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Commit723476c

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Make a marginal performance improvement in predicate_implied_by and
predicate_refuted_by: if either top-level input is a single-element list,reduce it to its lone member before proceeding. This avoidsa useless level of AND-recursion within the recursive proof routines.It's worth doing because, for example, if the clause is a 100-elementlist and the predicate is a 1-element list then we'd otherwise stripthe predicate's list structure 100 times as we iterate through the clause.It's only needed at top level because there won't be any trivial ANDs belowthat --- this situation is an artifact of the decision to represent evensingle-item conditions as Lists in the "implicit AND" format, and that formatis only used at the top level of any predicate or restriction condition.
1 parent4db44b4 commit723476c

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1 file changed

+41
-7
lines changed

1 file changed

+41
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‎src/backend/optimizer/util/predtest.c‎

Lines changed: 41 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/optimizer/util/predtest.c,v 1.24 2009/01/09 15:46:10 tgl Exp $
12+
* $PostgreSQL: pgsql/src/backend/optimizer/util/predtest.c,v 1.25 2009/05/10 22:45:28 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -124,14 +124,31 @@ static void InvalidateOprProofCacheCallBack(Datum arg, int cacheid, ItemPointer
124124
bool
125125
predicate_implied_by(List*predicate_list,List*restrictinfo_list)
126126
{
127+
Node*p,
128+
*r;
129+
127130
if (predicate_list==NIL)
128131
return true;/* no predicate: implication is vacuous */
129132
if (restrictinfo_list==NIL)
130133
return false;/* no restriction: implication must fail */
131134

132-
/* Otherwise, away we go ... */
133-
returnpredicate_implied_by_recurse((Node*)restrictinfo_list,
134-
(Node*)predicate_list);
135+
/*
136+
* If either input is a single-element list, replace it with its lone
137+
* member; this avoids one useless level of AND-recursion. We only need
138+
* to worry about this at top level, since eval_const_expressions should
139+
* have gotten rid of any trivial ANDs or ORs below that.
140+
*/
141+
if (list_length(predicate_list)==1)
142+
p= (Node*)linitial(predicate_list);
143+
else
144+
p= (Node*)predicate_list;
145+
if (list_length(restrictinfo_list)==1)
146+
r= (Node*)linitial(restrictinfo_list);
147+
else
148+
r= (Node*)restrictinfo_list;
149+
150+
/* And away we go ... */
151+
returnpredicate_implied_by_recurse(r,p);
135152
}
136153

137154
/*
@@ -165,14 +182,31 @@ predicate_implied_by(List *predicate_list, List *restrictinfo_list)
165182
bool
166183
predicate_refuted_by(List*predicate_list,List*restrictinfo_list)
167184
{
185+
Node*p,
186+
*r;
187+
168188
if (predicate_list==NIL)
169189
return false;/* no predicate: no refutation is possible */
170190
if (restrictinfo_list==NIL)
171191
return false;/* no restriction: refutation must fail */
172192

173-
/* Otherwise, away we go ... */
174-
returnpredicate_refuted_by_recurse((Node*)restrictinfo_list,
175-
(Node*)predicate_list);
193+
/*
194+
* If either input is a single-element list, replace it with its lone
195+
* member; this avoids one useless level of AND-recursion. We only need
196+
* to worry about this at top level, since eval_const_expressions should
197+
* have gotten rid of any trivial ANDs or ORs below that.
198+
*/
199+
if (list_length(predicate_list)==1)
200+
p= (Node*)linitial(predicate_list);
201+
else
202+
p= (Node*)predicate_list;
203+
if (list_length(restrictinfo_list)==1)
204+
r= (Node*)linitial(restrictinfo_list);
205+
else
206+
r= (Node*)restrictinfo_list;
207+
208+
/* And away we go ... */
209+
returnpredicate_refuted_by_recurse(r,p);
176210
}
177211

178212
/*----------

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