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Commit0f39d50

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Don't trust deferred-unique indexes for join removal.
The uniqueness condition might fail to hold intra-transaction, and assumingit does can give incorrect query results. Per report from Marti Raudsepp,though this is not his proposed patch.Back-patch to 9.0, where both these features were introduced. In thereleased branches, add the new IndexOptInfo field to the end of the struct,to try to minimize ABI breakage for third-party code that may be examiningthat struct.
1 parentbb446b6 commit0f39d50

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5 files changed

+15
-4
lines changed

5 files changed

+15
-4
lines changed

‎src/backend/nodes/outfuncs.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1770,6 +1770,7 @@ _outIndexOptInfo(StringInfo str, IndexOptInfo *node)
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WRITE_NODE_FIELD(indextlist);
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WRITE_BOOL_FIELD(predOK);
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WRITE_BOOL_FIELD(unique);
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WRITE_BOOL_FIELD(immediate);
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WRITE_BOOL_FIELD(hypothetical);
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}
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‎src/backend/optimizer/path/indxpath.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2277,10 +2277,11 @@ relation_has_unique_index_for(PlannerInfo *root, RelOptInfo *rel,
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intc;
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/*
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* If the index is not unique orif it's a partial index that doesn't
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* match the query, it's useless here.
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* If the index is not unique, ornot immediately enforced, or if it's
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*a partial index that doesn'tmatch the query, it's useless here.
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*/
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if (!ind->unique|| (ind->indpred!=NIL&& !ind->predOK))
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if (!ind->unique|| !ind->immediate||
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(ind->indpred!=NIL&& !ind->predOK))
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continue;
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/*

‎src/backend/optimizer/util/plancat.c

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Original file line numberDiff line numberDiff line change
@@ -324,6 +324,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
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info->predOK= false;/* set later in indxpath.c */
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info->unique=index->indisunique;
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info->immediate=index->indimmediate;
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info->hypothetical= false;
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/*
@@ -1076,6 +1077,11 @@ join_selectivity(PlannerInfo *root,
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* Detect whether there is a unique index on the specified attribute
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* of the specified relation, thus allowing us to conclude that all
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* the (non-null) values of the attribute are distinct.
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*
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* This function does not check the index's indimmediate property, which
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* means that uniqueness may transiently fail to hold intra-transaction.
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* That's appropriate when we are making statistical estimates, but beware
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* of using this for any correctness proofs.
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*/
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bool
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has_unique_index(RelOptInfo*rel,AttrNumberattno)

‎src/backend/utils/adt/selfuncs.c

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4129,7 +4129,9 @@ get_join_variables(PlannerInfo *root, List *args, SpecialJoinInfo *sjinfo,
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*commonly the same as the exposed type of the variable argument,
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*but can be different in binary-compatible-type cases.
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*isunique: TRUE if we were able to match the var to a unique index,
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*implying its values are unique for this query.
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*implying its values are unique for this query. (Caution: this
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*should be trusted for statistical purposes only, since we do not
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*check indimmediate.)
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*
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* Caller is responsible for doing ReleaseVariableStats() before exiting.
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*/

‎src/include/nodes/relation.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -488,6 +488,7 @@ typedef struct IndexOptInfo
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boolpredOK;/* true if predicate matches query */
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boolunique;/* true if a unique index */
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boolimmediate;/* is uniqueness enforced immediately? */
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boolhypothetical;/* true if index doesn't really exist */
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boolamcanorderbyop;/* does AM support order by operator result? */
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boolamcanreturn;/* can AM return IndexTuples? */

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