Fix new RI operator selection code to do the right thing when working with

an opclass for a generic type such as ANYARRAY.  The original coding failed
to check that PK and FK columns were of the same array type.  Per discussion
with Tom Dunstan.  Also, make the code a shade more readable by not trying
to economize on variables.

src/backend/commands/tablecmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.214 2007/02/14 01:58:56 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.215 2007/02/16 22:04:02 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3943,11 +3943,10 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 	/*
 	 * Look up the equality operators to use in the constraint.
 	 *
-	 * Note that we look for operator(s) with the PK type on the left; when
-	 * the types are different this is the right choice because the PK index
-	 * will need operators with the indexkey on the left.  Also, we take the
-	 * PK type as being the declared input type of the opclass, which might be
-	 * binary-compatible but not identical to the PK column type.
+	 * Note that we have to be careful about the difference between the actual
+	 * PK column type and the opclass' declared input type, which might be
+	 * only binary-compatible with it.  The declared opcintype is the right
+	 * thing to probe pg_amop with.
 	 */
 	if (numfks != numpks)
 		ereport(ERROR,
@@ -3956,12 +3955,14 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 
 	for (i = 0; i < numpks; i++)
 	{
+		Oid			pktype = pktypoid[i];
+		Oid			fktype = fktypoid[i];
+		Oid			fktyped;
 		HeapTuple	cla_ht;
 		Form_pg_opclass cla_tup;
 		Oid			amid;
 		Oid			opfamily;
-		Oid			pktype;
-		Oid			fktype;
+		Oid			opcintype;
 		Oid			pfeqop;
 		Oid			ppeqop;
 		Oid			ffeqop;
@@ -3976,7 +3977,7 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 		cla_tup = (Form_pg_opclass) GETSTRUCT(cla_ht);
 		amid = cla_tup->opcmethod;
 		opfamily = cla_tup->opcfamily;
-		pktype = cla_tup->opcintype;
+		opcintype = cla_tup->opcintype;
 		ReleaseSysCache(cla_ht);
 
 		/*
@@ -3991,30 +3992,50 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 		eqstrategy = BTEqualStrategyNumber;
 
 		/*
-		 * There had better be a PK = PK operator for the index.
+		 * There had better be a primary equality operator for the index.
+		 * We'll use it for PK = PK comparisons.
 		 */
-		ppeqop = get_opfamily_member(opfamily, pktype, pktype, eqstrategy);
+		ppeqop = get_opfamily_member(opfamily, opcintype, opcintype,
+									 eqstrategy);
 
 		if (!OidIsValid(ppeqop))
 			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
-				 eqstrategy, pktype, pktype, opfamily);
+				 eqstrategy, opcintype, opcintype, opfamily);
 
 		/*
 		 * Are there equality operators that take exactly the FK type?
 		 * Assume we should look through any domain here.
 		 */
-		fktype = getBaseType(fktypoid[i]);
+		fktyped = getBaseType(fktype);
 
-		pfeqop = get_opfamily_member(opfamily, pktype, fktype, eqstrategy);
-		ffeqop = get_opfamily_member(opfamily, fktype, fktype, eqstrategy);
+		pfeqop = get_opfamily_member(opfamily, opcintype, fktyped,
+									 eqstrategy);
+		if (OidIsValid(pfeqop))
+			ffeqop = get_opfamily_member(opfamily, fktyped, fktyped,
+										 eqstrategy);
+		else
+			ffeqop = InvalidOid;				/* keep compiler quiet */
 
 		if (!(OidIsValid(pfeqop) && OidIsValid(ffeqop)))
 		{
 			/*
 			 * Otherwise, look for an implicit cast from the FK type to
-			 * the PK type, and if found, use the PK type's equality operator.
+			 * the opcintype, and if found, use the primary equality operator.
+			 * This is a bit tricky because opcintype might be a generic type
+			 * such as ANYARRAY, and so what we have to test is whether the
+			 * two actual column types can be concurrently cast to that type.
+			 * (Otherwise, we'd fail to reject combinations such as int[] and
+			 * point[].)
 			 */
-			if (can_coerce_type(1, &fktype, &pktype, COERCION_IMPLICIT))
+			Oid		input_typeids[2];
+			Oid		target_typeids[2];
+
+			input_typeids[0] = pktype;
+			input_typeids[1] = fktype;
+			target_typeids[0] = opcintype;
+			target_typeids[1] = opcintype;
+			if (can_coerce_type(2, input_typeids, target_typeids,
+								COERCION_IMPLICIT))
 				pfeqop = ffeqop = ppeqop;
 		}
 
@@ -4028,8 +4049,8 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 							   "are of incompatible types: %s and %s.",
 							   strVal(list_nth(fkconstraint->fk_attrs, i)),
 							   strVal(list_nth(fkconstraint->pk_attrs, i)),
-							   format_type_be(fktypoid[i]),
-							   format_type_be(pktypoid[i]))));
+							   format_type_be(fktype),
+							   format_type_be(pktype))));
 
 		pfeqoperators[i] = pfeqop;
 		ppeqoperators[i] = ppeqop;