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.

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

2 files changed, 45 insertions, 12 deletions

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 3460fea56ba..130f7fc7c3f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -529,7 +529,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				columnref in_expr having_clause func_table xmltable array_expr
 				OptWhereClause operator_def_arg
 %type <list>	rowsfrom_item rowsfrom_list opt_col_def_list
-%type <boolean> opt_ordinality
+%type <boolean> opt_ordinality opt_without_overlaps
 %type <list>	ExclusionConstraintList ExclusionConstraintElem
 %type <list>	func_arg_list func_arg_list_opt
 %type <node>	func_arg_expr
@@ -4133,7 +4133,7 @@ ConstraintElem:
 					n->initially_valid = true;
 					$$ = (Node *) n;
 				}
-			| UNIQUE opt_unique_null_treatment '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
+			| UNIQUE opt_unique_null_treatment '(' columnList opt_without_overlaps ')' opt_c_include opt_definition OptConsTableSpace
 				ConstraintAttributeSpec
 				{
 					Constraint *n = makeNode(Constraint);
@@ -4142,11 +4142,12 @@ ConstraintElem:
 					n->location = @1;
 					n->nulls_not_distinct = !$2;
 					n->keys = $4;
-					n->including = $6;
-					n->options = $7;
+					n->without_overlaps = $5;
+					n->including = $7;
+					n->options = $8;
 					n->indexname = NULL;
-					n->indexspace = $8;
-					processCASbits($9, @9, "UNIQUE",
+					n->indexspace = $9;
+					processCASbits($10, @10, "UNIQUE",
 								   &n->deferrable, &n->initdeferred, NULL,
 								   NULL, yyscanner);
 					$$ = (Node *) n;
@@ -4167,7 +4168,7 @@ ConstraintElem:
 								   NULL, yyscanner);
 					$$ = (Node *) n;
 				}
-			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
+			| PRIMARY KEY '(' columnList opt_without_overlaps ')' opt_c_include opt_definition OptConsTableSpace
 				ConstraintAttributeSpec
 				{
 					Constraint *n = makeNode(Constraint);
@@ -4175,11 +4176,12 @@ ConstraintElem:
 					n->contype = CONSTR_PRIMARY;
 					n->location = @1;
 					n->keys = $4;
-					n->including = $6;
-					n->options = $7;
+					n->without_overlaps = $5;
+					n->including = $7;
+					n->options = $8;
 					n->indexname = NULL;
-					n->indexspace = $8;
-					processCASbits($9, @9, "PRIMARY KEY",
+					n->indexspace = $9;
+					processCASbits($10, @10, "PRIMARY KEY",
 								   &n->deferrable, &n->initdeferred, NULL,
 								   NULL, yyscanner);
 					$$ = (Node *) n;
@@ -4247,6 +4249,11 @@ opt_no_inherit:	NO INHERIT							{  $$ = true; }
 			| /* EMPTY */							{  $$ = false; }
 		;
 
+opt_without_overlaps:
+			WITHOUT OVERLAPS						{ $$ = true; }
+			| /*EMPTY*/								{ $$ = false; }
+	;
+
 opt_column_list:
 			'(' columnList ')'						{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index b2d1fa9d0d6..56ac4f516ea 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -1716,6 +1716,7 @@ generateClonedIndexStmt(RangeVar *heapRel, Relation source_idx,
 	index->unique = idxrec->indisunique;
 	index->nulls_not_distinct = idxrec->indnullsnotdistinct;
 	index->primary = idxrec->indisprimary;
+	index->iswithoutoverlaps = (idxrec->indisprimary || idxrec->indisunique) && idxrec->indisexclusion;
 	index->transformed = true;	/* don't need transformIndexStmt */
 	index->concurrent = false;
 	index->if_not_exists = false;
@@ -1765,7 +1766,9 @@ generateClonedIndexStmt(RangeVar *heapRel, Relation source_idx,
 				int			nElems;
 				int			i;
 
-				Assert(conrec->contype == CONSTRAINT_EXCLUSION);
+				Assert(conrec->contype == CONSTRAINT_EXCLUSION ||
+					   (index->iswithoutoverlaps &&
+						(conrec->contype == CONSTRAINT_PRIMARY || conrec->contype == CONSTRAINT_UNIQUE)));
 				/* Extract operator OIDs from the pg_constraint tuple */
 				datum = SysCacheGetAttrNotNull(CONSTROID, ht_constr,
 											   Anum_pg_constraint_conexclop);
@@ -2305,6 +2308,7 @@ transformIndexConstraint(Constraint *constraint, CreateStmtContext *cxt)
 	}
 	index->nulls_not_distinct = constraint->nulls_not_distinct;
 	index->isconstraint = true;
+	index->iswithoutoverlaps = constraint->without_overlaps;
 	index->deferrable = constraint->deferrable;
 	index->initdeferred = constraint->initdeferred;
 
@@ -2397,6 +2401,11 @@ transformIndexConstraint(Constraint *constraint, CreateStmtContext *cxt)
 					 errmsg("index \"%s\" is not valid", index_name),
 					 parser_errposition(cxt->pstate, constraint->location)));
 
+		/*
+		 * Today we forbid non-unique indexes, but we could permit GiST
+		 * indexes whose last entry is a range type and use that to create a
+		 * WITHOUT OVERLAPS constraint (i.e. a temporal constraint).
+		 */
 		if (!index_form->indisunique)
 			ereport(ERROR,
 					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -2673,6 +2682,23 @@ transformIndexConstraint(Constraint *constraint, CreateStmtContext *cxt)
 				notnullcmds = lappend(notnullcmds, notnullcmd);
 			}
 		}
+
+		if (constraint->without_overlaps)
+		{
+			/*
+			 * This enforces that there is at least one equality column
+			 * besides the WITHOUT OVERLAPS columns.  This is per SQL
+			 * standard.  XXX Do we need this?
+			 */
+			if (list_length(constraint->keys) < 2)
+				ereport(ERROR,
+						errcode(ERRCODE_SYNTAX_ERROR),
+						errmsg("constraint using WITHOUT OVERLAPS needs at least two columns"));
+
+			/* WITHOUT OVERLAPS requires a GiST index */
+			index->accessMethod = "gist";
+		}
+
 	}
 
 	/*