From 9fbb3edff085f2f004c24b988b43c7cd4f132e2f Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sun, 23 Oct 2011 00:43:52 -0400 Subject: [PATCH] Don't trust deferred-unique indexes for join removal. The uniqueness condition might fail to hold intra-transaction, and assuming it 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 the released 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 examining that struct. --- src/backend/nodes/outfuncs.c | 1 + src/backend/optimizer/path/indxpath.c | 7 ++++--- src/backend/optimizer/util/plancat.c | 6 ++++++ src/backend/utils/adt/selfuncs.c | 4 +++- src/include/nodes/relation.h | 2 ++ 5 files changed, 16 insertions(+), 4 deletions(-) diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c index 09dc9ccb5e..5c56658a27 100644 --- a/src/backend/nodes/outfuncs.c +++ b/src/backend/nodes/outfuncs.c @@ -1616,6 +1616,7 @@ _outIndexOptInfo(StringInfo str, IndexOptInfo *node) WRITE_NODE_FIELD(indpred); WRITE_BOOL_FIELD(predOK); WRITE_BOOL_FIELD(unique); + WRITE_BOOL_FIELD(immediate); WRITE_BOOL_FIELD(hypothetical); } diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c index 2c97bea3fa..e43e12d883 100644 --- a/src/backend/optimizer/path/indxpath.c +++ b/src/backend/optimizer/path/indxpath.c @@ -1948,10 +1948,11 @@ relation_has_unique_index_for(PlannerInfo *root, RelOptInfo *rel, int c; /* - * If the index is not unique or if it's a partial index that doesn't - * match the query, it's useless here. + * If the index is not unique, or not immediately enforced, or if it's + * a partial index that doesn't match the query, it's useless here. */ - if (!ind->unique || (ind->indpred != NIL && !ind->predOK)) + if (!ind->unique || !ind->immediate || + (ind->indpred != NIL && !ind->predOK)) continue; /* diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c index e35c8c326d..f7fb38404f 100644 --- a/src/backend/optimizer/util/plancat.c +++ b/src/backend/optimizer/util/plancat.c @@ -275,6 +275,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent, ChangeVarNodes((Node *) info->indpred, 1, varno, 0); info->predOK = false; /* set later in indxpath.c */ info->unique = index->indisunique; + info->immediate = index->indimmediate; info->hypothetical = false; /* @@ -876,6 +877,11 @@ join_selectivity(PlannerInfo *root, * Detect whether there is a unique index on the specified attribute * of the specified relation, thus allowing us to conclude that all * the (non-null) values of the attribute are distinct. + * + * This function does not check the index's indimmediate property, which + * means that uniqueness may transiently fail to hold intra-transaction. + * That's appropriate when we are making statistical estimates, but beware + * of using this for any correctness proofs. */ bool has_unique_index(RelOptInfo *rel, AttrNumber attno) diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index 7c1567a2cc..6989627adc 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -4102,7 +4102,9 @@ get_join_variables(PlannerInfo *root, List *args, SpecialJoinInfo *sjinfo, * commonly the same as the exposed type of the variable argument, * but can be different in binary-compatible-type cases. * isunique: TRUE if we were able to match the var to a unique index, - * implying its values are unique for this query. + * implying its values are unique for this query. (Caution: this + * should be trusted for statistical purposes only, since we do not + * check indimmediate.) * * Caller is responsible for doing ReleaseVariableStats() before exiting. */ diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index 7d39e10747..dc3a37eae9 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -473,6 +473,8 @@ typedef struct IndexOptInfo bool amhasgetbitmap; /* does AM have amgetbitmap interface? */ /* added in 9.0.4: */ bool hypothetical; /* true if index doesn't really exist */ + /* added in 9.0.6: */ + bool immediate; /* is uniqueness enforced immediately? */ } IndexOptInfo; -- 2.40.0