SQLite

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.262 2007/11/05 05:12:53 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

    WHERETRACE(("Recomputing index info for %s...\n", pTab->zName));

    /* Count the number of possible WHERE clause constraints referring
    ** to this virtual table */
    for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
      if( pTerm->leftCursor != pSrc->iCursor ) continue;
      if( pTerm->eOperator==WO_IN ) continue;
      if( pTerm->eOperator==WO_ISNULL ) continue;
      nTerm++;
    }

    /* If the ORDER BY clause contains only columns in the current 
    ** virtual table then allocate space for the aOrderBy part of
    ** the sqlite3_index_info structure.
    */

    *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
    *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
                                                                     pUsage;

    for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
      if( pTerm->leftCursor != pSrc->iCursor ) continue;
      if( pTerm->eOperator==WO_IN ) continue;
      if( pTerm->eOperator==WO_ISNULL ) continue;
      pIdxCons[j].iColumn = pTerm->leftColumn;
      pIdxCons[j].iTermOffset = i;
      pIdxCons[j].op = pTerm->eOperator;
      /* The direct assignment in the previous line is possible only because
      ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical.  The
      ** following asserts verify this fact. */
      assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );

# 2006 June 10
#
# 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.
#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is creating and dropping virtual tables.
#
# $Id: vtab1.test,v 1.48 2007/11/05 05:12:53 danielk1977 Exp $

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

ifcapable !vtab||!schema_pragmas {
  finish_test
  return

do_test vtab1.12-5 {
  execsql { SELECT * FROM c }
} {3 G H}
do_test vtab1.12-6 {
  execsql { COMMIT }
  execsql { SELECT * FROM c }
} {3 G H}

# At one point (ticket #2759), a WHERE clause of the form "<column> IS NULL"
# on a virtual table was causing an assert() to fail in the compiler.
#
# "IS NULL" clauses should not be passed through to the virtual table
# implementation. They are handled by SQLite after the vtab returns it's
# data.
#
do_test vtab1.13-1 {
  execsql { 
    SELECT * FROM echo_c WHERE a IS NULL 
  }
} {}
do_test vtab1.13-2 {
  execsql { 
    INSERT INTO c VALUES(NULL, 15, 16);
    SELECT * FROM echo_c WHERE a IS NULL 
  }
} {{} 15 16}
do_test vtab1.13-3 {
  execsql { 
    INSERT INTO c VALUES(15, NULL, 16);
    SELECT * FROM echo_c WHERE b IS NULL 
  }
} {15 {} 16}
do_test vtab1.13-3 {
  execsql { 
    SELECT * FROM echo_c WHERE b IS NULL AND a = 15;
  }
} {15 {} 16}

unset -nocomplain echo_module_begin_fail
finish_test