Add system catalog columns pg_constraint.conindid and pg_trigger.tgconstrindid.

conindid is the index supporting a constraint.  We can use this not only for
unique/primary-key constraints, but also foreign-key constraints, which
depend on the unique index that constrains the referenced columns.
tgconstrindid is just copied from the constraint's conindid field, or is
zero for triggers not associated with constraints.

This is mainly intended as infrastructure for upcoming patches, but it has
some virtue in itself, since it exposes a relationship that you formerly
had to grovel in pg_depend to determine.  I simplified one information_schema
view accordingly.  (There is a pg_dump query that could also use conindid,
but I left it alone because it wasn't clear it'd get any faster.)

Author: tglsfdc

doc/src/sgml/catalogs.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.201 2009/07/01 23:57:33 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.202 2009/07/28 02:56:29 tgl Exp $ -->
 <!--
  Documentation of the system catalogs, directed toward PostgreSQL developers
  -->
@@ -1748,6 +1748,14 @@
       <entry>The domain this constraint is on; 0 if not a domain constraint</entry>
      </row>
 
+     <row>
+      <entry><structfield>conindid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
+      <entry>The index supporting this constraint, if it's a unique, primary
+       key, or foreign key constraint; else 0</entry>
+     </row>
+
      <row>
       <entry><structfield>confrelid</structfield></entry>
       <entry><type>oid</type></entry>
@@ -4510,6 +4518,13 @@
       <entry>The table referenced by a referential integrity constraint</entry>
      </row>
 
+     <row>
+      <entry><structfield>tgconstrindid</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry><literal><link linkend="catalog-pg-class"><structname>pg_class</structname></link>.oid</literal></entry>
+      <entry>The index supporting a unique, primary key, or referential integrity constraint</entry>
+     </row>
+
      <row>
       <entry><structfield>tgconstraint</structfield></entry>
       <entry><type>oid</type></entry>
@@ -4560,6 +4575,7 @@
     When <structfield>tgconstraint</> is nonzero,
     <structfield>tgisconstraint</> must be true, and
     <structfield>tgconstrname</>, <structfield>tgconstrrelid</>,
+    <structfield>tgconstrindid</>,
     <structfield>tgdeferrable</>, <structfield>tginitdeferred</> are redundant
     with the referenced <structname>pg_constraint</> entry.  The reason we
     keep these fields is that we support <quote>stand-alone</> constraint

doc/src/sgml/trigger.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/trigger.sgml,v 1.56 2009/05/27 01:18:06 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/trigger.sgml,v 1.57 2009/07/28 02:56:29 tgl Exp $ -->
 
  <chapter id="triggers">
   <title>Triggers</title>
@@ -486,6 +486,7 @@ typedef struct Trigger
     bool        tgenabled;
     bool        tgisconstraint;
     Oid         tgconstrrelid;
+    Oid         tgconstrindid;
     Oid         tgconstraint;
     bool        tgdeferrable;
     bool        tginitdeferred;
@@ -497,7 +498,7 @@ typedef struct Trigger
 </programlisting>
 
        where <structfield>tgname</> is the trigger's name,
-       <structfield>tgnargs</> is number of arguments in
+       <structfield>tgnargs</> is the number of arguments in
        <structfield>tgargs</>, and <structfield>tgargs</> is an array of
        pointers to the arguments specified in the <command>CREATE
        TRIGGER</command> statement. The other members are for internal use

src/backend/catalog/heap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.354 2009/06/11 14:48:54 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/heap.c,v 1.355 2009/07/28 02:56:29 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1659,6 +1659,7 @@ StoreRelCheck(Relation rel, char *ccname, Node *expr,
 						  attNos,		/* attrs in the constraint */
 						  keycount,		/* # attrs in the constraint */
 						  InvalidOid,	/* not a domain constraint */
+						  InvalidOid,	/* no associated index */
 						  InvalidOid,	/* Foreign key fields */
 						  NULL,
 						  NULL,
@@ -1668,7 +1669,6 @@ StoreRelCheck(Relation rel, char *ccname, Node *expr,
 						  ' ',
 						  ' ',
 						  ' ',
-						  InvalidOid,	/* no associated index */
 						  expr, /* Tree form check constraint */
 						  ccbin,	/* Binary form check constraint */
 						  ccsrc,	/* Source form check constraint */

