From Stephan Szabo:

I believe this should fix the issue that Philip Warner
noticed about the check for unique constraints meeting the
referenced keys of a foreign key constraint allowing the
specification of a subset of a foreign key instead of
rejecting it.  I also added tests for a base case of
this to the foreign key and alter table tests and patches
for expected output.

src/backend/commands/command.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.112 2000/11/16 22:30:19 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.113 2000/12/05 19:57:55 tgl Exp $
  *
  * NOTES
  *	  The PerformAddAttribute() code, like most of the relation
@@ -1287,6 +1287,12 @@ AlterTableAddConstraint(char *relationName,
 				{
 					List	   *attrl;
 
+					/* Make sure this index has the same number of keys -- It obviously
+					 * won't match otherwise. */
+					for (i = 0; i < INDEX_MAX_KEYS && indexStruct->indkey[i] != 0; i++);
+					if (i!=length(fkconstraint->pk_attrs))
+						found=false;
+					else {
 						/* go through the fkconstraint->pk_attrs list */
 						foreach(attrl, fkconstraint->pk_attrs)
 						{
@@ -1309,6 +1315,7 @@ AlterTableAddConstraint(char *relationName,
 								break;
 						}
 					}
+				}
 				ReleaseSysCache(indexTuple);
 				if (found)
 					break;

src/backend/parser/analyze.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$Id: analyze.c,v 1.169 2000/12/05 19:15:10 tgl Exp $
+ *	$Id: analyze.c,v 1.170 2000/12/05 19:57:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1209,6 +1209,13 @@ transformCreateStmt(ParseState *pstate, CreateStmt *stmt)
 						List *pkattrs;
 						Ident *pkattr;
 						if (ind->unique) {
+							int count=0;
+							foreach(indparms, ind->indexParams) {
+								count++;
+							}
+							if (count!=length(fkconstraint->pk_attrs))
+								found=0;
+							else {
 								foreach(pkattrs, fkconstraint->pk_attrs) {
 									found=0;
 									pkattr=lfirst(pkattrs);
@@ -1223,6 +1230,7 @@ transformCreateStmt(ParseState *pstate, CreateStmt *stmt)
 										break;
 								}
 							}
+						}
 						if (found)
 							break;
 					}
@@ -2634,6 +2642,10 @@ transformFkeyCheckAttrs(FkConstraint *fkconstraint)
 		{
 			List *attrl;
 
+			for (i = 0; i < INDEX_MAX_KEYS && indexStruct->indkey[i] != 0; i++);
+			if (i!=length(fkconstraint->pk_attrs))
+				found=false;
+			else {
 				/* go through the fkconstraint->pk_attrs list */
 				foreach(attrl, fkconstraint->pk_attrs)
 				{
@@ -2656,6 +2668,7 @@ transformFkeyCheckAttrs(FkConstraint *fkconstraint)
 						break;
 				}
 			}
+		}
 		ReleaseSysCache(indexTuple);
 		if (found)
 			break;		

