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Commit31d1f23

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Teach simplify_boolean_equality to simplify the forms foo <> true and
foo <> false, along with its previous duties of simplifying foo = trueand foo = false. (All of these are equivalent to just foo or NOT fooas the case may be.) It's not clear how often this is really useful;but it costs almost nothing to do, and it seems some people think weshould be smart about such cases. Per recent bug report.
1 parent400e2c9 commit31d1f23

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2 files changed

+42
-17
lines changed

2 files changed

+42
-17
lines changed

‎src/backend/optimizer/util/clauses.c

Lines changed: 40 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.277 2009/06/11 14:48:59 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.278 2009/07/20 00:24:30 tgl Exp $
1212
*
1313
* HISTORY
1414
* AUTHORDATEMAJOR EVENT
@@ -92,7 +92,7 @@ static List *simplify_or_arguments(List *args,
9292
staticList*simplify_and_arguments(List*args,
9393
eval_const_expressions_context*context,
9494
bool*haveNull,bool*forceFalse);
95-
staticExpr*simplify_boolean_equality(List*args);
95+
staticExpr*simplify_boolean_equality(Oidopno,List*args);
9696
staticExpr*simplify_function(Oidfuncid,
9797
Oidresult_type,int32result_typmod,List**args,
9898
boolallow_inline,
@@ -2186,12 +2186,14 @@ eval_const_expressions_mutator(Node *node,
21862186
return (Node*)simple;
21872187

21882188
/*
2189-
* If the operator is boolean equality, we know how to simplify cases
2190-
* involving one constant and one non-constant argument.
2189+
* If the operator is boolean equality or inequality, we know how to
2190+
* simplify cases involving one constant and one non-constant
2191+
* argument.
21912192
*/
2192-
if (expr->opno==BooleanEqualOperator)
2193+
if (expr->opno==BooleanEqualOperator||
2194+
expr->opno==BooleanNotEqualOperator)
21932195
{
2194-
simple=simplify_boolean_equality(args);
2196+
simple=simplify_boolean_equality(expr->opno,args);
21952197
if (simple)/* successfully simplified it */
21962198
return (Node*)simple;
21972199
}
@@ -3165,21 +3167,23 @@ simplify_and_arguments(List *args,
31653167

31663168
/*
31673169
* Subroutine for eval_const_expressions: try to simplify boolean equality
3170+
* or inequality condition
31683171
*
3169-
*Input is thelist of simplified arguments to the operator.
3172+
*Inputs are theoperator OID and the simplified arguments to the operator.
31703173
* Returns a simplified expression if successful, or NULL if cannot
31713174
* simplify the expression.
31723175
*
3173-
* The idea here is to reduce "x = true" to "x" and "x = false" to "NOT x".
3176+
* The idea here is to reduce "x = true" to "x" and "x = false" to "NOT x",
3177+
* or similarly "x <> true" to "NOT x" and "x <> false" to "x".
31743178
* This is only marginally useful in itself, but doing it in constant folding
3175-
* ensures that we will recognizethe two forms as being equivalent in, for
3179+
* ensures that we will recognizethese forms as being equivalent in, for
31763180
* example, partial index matching.
31773181
*
31783182
* We come here only if simplify_function has failed; therefore we cannot
31793183
* see two constant inputs, nor a constant-NULL input.
31803184
*/
31813185
staticExpr*
3182-
simplify_boolean_equality(List*args)
3186+
simplify_boolean_equality(Oidopno,List*args)
31833187
{
31843188
Expr*leftop;
31853189
Expr*rightop;
@@ -3190,18 +3194,38 @@ simplify_boolean_equality(List *args)
31903194
if (leftop&&IsA(leftop,Const))
31913195
{
31923196
Assert(!((Const*)leftop)->constisnull);
3193-
if (DatumGetBool(((Const*)leftop)->constvalue))
3194-
returnrightop;/* true = foo */
3197+
if (opno==BooleanEqualOperator)
3198+
{
3199+
if (DatumGetBool(((Const*)leftop)->constvalue))
3200+
returnrightop;/* true = foo */
3201+
else
3202+
returnmake_notclause(rightop);/* false = foo */
3203+
}
31953204
else
3196-
returnmake_notclause(rightop);/* false = foo */
3205+
{
3206+
if (DatumGetBool(((Const*)leftop)->constvalue))
3207+
returnmake_notclause(rightop);/* true <> foo */
3208+
else
3209+
returnrightop;/* false <> foo */
3210+
}
31973211
}
31983212
if (rightop&&IsA(rightop,Const))
31993213
{
32003214
Assert(!((Const*)rightop)->constisnull);
3201-
if (DatumGetBool(((Const*)rightop)->constvalue))
3202-
returnleftop;/* foo = true */
3215+
if (opno==BooleanEqualOperator)
3216+
{
3217+
if (DatumGetBool(((Const*)rightop)->constvalue))
3218+
returnleftop;/* foo = true */
3219+
else
3220+
returnmake_notclause(leftop);/* foo = false */
3221+
}
32033222
else
3204-
returnmake_notclause(leftop);/* foo = false */
3223+
{
3224+
if (DatumGetBool(((Const*)rightop)->constvalue))
3225+
returnmake_notclause(leftop);/* foo <> true */
3226+
else
3227+
returnleftop;/* foo <> false */
3228+
}
32053229
}
32063230
returnNULL;
32073231
}

‎src/include/catalog/pg_operator.h

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
99
* Portions Copyright (c) 1994, Regents of the University of California
1010
*
11-
* $PostgreSQL: pgsql/src/include/catalog/pg_operator.h,v 1.166 2009/06/11 14:49:09 momjian Exp $
11+
* $PostgreSQL: pgsql/src/include/catalog/pg_operator.h,v 1.167 2009/07/20 00:24:30 tgl Exp $
1212
*
1313
* NOTES
1414
* the genbki.sh script reads this file and generates .bki
@@ -93,6 +93,7 @@ DATA(insert OID = 82 ( ">=" PGNSP PGUID b f f232016 42037 int48ge scalar
9393
DATA(insertOID=58 ("<"PGNSPPGUIDbff161616591695boolltscalarltselscalarltjoinsel ));
9494
DATA(insertOID=59 (">"PGNSPPGUIDbff161616581694boolgtscalargtselscalargtjoinsel ));
9595
DATA(insertOID=85 ("<>"PGNSPPGUIDbff1616168591boolneneqselneqjoinsel ));
96+
#defineBooleanNotEqualOperator 85
9697
DATA(insertOID=91 ("="PGNSPPGUIDbtt1616169185booleqeqseleqjoinsel ));
9798
#defineBooleanEqualOperator 91
9899
DATA(insertOID=1694 ("<="PGNSPPGUIDbff161616169559boollescalarltselscalarltjoinsel ));

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