src/backend/catalog/index.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.318 2009/06/11 14:48:55 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.319 2009/07/28 02:56:29 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -732,6 +732,7 @@ index_create(Oid heapRelationId,
 										   indexInfo->ii_KeyAttrNumbers,
 										   indexInfo->ii_NumIndexAttrs,
 										   InvalidOid,	/* no domain */
+										   indexRelationId,	/* index OID */
 										   InvalidOid,	/* no foreign key */
 										   NULL,
 										   NULL,
@@ -741,7 +742,6 @@ index_create(Oid heapRelationId,
 										   ' ',
 										   ' ',
 										   ' ',
-										   InvalidOid,	/* no associated index */
 										   NULL,		/* no check constraint */
 										   NULL,
 										   NULL,

src/backend/catalog/information_schema.sql

@@ -4,7 +4,7 @@
  *
  * Copyright (c) 2003-2009, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/catalog/information_schema.sql,v 1.57 2009/07/13 20:25:57 petere Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/information_schema.sql,v 1.58 2009/07/28 02:56:29 tgl Exp $
  */
 
 /*
@@ -44,17 +44,6 @@ CREATE FUNCTION _pg_keysequal(smallint[], smallint[]) RETURNS boolean
     LANGUAGE sql IMMUTABLE  -- intentionally not STRICT, to allow inlining
     AS 'select $1 <@ $2 and $2 <@ $1';
 
-/* Get the OID of the unique index that an FK constraint depends on */
-CREATE FUNCTION _pg_underlying_index(oid) RETURNS oid
-    LANGUAGE sql STRICT STABLE
-    AS $$
-SELECT refobjid FROM pg_catalog.pg_depend
-  WHERE classid = 'pg_catalog.pg_constraint'::pg_catalog.regclass AND
-        objid = $1 AND
-        refclassid = 'pg_catalog.pg_class'::pg_catalog.regclass AND
-        refobjsubid = 0 AND deptype = 'n'
-$$;
-
 /* Given an index's OID and an underlying-table column number, return the
  * column's position in the index (NULL if not there) */
 CREATE FUNCTION _pg_index_position(oid, smallint) RETURNS int
@@ -957,15 +946,15 @@ CREATE VIEW key_column_usage AS
            CAST(a.attname AS sql_identifier) AS column_name,
            CAST((ss.x).n AS cardinal_number) AS ordinal_position,
            CAST(CASE WHEN contype = 'f' THEN
-                  _pg_index_position(_pg_underlying_index(ss.coid),
-                                     ss.confkey[(ss.x).n])
+                       _pg_index_position(ss.conindid, ss.confkey[(ss.x).n])
                      ELSE NULL
                 END AS cardinal_number)
              AS position_in_unique_constraint
     FROM pg_attribute a,
          (SELECT r.oid AS roid, r.relname, r.relowner,
                  nc.nspname AS nc_nspname, nr.nspname AS nr_nspname,
-                 c.oid AS coid, c.conname, c.contype, c.confkey, c.confrelid,
+                 c.oid AS coid, c.conname, c.contype, c.conindid,
+                 c.confkey, c.confrelid,
                  _pg_expandarray(c.conkey) AS x
           FROM pg_namespace nr, pg_class r, pg_namespace nc,
                pg_constraint c

