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 1.168 2005/09/01 17:47:51 drh Exp $
*/
#include "sqliteInt.h"

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

  int *pbRev              /* Set to 1 if ORDER BY is DESC */
){
  Expr *p;

  assert( pOrderBy!=0 );
  assert( pOrderBy->nExpr>0 );
  p = pOrderBy->a[0].pExpr;
  if( pOrderBy->nExpr==1 && p->op==TK_COLUMN && p->iTable==base
          && p->iColumn==-1 ){
    *pbRev = pOrderBy->a[0].sortOrder;
    return 1;
  }
  return 0;
}

/*

# 2001 September 15.
#
# 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 testing the CREATE TABLE statement.
#
# $Id: sort.test,v 1.23 2005/09/01 17:47:52 drh Exp $

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

# Create a bunch of data to sort against
#
do_test sort-1.0 {

    insert into t8 values(2,3,4);
    create table t9(x,y);
    insert into t9 values(2,4);
    insert into t9 values(2,3);
    select y from t8, t9 where a=1 order by a, y;
  }
} {3 4}

# Trouble reported on the mailing list.  Check for overly aggressive
# (which is to say, incorrect) optimization of order-by with a rowid
# in a join.
#
do_test sort-12.1 {
  execsql {
    create table a (id integer primary key);
    create table b (id integer primary key, aId integer, text);
    insert into a values (1);
    insert into b values (2, 1, 'xxx');
    insert into b values (1, 1, 'zzz');
    insert into b values (3, 1, 'yyy');
    select a.id, b.id, b.text from a join b on (a.id = b.aId)
      order by a.id, b.text;
  }
} {1 2 xxx 1 3 yyy 1 1 zzz}

finish_test

# 2001 September 15
#
# 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 testing the use of indices in WHERE clases.
#
# $Id: where.test,v 1.35 2005/09/01 17:47:52 drh Exp $

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

# Build some test data
#
do_test where-1.0 {

    SELECT y FROM t1 ORDER BY rowid LIMIT 3;
  }
} {4 9 16 nosort}
do_test where-6.21 {
  cksort {
    SELECT y FROM t1 ORDER BY rowid, y LIMIT 3;
  }
} {4 9 16 sort}
do_test where-6.22 {
  cksort {
    SELECT y FROM t1 ORDER BY rowid, y DESC LIMIT 3;
  }
} {4 9 16 sort}
do_test where-6.23 {
  cksort {
    SELECT y FROM t1 WHERE y>4 ORDER BY rowid, w, x LIMIT 3;
  }
} {9 16 25 sort}
do_test where-6.24 {
  cksort {
    SELECT y FROM t1 WHERE y>=9 ORDER BY rowid, x DESC, w LIMIT 3;
  }
} {9 16 25 sort}
do_test where-6.25 {
  cksort {
    SELECT y FROM t1 WHERE y>4 AND y<25 ORDER BY rowid;
  }
} {9 16 nosort}
do_test where-6.26 {
  cksort {
    SELECT y FROM t1 WHERE y>=4 AND y<=25 ORDER BY oid;
  }
} {4 9 16 25 nosort}
do_test where-6.27 {
  cksort {
    SELECT y FROM t1 WHERE y<=25 ORDER BY _rowid_, w+y;
  }
} {4 9 16 25 sort}


# Tests for reverse-order sorting.
#
do_test where-7.1 {
  cksort {
    SELECT w FROM t1 WHERE x=3 ORDER BY y;

do_test where-7.31 {
  cksort {
    SELECT y FROM t1 ORDER BY rowid DESC LIMIT 3
  }
} {10201 10000 9801 nosort}
do_test where-7.32 {
  cksort {
    SELECT y FROM t1 WHERE y<25 ORDER BY rowid DESC
  }
} {16 9 4 nosort}
do_test where-7.33 {
  cksort {
    SELECT y FROM t1 WHERE y<=25 ORDER BY rowid DESC
  }
} {25 16 9 4 nosort}
do_test where-7.34 {
  cksort {
    SELECT y FROM t1 WHERE y<25 AND y>4 ORDER BY rowid DESC, y DESC
  }
} {16 9 sort}
do_test where-7.35 {
  cksort {
    SELECT y FROM t1 WHERE y<25 AND y>=4 ORDER BY rowid DESC
  }
} {16 9 4 nosort}

do_test where-8.1 {