Add temporal PRIMARY KEY and UNIQUE constraints

Add WITHOUT OVERLAPS clause to PRIMARY KEY and UNIQUE constraints.
These are backed by GiST indexes instead of B-tree indexes, since they
are essentially exclusion constraints with = for the scalar parts of
the key and && for the temporal part.

(previously committed as 46a0cd4cefb, reverted by 46a0cd4cefb; the new
part is this:)

Because 'empty' && 'empty' is false, the temporal PK/UQ constraint
allowed duplicates, which is confusing to users and breaks internal
expectations.  For instance, when GROUP BY checks functional
dependencies on the PK, it allows selecting other columns from the
table, but in the presence of duplicate keys you could get the value
from any of their rows.  So we need to forbid empties.

This all means that at the moment we can only support ranges and
multiranges for temporal PK/UQs, unlike the original patch (above).
Documentation and tests for this are added.  But this could
conceivably be extended by introducing some more general support for
the notion of "empty" for other types.

Author: Paul A. Jungwirth <[email protected]>
Reviewed-by: Peter Eisentraut <[email protected]>
Reviewed-by: jian he <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com

1 files changed, 10 insertions, 4 deletions

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 33759056e37..b2b3ecb5244 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -1394,7 +1394,8 @@ index_concurrently_create_copy(Relation heapRelation, Oid oldIndexId,
 							oldInfo->ii_NullsNotDistinct,
 							false,	/* not ready for inserts */
 							true,
-							indexRelation->rd_indam->amsummarizing);
+							indexRelation->rd_indam->amsummarizing,
+							oldInfo->ii_WithoutOverlaps);
 
 	/*
 	 * Extract the list of column names and the column numbers for the new
@@ -1874,6 +1875,7 @@ index_concurrently_set_dead(Oid heapId, Oid indexId)
  *		INDEX_CONSTR_CREATE_UPDATE_INDEX: update the pg_index row
  *		INDEX_CONSTR_CREATE_REMOVE_OLD_DEPS: remove existing dependencies
  *			of index on table's columns
+ *		INDEX_CONSTR_CREATE_WITHOUT_OVERLAPS: constraint uses WITHOUT OVERLAPS
  * allow_system_table_mods: allow table to be a system catalog
  * is_internal: index is constructed due to internal process
  */
@@ -1897,11 +1899,13 @@ index_constraint_create(Relation heapRelation,
 	bool		mark_as_primary;
 	bool		islocal;
 	bool		noinherit;
+	bool		is_without_overlaps;
 	int			inhcount;
 
 	deferrable = (constr_flags & INDEX_CONSTR_CREATE_DEFERRABLE) != 0;
 	initdeferred = (constr_flags & INDEX_CONSTR_CREATE_INIT_DEFERRED) != 0;
 	mark_as_primary = (constr_flags & INDEX_CONSTR_CREATE_MARK_AS_PRIMARY) != 0;
+	is_without_overlaps = (constr_flags & INDEX_CONSTR_CREATE_WITHOUT_OVERLAPS) != 0;
 
 	/* constraint creation support doesn't work while bootstrapping */
 	Assert(!IsBootstrapProcessingMode());
@@ -1978,6 +1982,7 @@ index_constraint_create(Relation heapRelation,
 								   islocal,
 								   inhcount,
 								   noinherit,
+								   is_without_overlaps,
 								   is_internal);
 
 	/*
@@ -2427,7 +2432,8 @@ BuildIndexInfo(Relation index)
 					   indexStruct->indnullsnotdistinct,
 					   indexStruct->indisready,
 					   false,
-					   index->rd_indam->amsummarizing);
+					   index->rd_indam->amsummarizing,
+					   indexStruct->indisexclusion && indexStruct->indisunique);
 
 	/* fill in attribute numbers */
 	for (i = 0; i < numAtts; i++)
@@ -2486,7 +2492,8 @@ BuildDummyIndexInfo(Relation index)
 					   indexStruct->indnullsnotdistinct,
 					   indexStruct->indisready,
 					   false,
-					   index->rd_indam->amsummarizing);
+					   index->rd_indam->amsummarizing,
+					   indexStruct->indisexclusion && indexStruct->indisunique);
 
 	/* fill in attribute numbers */
 	for (i = 0; i < numAtts; i++)
@@ -3224,7 +3231,6 @@ IndexCheckExclusion(Relation heapRelation,
 	indexInfo->ii_PredicateState = NULL;
 }
 
-
 /*
  * validate_index - support code for concurrent index builds
  *