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

3 files changed, 4 insertions, 1 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 516b9487435..88467977f89 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -204,6 +204,7 @@ typedef struct IndexInfo
 	bool		ii_Concurrent;
 	bool		ii_BrokenHotChain;
 	bool		ii_Summarizing;
+	bool		ii_WithoutOverlaps;
 	int			ii_ParallelWorkers;
 	Oid			ii_Am;
 	void	   *ii_AmCache;
diff --git a/src/include/nodes/makefuncs.h b/src/include/nodes/makefuncs.h
index 5209d3de89c..0765e5c57b4 100644
--- a/src/include/nodes/makefuncs.h
+++ b/src/include/nodes/makefuncs.h
@@ -98,7 +98,7 @@ extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
 								List *expressions, List *predicates,
 								bool unique, bool nulls_not_distinct,
 								bool isready, bool concurrent,
-								bool summarizing);
+								bool summarizing, bool withoutoverlaps);
 
 extern Node *makeStringConst(char *str, int location);
 extern DefElem *makeDefElem(char *name, Node *arg, int location);
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index d6f7e795fe1..7e58db25268 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2744,6 +2744,7 @@ typedef struct Constraint
 	bool		nulls_not_distinct; /* null treatment for UNIQUE constraints */
 	List	   *keys;			/* String nodes naming referenced key
 								 * column(s); for UNIQUE/PK/NOT NULL */
+	bool		without_overlaps;	/* WITHOUT OVERLAPS specified */
 	List	   *including;		/* String nodes naming referenced nonkey
 								 * column(s); for UNIQUE/PK */
 	List	   *exclusions;		/* list of (IndexElem, operator name) pairs;
@@ -3367,6 +3368,7 @@ typedef struct IndexStmt
 	bool		nulls_not_distinct; /* null treatment for UNIQUE constraints */
 	bool		primary;		/* is index a primary key? */
 	bool		isconstraint;	/* is it for a pkey/unique constraint? */
+	bool		iswithoutoverlaps;	/* is the constraint WITHOUT OVERLAPS? */
 	bool		deferrable;		/* is the constraint DEFERRABLE? */
 	bool		initdeferred;	/* is the constraint INITIALLY DEFERRED? */
 	bool		transformed;	/* true when transformIndexStmt is finished */