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Commit71f2993

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Fix transformExpr() to not scribble on its input datastructure while
transforming CASE expressions. This was definitely confusingFigureColname, and might lead to bad things elsewhere as well.
1 parent1c7bef3 commit71f2993

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1 file changed

+57
-49
lines changed

1 file changed

+57
-49
lines changed

‎src/backend/parser/parse_expr.c‎

Lines changed: 57 additions & 49 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.102 2001/09/28 08:09:09 thomas Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.103 2001/10/08 21:46:59 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -426,15 +426,23 @@ transformExpr(ParseState *pstate, Node *expr, int precedence)
426426
caseT_CaseExpr:
427427
{
428428
CaseExpr*c= (CaseExpr*)expr;
429-
CaseWhen*w;
429+
CaseExpr*newc=makeNode(CaseExpr);
430+
List*newargs=NIL;
430431
List*typeids=NIL;
431432
List*args;
433+
Node*defresult;
432434
Oidptype;
433435

434436
/* transform the list of arguments */
435437
foreach(args,c->args)
436438
{
437-
w=lfirst(args);
439+
CaseWhen*w= (CaseWhen*)lfirst(args);
440+
CaseWhen*neww=makeNode(CaseWhen);
441+
Node*warg;
442+
443+
Assert(IsA(w,CaseWhen));
444+
445+
warg=w->expr;
438446
if (c->arg!=NULL)
439447
{
440448
/* shorthand form was specified, so expand... */
@@ -443,81 +451,81 @@ transformExpr(ParseState *pstate, Node *expr, int precedence)
443451
a->oper=OP;
444452
a->opname="=";
445453
a->lexpr=c->arg;
446-
a->rexpr=w->expr;
447-
w->expr= (Node*)a;
454+
a->rexpr=warg;
455+
warg= (Node*)a;
448456
}
449-
lfirst(args)=transformExpr(pstate, (Node*)w,precedence);
450-
typeids=lappendi(typeids,exprType(w->result));
457+
neww->expr=transformExpr(pstate,warg,precedence);
458+
459+
if (!coerce_to_boolean(pstate,&neww->expr))
460+
elog(ERROR,"WHEN clause must have a boolean result");
461+
462+
/*
463+
* result is NULL for NULLIF() construct - thomas
464+
* 1998-11-11
465+
*/
466+
warg=w->result;
467+
if (warg==NULL)
468+
{
469+
A_Const*n=makeNode(A_Const);
470+
471+
n->val.type=T_Null;
472+
warg= (Node*)n;
473+
}
474+
neww->result=transformExpr(pstate,warg,precedence);
475+
476+
newargs=lappend(newargs,neww);
477+
typeids=lappendi(typeids,exprType(neww->result));
451478
}
452479

480+
newc->args=newargs;
481+
453482
/*
454483
* It's not shorthand anymore, so drop the implicit
455-
* argument. This is necessary to keep the executor from
456-
* seeing an untransformed expression... not to mention
457-
* keeping a re-application of transformExpr from doing
458-
* the wrong thing.
484+
* argument. This is necessary to keep any re-application
485+
* of transformExpr from doing the wrong thing.
459486
*/
460-
c->arg=NULL;
487+
newc->arg=NULL;
461488

462489
/* transform the default clause */
463-
if (c->defresult==NULL)
490+
defresult=c->defresult;
491+
if (defresult==NULL)
464492
{
465493
A_Const*n=makeNode(A_Const);
466494

467495
n->val.type=T_Null;
468-
c->defresult= (Node*)n;
496+
defresult= (Node*)n;
469497
}
470-
c->defresult=transformExpr(pstate,c->defresult,precedence);
498+
newc->defresult=transformExpr(pstate,defresult,precedence);
471499

472500
/*
473501
* Note: default result is considered the most significant
474502
* type in determining preferred type.This is how the
475503
* code worked before, but it seems a little bogus to me
476504
* --- tgl
477505
*/
478-
typeids=lconsi(exprType(c->defresult),typeids);
506+
typeids=lconsi(exprType(newc->defresult),typeids);
479507

480508
ptype=select_common_type(typeids,"CASE");
481-
c->casetype=ptype;
509+
newc->casetype=ptype;
482510

483511
/* Convert default result clause, if necessary */
484-
c->defresult=coerce_to_common_type(pstate,c->defresult,
485-
ptype,"CASE/ELSE");
512+
newc->defresult=coerce_to_common_type(pstate,
513+
newc->defresult,
514+
ptype,
515+
"CASE/ELSE");
486516

487517
/* Convert when-clause results, if necessary */
488-
foreach(args,c->args)
489-
{
490-
w=lfirst(args);
491-
w->result=coerce_to_common_type(pstate,w->result,
492-
ptype,"CASE/WHEN");
493-
}
494-
495-
result=expr;
496-
break;
497-
}
498-
499-
caseT_CaseWhen:
500-
{
501-
CaseWhen*w= (CaseWhen*)expr;
502-
503-
w->expr=transformExpr(pstate,w->expr,precedence);
504-
505-
if (!coerce_to_boolean(pstate,&w->expr))
506-
elog(ERROR,"WHEN clause must have a boolean result");
507-
508-
/*
509-
* result is NULL for NULLIF() construct - thomas
510-
* 1998-11-11
511-
*/
512-
if (w->result==NULL)
518+
foreach(args,newc->args)
513519
{
514-
A_Const*n=makeNode(A_Const);
520+
CaseWhen*w=(CaseWhen*)lfirst(args);
515521

516-
n->val.type=T_Null;
517-
w->result= (Node*)n;
522+
w->result=coerce_to_common_type(pstate,
523+
w->result,
524+
ptype,
525+
"CASE/WHEN");
518526
}
519-
w->result=transformExpr(pstate,w->result,precedence);
520-
result=expr;
527+
528+
result=(Node*)newc;
521529
break;
522530
}
523531

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