SQLite

** Return true if pTerm is a virtual table LIMIT or OFFSET term.
*/
static int isLimitTerm(WhereTerm *pTerm){
  assert( pTerm->eOperator==WO_AUX || pTerm->eMatchOp==0 );
  return pTerm->eMatchOp>=SQLITE_INDEX_CONSTRAINT_LIMIT
      && pTerm->eMatchOp<=SQLITE_INDEX_CONSTRAINT_OFFSET;
}

/*
** Return true if the first nCons constraints in the pUsage array are
** marked as in-use (have argvIndex>0). False otherwise.
*/
static int allConstraintsUsed(
  struct sqlite3_index_constraint_usage *aUsage, 
  int nCons
){
  int ii;
  for(ii=0; ii<nCons; ii++){
    if( aUsage[ii].argvIndex<=0 ) return 0;
  }
  return 1;
}

/*
** Argument pIdxInfo is already populated with all constraints that may
** be used by the virtual table identified by pBuilder->pNew->iTab. This
** function marks a subset of those constraints usable, invokes the
** xBestIndex method and adds the returned plan to pBuilder.
**

        ** (2) Multiple outputs from a single IN value will not merge
        ** together.  */
        pIdxInfo->orderByConsumed = 0;
        pIdxInfo->idxFlags &= ~SQLITE_INDEX_SCAN_UNIQUE;
        *pbIn = 1; assert( (mExclude & WO_IN)==0 );
      }

      /* Unless pbRetryLimit is non-NULL, there should be no LIMIT/OFFSET
      ** terms. And if there are any, they should follow all other terms. */
      assert( pbRetryLimit || !isLimitTerm(pTerm) );
      assert( !isLimitTerm(pTerm) || i>=nConstraint-2 );
      assert( !isLimitTerm(pTerm) || i==nConstraint-1 || isLimitTerm(pTerm+1) );

      if( isLimitTerm(pTerm) && (*pbIn || !allConstraintsUsed(pUsage, i)) ){
        /* If there is an IN(...) term handled as an == (separate call to
        ** xFilter for each value on the RHS of the IN) and a LIMIT or
        ** OFFSET term handled as well, the plan is unusable. Similarly,
        ** if there is a LIMIT/OFFSET and there are other unused terms,
        ** the plan cannot be used. In these cases set variable *pbRetryLimit
        ** to true to tell the caller to retry with LIMIT and OFFSET 
        ** disabled. */
        if( pIdxInfo->needToFreeIdxStr ){
          sqlite3_free(pIdxInfo->idxStr);
          pIdxInfo->idxStr = 0;
          pIdxInfo->needToFreeIdxStr = 0;
        }
        *pbRetryLimit = 1;
        return SQLITE_OK;

# 2024-04-26
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# 
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix bestindexC

ifcapable !vtab {
  finish_test
  return
}

register_tcl_module db

  SELECT * FROM y1 WHERE a = '2' LIMIT 3
} {2}

load_static_extension db series
do_execsql_test 3.3 {
  SELECT * FROM generate_series(1, 5) WHERE value = (value & 14) LIMIT 3
} {2 4}

do_execsql_test 3.4 {
  SELECT value FROM generate_series(1,10) WHERE value>2 LIMIT 4 OFFSET 1;
} {4 5 6 7}

finish_test