src/backend/catalog/pg_constraint.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/pg_constraint.c,v 1.46 2009/07/16 06:33:42 petere Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/pg_constraint.c,v 1.47 2009/07/28 02:56:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -49,6 +49,7 @@ CreateConstraintEntry(const char *constraintName,
 					  const int16 *constraintKey,
 					  int constraintNKeys,
 					  Oid domainId,
+					  Oid indexRelId,
 					  Oid foreignRelId,
 					  const int16 *foreignKey,
 					  const Oid *pfEqOp,
@@ -58,7 +59,6 @@ CreateConstraintEntry(const char *constraintName,
 					  char foreignUpdateType,
 					  char foreignDeleteType,
 					  char foreignMatchType,
-					  Oid indexRelId,
 					  Node *conExpr,
 					  const char *conBin,
 					  const char *conSrc,
@@ -144,6 +144,7 @@ CreateConstraintEntry(const char *constraintName,
 	values[Anum_pg_constraint_condeferred - 1] = BoolGetDatum(isDeferred);
 	values[Anum_pg_constraint_conrelid - 1] = ObjectIdGetDatum(relId);
 	values[Anum_pg_constraint_contypid - 1] = ObjectIdGetDatum(domainId);
+	values[Anum_pg_constraint_conindid - 1] = ObjectIdGetDatum(indexRelId);
 	values[Anum_pg_constraint_confrelid - 1] = ObjectIdGetDatum(foreignRelId);
 	values[Anum_pg_constraint_confupdtype - 1] = CharGetDatum(foreignUpdateType);
 	values[Anum_pg_constraint_confdeltype - 1] = CharGetDatum(foreignDeleteType);
@@ -273,11 +274,13 @@ CreateConstraintEntry(const char *constraintName,
 		}
 	}
 
-	if (OidIsValid(indexRelId))
+	if (OidIsValid(indexRelId) && constraintType == CONSTRAINT_FOREIGN)
 	{
 		/*
 		 * Register normal dependency on the unique index that supports a
-		 * foreign-key constraint.
+		 * foreign-key constraint.  (Note: for indexes associated with
+		 * unique or primary-key constraints, the dependency runs the other
+		 * way, and is not made here.)
 		 */
 		ObjectAddress relobject;
 

src/backend/commands/tablecmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.291 2009/07/20 02:42:27 adunstan Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.292 2009/07/28 02:56:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -152,6 +152,7 @@ typedef struct NewConstraint
 	char	   *name;			/* Constraint name, or NULL if none */
 	ConstrType	contype;		/* CHECK or FOREIGN */
 	Oid			refrelid;		/* PK rel, if FOREIGN */
+	Oid			refindid;		/* OID of PK's index, if FOREIGN */
 	Oid			conid;			/* OID of pg_constraint entry, if FOREIGN */
 	Node	   *qual;			/* Check expr or FkConstraint struct */
 	List	   *qualstate;		/* Execution state for CHECK */
@@ -247,9 +248,10 @@ static Oid transformFkeyCheckAttrs(Relation pkrel,
 						Oid *opclasses);
 static void checkFkeyPermissions(Relation rel, int16 *attnums, int natts);
 static void validateForeignKeyConstraint(FkConstraint *fkconstraint,
-							 Relation rel, Relation pkrel, Oid constraintOid);
+							 Relation rel, Relation pkrel,
+							 Oid pkindOid, Oid constraintOid);
 static void createForeignKeyTriggers(Relation rel, FkConstraint *fkconstraint,
-						 Oid constraintOid);
+						 Oid constraintOid, Oid indexOid);
 static void ATController(Relation rel, List *cmds, bool recurse);
 static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 		  bool recurse, bool recursing);
@@ -2915,6 +2917,7 @@ ATRewriteTables(List **wqueue)
 				refrel = heap_open(con->refrelid, RowShareLock);
 
 				validateForeignKeyConstraint(fkconstraint, rel, refrel,
+											 con->refindid,
 											 con->conid);
 
 				heap_close(refrel, NoLock);
@@ -4819,6 +4822,7 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 									  numfks,
 									  InvalidOid,		/* not a domain
 														 * constraint */
+									  indexOid,
 									  RelationGetRelid(pkrel),
 									  pkattnum,
 									  pfeqoperators,
@@ -4828,7 +4832,6 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 									  fkconstraint->fk_upd_action,
 									  fkconstraint->fk_del_action,
 									  fkconstraint->fk_matchtype,
-									  indexOid,
 									  NULL,		/* no check constraint */
 									  NULL,
 									  NULL,
@@ -4838,7 +4841,7 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 	/*
 	 * Create the triggers that will enforce the constraint.
 	 */
-	createForeignKeyTriggers(rel, fkconstraint, constrOid);
+	createForeignKeyTriggers(rel, fkconstraint, constrOid, indexOid);
 
