    SELECT * FROM generate_series(1,10)
    UNION ALL
    SELECT * FROM generate_series(101,104)
  ) LIMIT 10 OFFSET 5;
} {6 7 8 9 10 101 102 103 104}
do_execsql_test tabfunc01-910 {
  SELECT * FROM (
    SELECT * FROM generate_series(1,10)
    UNION ALL
    SELECT * FROM generate_series(101,104)
  ) LIMIT -1 OFFSET 5;
} {6 7 8 9 10 101 102 103 104}
do_execsql_test tabfunc01-920 {
  SELECT * FROM (
    SELECT * FROM generate_series(1,10)
    UNION ALL
    SELECT * FROM generate_series(101,104)
  ) LIMIT -1 OFFSET 0;
} {1 2 3 4 5 6 7 8 9 10 101 102 103 104}


# Free up memory allocations
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