src/test/regress/expected/alter_table.out

@@ -273,6 +273,9 @@ SELECT unique1 FROM tenk1 WHERE unique1 < 5;
 CREATE TABLE tmp2 (a int primary key);
 NOTICE:  CREATE TABLE/PRIMARY KEY will create implicit index 'tmp2_pkey' for table 'tmp2'
 CREATE TABLE tmp3 (a int, b int);
+CREATE TABLE tmp4 (a int, b int, unique(a,b));
+NOTICE:  CREATE TABLE/UNIQUE will create implicit index 'tmp4_a_key' for table 'tmp4'
+CREATE TABLE tmp5 (a int, b int);
 -- Insert rows into tmp2 (pktable)
 INSERT INTO tmp2 values (1);
 INSERT INTO tmp2 values (2);
@@ -299,6 +302,13 @@ DELETE FROM tmp3 where a=5;
 -- Try (and succeed)
 ALTER TABLE tmp3 add constraint tmpconstr foreign key (a) references tmp2 match full;
 NOTICE:  ALTER TABLE ... ADD CONSTRAINT will create implicit trigger(s) for FOREIGN KEY check(s)
+-- Try (and fail) to create constraint from tmp5(a) to tmp4(a) - unique constraint on
+-- tmp4 is a,b
+ALTER TABLE tmp5 add constraint tmpconstr foreign key(a) references tmp4(a) match full;
+NOTICE:  ALTER TABLE ... ADD CONSTRAINT will create implicit trigger(s) for FOREIGN KEY check(s)
+ERROR:  UNIQUE constraint matching given keys for referenced table "tmp4" not found
+DROP TABLE tmp5;
+DROP TABLE tmp4;
 DROP TABLE tmp3;
 NOTICE:  DROP TABLE implicitly drops referential integrity trigger from table "tmp2"
 NOTICE:  DROP TABLE implicitly drops referential integrity trigger from table "tmp2"

src/test/regress/expected/foreign_key.out

@@ -703,3 +703,12 @@ ERROR:  table "fktable_fail1" does not exist
 DROP TABLE FKTABLE_FAIL2;
 ERROR:  table "fktable_fail2" does not exist
 DROP TABLE PKTABLE;
+-- Test for referencing column number smaller than referenced constraint
+CREATE TABLE PKTABLE (ptest1 int, ptest2 int, UNIQUE(ptest1, ptest2));
+NOTICE:  CREATE TABLE/UNIQUE will create implicit index 'pktable_ptest1_key' for table 'pktable'
+CREATE TABLE FKTABLE_FAIL1 (ftest1 int REFERENCES pktable(ptest1));
+NOTICE:  CREATE TABLE will create implicit trigger(s) for FOREIGN KEY check(s)
+ERROR:  UNIQUE constraint matching given keys for referenced table "pktable" not found
+DROP TABLE FKTABLE_FAIL1;
+ERROR:  table "fktable_fail1" does not exist
+DROP TABLE PKTABLE;

src/test/regress/sql/alter_table.sql

@@ -169,6 +169,10 @@ CREATE TABLE tmp2 (a int primary key);
 
 CREATE TABLE tmp3 (a int, b int);
 
+CREATE TABLE tmp4 (a int, b int, unique(a,b));
+
+CREATE TABLE tmp5 (a int, b int);
+
 -- Insert rows into tmp2 (pktable)
 INSERT INTO tmp2 values (1);
 INSERT INTO tmp2 values (2);
@@ -195,6 +199,15 @@ DELETE FROM tmp3 where a=5;
 -- Try (and succeed)
 ALTER TABLE tmp3 add constraint tmpconstr foreign key (a) references tmp2 match full;
 
+-- Try (and fail) to create constraint from tmp5(a) to tmp4(a) - unique constraint on
+-- tmp4 is a,b
+
+ALTER TABLE tmp5 add constraint tmpconstr foreign key(a) references tmp4(a) match full;
+
+DROP TABLE tmp5;
+
+DROP TABLE tmp4;
+
 DROP TABLE tmp3;
 
 DROP TABLE tmp2;

src/test/regress/sql/foreign_key.sql

@@ -418,3 +418,10 @@ CREATE TABLE FKTABLE_FAIL2 ( ftest1 int, CONSTRAINT fkfail1 FOREIGN KEY (ftest1)
 DROP TABLE FKTABLE_FAIL1;
 DROP TABLE FKTABLE_FAIL2;
 DROP TABLE PKTABLE;
+
+-- Test for referencing column number smaller than referenced constraint
+CREATE TABLE PKTABLE (ptest1 int, ptest2 int, UNIQUE(ptest1, ptest2));
+CREATE TABLE FKTABLE_FAIL1 (ftest1 int REFERENCES pktable(ptest1));
+
+DROP TABLE FKTABLE_FAIL1;
+DROP TABLE PKTABLE;