 	/*
 	 * Tell Phase 3 to check that the constraint is satisfied by existing rows
@@ -4852,6 +4855,7 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 		newcon->name = fkconstraint->constr_name;
 		newcon->contype = CONSTR_FOREIGN;
 		newcon->refrelid = RelationGetRelid(pkrel);
+		newcon->refindid = indexOid;
 		newcon->conid = constrOid;
 		newcon->qual = (Node *) fkconstraint;
 
@@ -5141,6 +5145,7 @@ static void
 validateForeignKeyConstraint(FkConstraint *fkconstraint,
 							 Relation rel,
 							 Relation pkrel,
+							 Oid pkindOid,
 							 Oid constraintOid)
 {
 	HeapScanDesc scan;
@@ -5156,6 +5161,7 @@ validateForeignKeyConstraint(FkConstraint *fkconstraint,
 	trig.tgenabled = TRIGGER_FIRES_ON_ORIGIN;
 	trig.tgisconstraint = TRUE;
 	trig.tgconstrrelid = RelationGetRelid(pkrel);
+	trig.tgconstrindid = pkindOid;
 	trig.tgconstraint = constraintOid;
 	trig.tgdeferrable = FALSE;
 	trig.tginitdeferred = FALSE;
@@ -5209,7 +5215,7 @@ validateForeignKeyConstraint(FkConstraint *fkconstraint,
 
 static void
 CreateFKCheckTrigger(RangeVar *myRel, FkConstraint *fkconstraint,
-					 Oid constraintOid, bool on_insert)
+					 Oid constraintOid, Oid indexOid, bool on_insert)
 {
 	CreateTrigStmt *fk_trigger;
 
@@ -5237,7 +5243,7 @@ CreateFKCheckTrigger(RangeVar *myRel, FkConstraint *fkconstraint,
 	fk_trigger->constrrel = fkconstraint->pktable;
 	fk_trigger->args = NIL;
 
-	(void) CreateTrigger(fk_trigger, constraintOid, false);
+	(void) CreateTrigger(fk_trigger, constraintOid, indexOid, false);
 
 	/* Make changes-so-far visible */
 	CommandCounterIncrement();
@@ -5248,7 +5254,7 @@ CreateFKCheckTrigger(RangeVar *myRel, FkConstraint *fkconstraint,
  */
 static void
 createForeignKeyTriggers(Relation rel, FkConstraint *fkconstraint,
-						 Oid constraintOid)
+						 Oid constraintOid, Oid indexOid)
 {
 	RangeVar   *myRel;
 	CreateTrigStmt *fk_trigger;
@@ -5267,8 +5273,8 @@ createForeignKeyTriggers(Relation rel, FkConstraint *fkconstraint,
 	 * Build and execute a CREATE CONSTRAINT TRIGGER statement for the CHECK
 	 * action for both INSERTs and UPDATEs on the referencing table.
 	 */
-	CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, true);
-	CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, false);
+	CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, indexOid, true);
+	CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, indexOid, false);
 
 	/*
 	 * Build and execute a CREATE CONSTRAINT TRIGGER statement for the ON
@@ -5316,7 +5322,7 @@ createForeignKeyTriggers(Relation rel, FkConstraint *fkconstraint,
 	}
 	fk_trigger->args = NIL;
 
-	(void) CreateTrigger(fk_trigger, constraintOid, false);
+	(void) CreateTrigger(fk_trigger, constraintOid, indexOid, false);
 
 	/* Make changes-so-far visible */
 	CommandCounterIncrement();
@@ -5367,7 +5373,7 @@ createForeignKeyTriggers(Relation rel, FkConstraint *fkconstraint,
 	}
 	fk_trigger->args = NIL;
 
-	(void) CreateTrigger(fk_trigger, constraintOid, false);
+	(void) CreateTrigger(fk_trigger, constraintOid, indexOid, false);
 }
 
 /*