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Commit4e89bae

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Revert the logic for expanding AND/OR conditions in pred_test() to what
it was in 7.4, and add some comments explaining why it has to be this way.I broke it for OR'd index predicates in a fit of code cleanup last summer.Per example from Sergey Koshcheyev.
1 parent5c4a91c commit4e89bae

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1 file changed

+69
-54
lines changed

1 file changed

+69
-54
lines changed

‎src/backend/optimizer/path/indxpath.c

Lines changed: 69 additions & 54 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.167 2004/12/31 22:00:04 pgsql Exp $
12+
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.168 2005/03/0100:24:52 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -64,9 +64,9 @@ static bool match_join_clause_to_indexcol(RelOptInfo *rel, IndexOptInfo *index,
6464
RestrictInfo*rinfo);
6565
staticOidindexable_operator(Expr*clause,Oidopclass,
6666
boolindexkey_on_left);
67-
staticboolpred_test_recurse_pred(Expr*predicate,List*restrictinfo_list);
6867
staticboolpred_test_restrict_list(Expr*predicate,List*restrictinfo_list);
6968
staticboolpred_test_recurse_restrict(Expr*predicate,Node*clause);
69+
staticboolpred_test_recurse_pred(Expr*predicate,Node*clause);
7070
staticboolpred_test_simple_clause(Expr*predicate,Node*clause);
7171
staticRelidsindexable_outerrelids(RelOptInfo*rel,IndexOptInfo*index);
7272
staticPath*make_innerjoin_index_path(Query*root,
@@ -749,11 +749,25 @@ check_partial_indexes(Query *root, RelOptInfo *rel)
749749
* Recursively checks whether the clauses in restrictinfo_list imply
750750
* that the given predicate is true.
751751
*
752-
* This routine (together with the routines it calls) first breaks down
753-
* the predicate to its constituent AND/OR elements, then similarly
754-
* breaks down the restriction clauses to AND/OR elements in an effort
755-
* to prove that each predicate element is implied. The top-level
756-
* List structure of each list corresponds to an AND list.
752+
* This routine (together with the routines it calls) iterates over
753+
* ANDs in the predicate first, then breaks down the restriction list
754+
* to its constituent AND/OR elements, and iterates over ORs
755+
* in the predicate last. This order is important to make the test
756+
* succeed whenever possible. --Nels, Jan '93
757+
*
758+
* For example, a restriction (a OR b) certainly implies a predicate
759+
* (a OR b OR c), but no one element of the predicate is individually
760+
* implied by the restriction. By expanding the predicate ORs last
761+
* we are able to prove that the whole predicate is implied by each arm
762+
* of the restriction. Conversely consider predicate (a AND b) with
763+
* restriction (a AND b AND c). This should be implied but we will
764+
* fail to prove it if we dissect the restriction first.
765+
*
766+
* The top-level List structure of each list corresponds to an AND list.
767+
* We assume that canonicalize_qual() has been applied and so there
768+
* are no explicit ANDs immediately below the top-level List structure.
769+
* (If this is not true we might fail to prove an implication that is
770+
* valid, but no worse consequences will ensue.)
757771
*/
758772
bool
759773
pred_test(List*predicate_list,List*restrictinfo_list)
@@ -779,65 +793,23 @@ pred_test(List *predicate_list, List *restrictinfo_list)
779793
return false;/* no restriction clauses: the test must
780794
* fail */
781795

796+
/* Take care of the AND semantics of the top-level predicate list */
782797
foreach(pred,predicate_list)
783798
{
784799
/*
785800
* if any clause is not implied, the whole predicate is not
786801
* implied.
787802
*/
788-
if (!pred_test_recurse_pred(lfirst(pred),restrictinfo_list))
803+
if (!pred_test_restrict_list(lfirst(pred),restrictinfo_list))
789804
return false;
790805
}
791806
return true;
792807
}
793808

