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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-23 00:43:39 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2011-10-23 00:43:39 -0400 |
| commit | 0f39d5050dc0dce99258381f33f1832c437aff85 (patch) | |
| tree | 90583250bd5cf7878686bad038ec74e9dd292744 /src/backend/optimizer/util/plancat.c | |
| parent | bb446b689b6681eb57a8a50605e119743190c4db (diff) | |
| download | postgresql-0f39d5050dc0dce99258381f33f1832c437aff85.tar.gz postgresql-0f39d5050dc0dce99258381f33f1832c437aff85.zip | |
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.
Diffstat (limited to 'src/backend/optimizer/util/plancat.c')
| -rw-r--r-- | src/backend/optimizer/util/plancat.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c index bb809522424..de629e93c9a 100644 --- a/src/backend/optimizer/util/plancat.c +++ b/src/backend/optimizer/util/plancat.c @@ -324,6 +324,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent, info->predOK = false; /* set later in indxpath.c */ info->unique = index->indisunique; + info->immediate = index->indimmediate; info->hypothetical = false; /* @@ -1076,6 +1077,11 @@ 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) |