/ Check-in [f9a7e179]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Do more aggressive optimization of the AND operator where one side or the other is always false.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: f9a7e179cbbeeab5e57bbf392bef89750215546b
User & Date: drh 2012-03-31 02:34:35
Context
2012-03-31
09:59
Fix a bug in the EXPLAIN code for listing trigger programs that was causing an out-of-bounds read. check-in: c9342ca5 user: dan tags: trunk
02:46
Merge all the latest trunk changes into the apple-osx branch. check-in: 18ec60ca user: drh tags: apple-osx
02:34
Do more aggressive optimization of the AND operator where one side or the other is always false. check-in: f9a7e179 user: drh tags: trunk
2012-03-30
16:44
Avoid using the OVERLAPPED struct on WinCE. check-in: 196ca3a8 user: mistachkin tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/expr.c.

480
481
482
483
484
485
486





487
488

489
490
491
492
493


















494
495
496
497




498
499
500
501
502
503




504
505
506
507
508
509
510
Expr *sqlite3PExpr(
  Parse *pParse,          /* Parsing context */
  int op,                 /* Expression opcode */
  Expr *pLeft,            /* Left operand */
  Expr *pRight,           /* Right operand */
  const Token *pToken     /* Argument token */
){





  Expr *p = sqlite3ExprAlloc(pParse->db, op, pToken, 1);
  sqlite3ExprAttachSubtrees(pParse->db, p, pLeft, pRight);

  if( p ) {
    sqlite3ExprCheckHeight(pParse, p->nHeight);
  }
  return p;
}



















/*
** Join two expressions using an AND operator.  If either expression is
** NULL, then just return the other expression.




*/
Expr *sqlite3ExprAnd(sqlite3 *db, Expr *pLeft, Expr *pRight){
  if( pLeft==0 ){
    return pRight;
  }else if( pRight==0 ){
    return pLeft;




  }else{
    Expr *pNew = sqlite3ExprAlloc(db, TK_AND, 0, 0);
    sqlite3ExprAttachSubtrees(db, pNew, pLeft, pRight);
    return pNew;
  }
}








>
>
>
>
>
|
|
>





>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>




>
>
>
>






>
>
>
>







480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
Expr *sqlite3PExpr(
  Parse *pParse,          /* Parsing context */
  int op,                 /* Expression opcode */
  Expr *pLeft,            /* Left operand */
  Expr *pRight,           /* Right operand */
  const Token *pToken     /* Argument token */
){
  Expr *p;
  if( op==TK_AND && pLeft && pRight ){
    /* Take advantage of short-circuit false optimization for AND */
    p = sqlite3ExprAnd(pParse->db, pLeft, pRight);
  }else{
    p = sqlite3ExprAlloc(pParse->db, op, pToken, 1);
    sqlite3ExprAttachSubtrees(pParse->db, p, pLeft, pRight);
  }
  if( p ) {
    sqlite3ExprCheckHeight(pParse, p->nHeight);
  }
  return p;
}

/*
** Return 1 if an expression must be FALSE in all cases and 0 if the
** expression might be true.  This is an optimization.  If is OK to
** return 0 here even if the expression really is always false (a 
** false negative).  But it is a bug to return 1 if the expression
** might be true in some rare circumstances (a false positive.)
**
** Note that if the expression is part of conditional for a
** LEFT JOIN, then we cannot determine at compile-time whether or not
** is it true or false, so always return 0.
*/
static int exprAlwaysFalse(Expr *p){
  int v = 0;
  if( ExprHasProperty(p, EP_FromJoin) ) return 0;
  if( !sqlite3ExprIsInteger(p, &v) ) return 0;
  return v==0;
}

/*
** Join two expressions using an AND operator.  If either expression is
** NULL, then just return the other expression.
**
** If one side or the other of the AND is known to be false, then instead
** of returning an AND expression, just return a constant expression with
** a value of false.
*/
Expr *sqlite3ExprAnd(sqlite3 *db, Expr *pLeft, Expr *pRight){
  if( pLeft==0 ){
    return pRight;
  }else if( pRight==0 ){
    return pLeft;
  }else if( exprAlwaysFalse(pLeft) || exprAlwaysFalse(pRight) ){
    sqlite3ExprDelete(db, pLeft);
    sqlite3ExprDelete(db, pRight);
    return sqlite3ExprAlloc(db, TK_INTEGER, &sqlite3IntTokens[0], 0);
  }else{
    Expr *pNew = sqlite3ExprAlloc(db, TK_AND, 0, 0);
    sqlite3ExprAttachSubtrees(db, pNew, pLeft, pRight);
    return pNew;
  }
}

Changes to test/in.test.

254
255
256
257
258
259
260
261
262
263
264
265



266
267
268
269
270









271
272
273
274
275
276
277
  }
} {}
do_test in-7.5 {
  execsql {
    SELECT a FROM t1 WHERE a IN (5) AND b NOT IN ();
  }
} {5}
do_test in-7.6 {
  execsql {
    SELECT a FROM ta WHERE a IN ();
  }
} {}



do_test in-7.7 {
  execsql {
    SELECT a FROM ta WHERE a NOT IN ();
  }
} {1 2 3 4 6 8 10}










do_test in-8.1 {
  execsql {
    SELECT b FROM t1 WHERE a IN ('hello','there')
  }
} {world}
do_test in-8.2 {







|




>
>
>





>
>
>
>
>
>
>
>
>







254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
  }
} {}
do_test in-7.5 {
  execsql {
    SELECT a FROM t1 WHERE a IN (5) AND b NOT IN ();
  }
} {5}
do_test in-7.6.1 {
  execsql {
    SELECT a FROM ta WHERE a IN ();
  }
} {}
do_test in-7.6.2 {
  db status step
} {0}
do_test in-7.7 {
  execsql {
    SELECT a FROM ta WHERE a NOT IN ();
  }
} {1 2 3 4 6 8 10}

do_test in-7.8.1 {
  execsql {
    SELECT * FROM ta LEFT JOIN tb ON (ta.b=tb.b) WHERE ta.a IN ();
  }
} {}
do_test in-7.8.2 {
  db status step
} {0}

do_test in-8.1 {
  execsql {
    SELECT b FROM t1 WHERE a IN ('hello','there')
  }
} {world}
do_test in-8.2 {