794809

795-
/*
796-
* pred_test_recurse_pred
797-
* Does the "predicate inclusion test" for one conjunct of a predicate
798-
* expression. Here we recursively deal with the possibility that the
799-
* predicate conjunct is itself an AND or OR structure.
800-
*/
801-
staticbool
802-
pred_test_recurse_pred(Expr*predicate,List*restrictinfo_list)
803-
{
804-
List*items;
805-
ListCell*item;
806-
807-
Assert(predicate!=NULL);
808-
if (or_clause((Node*)predicate))
809-
{
810-
items= ((BoolExpr*)predicate)->args;
811-
foreach(item,items)
812-
{
813-
/* if any item is implied, the whole predicate is implied */
814-
if (pred_test_recurse_pred(lfirst(item),restrictinfo_list))
815-
return true;
816-
}
817-
return false;
818-
}
819-
elseif (and_clause((Node*)predicate))
820-
{
821-
items= ((BoolExpr*)predicate)->args;
822-
foreach(item,items)
823-
{
824-
/*
825-
* if any item is not implied, the whole predicate is not
826-
* implied
827-
*/
828-
if (!pred_test_recurse_pred(lfirst(item),restrictinfo_list))
829-
return false;
830-
}
831-
return true;
832-
}
833-
else
834-
returnpred_test_restrict_list(predicate,restrictinfo_list);
835-
}
836-
837-
838810
/*
839811
* pred_test_restrict_list
840-
* Does the "predicate inclusion test" for oneelement of a predicate
812+
* Does the "predicate inclusion test" for oneAND clause of a predicate
841813
* expression. Here we take care of the AND semantics of the top-level
842814
* restrictinfo list.
843815
*/
@@ -859,10 +831,10 @@ pred_test_restrict_list(Expr *predicate, List *restrictinfo_list)
859831

860832
/*
861833
* pred_test_recurse_restrict
862-
* Does the "predicate inclusion test" for oneelement of a predicate
834+
* Does the "predicate inclusion test" for oneAND clause of a predicate
863835
* expression. Here we recursively deal with the possibility that the
864836
* restriction-list element is itself an AND or OR structure; also,
865-
* we strip off RestrictInfo nodes to find barepredicate expressions.
837+
* we strip off RestrictInfo nodes to find barequalifier expressions.
866838
*/
867839
staticbool
868840
pred_test_recurse_restrict(Expr*predicate,Node*clause)
@@ -903,6 +875,49 @@ pred_test_recurse_restrict(Expr *predicate, Node *clause)
903875
}
904876
return false;
905877
}
878+
else
879+
returnpred_test_recurse_pred(predicate,clause);
880+
}
881+
882+
883+
/*
884+
* pred_test_recurse_pred
885+
* Does the "predicate inclusion test" for one conjunct of a predicate
886+
* expression. Here we recursively deal with the possibility that the
887+
* predicate conjunct is itself an AND or OR structure.
888+
*/
889+
staticbool
890+
pred_test_recurse_pred(Expr*predicate,Node*clause)
891+
{
892+
List*items;
893+
ListCell*item;
894+
895+
Assert(predicate!=NULL);
896+
if (or_clause((Node*)predicate))
897+
{
898+
items= ((BoolExpr*)predicate)->args;
899+
foreach(item,items)
900+
{
901+
/* if any item is implied, the whole predicate is implied */
902+
if (pred_test_recurse_pred(lfirst(item),clause))
903+
return true;
904+
}
905+
return false;
906+
}
907+
elseif (and_clause((Node*)predicate))
908+
{
909+
items= ((BoolExpr*)predicate)->args;
910+
foreach(item,items)
911+
{
912+
/*
913+
* if any item is not implied, the whole predicate is not
914+
* implied
915+
*/
916+
if (!pred_test_recurse_pred(lfirst(item),clause))
917+
return false;
918+
}
919+
return true;
920+
}
906921
else
907922
returnpred_test_simple_clause(predicate,clause);
908923
}

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