Apply fixes for problems with dropped columns whose types have also been

dropped.  Add regression test, too.

src/backend/catalog/heap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.232.2.1 2002/12/16 18:39:56 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.232.2.2 2003/05/12 00:17:33 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -75,7 +75,7 @@ static void StoreAttrDefault(Relation rel, AttrNumber attnum, char *adbin);
 static void StoreRelCheck(Relation rel, char *ccname, char *ccbin);
 static void StoreConstraints(Relation rel, TupleDesc tupdesc);
 static void SetRelationNumChecks(Relation rel, int numchecks);
-static void RemoveStatistics(Relation rel);
+static void RemoveStatistics(Relation rel, AttrNumber attnum);
 
 
 /* ----------------------------------------------------------------
@@ -911,8 +911,9 @@ DeleteAttributeTuples(Oid relid)
  *		RemoveAttributeById
  *
  * This is the guts of ALTER TABLE DROP COLUMN: actually mark the attribute
- * deleted in pg_attribute.  (Everything else needed, such as getting rid
+ * deleted in pg_attribute.  We also remove pg_statistic entries for it.
- * of any pg_attrdef entry, is handled by dependency.c.)
+ * (Everything else needed, such as getting rid of any pg_attrdef entry,
+ * is handled by dependency.c.)
  */
 void
 RemoveAttributeById(Oid relid, AttrNumber attnum)
@@ -946,6 +947,16 @@ RemoveAttributeById(Oid relid, AttrNumber attnum)
 	/* Mark the attribute as dropped */
 	attStruct->attisdropped = true;
 
+	/*
+	 * Set the type OID to invalid.  A dropped attribute's type link cannot
+	 * be relied on (once the attribute is dropped, the type might be too).
+	 * Fortunately we do not need the type row --- the only really essential
+	 * information is the type's typlen and typalign, which are preserved in
+	 * the attribute's attlen and attalign.  We set atttypid to zero here
+	 * as a means of catching code that incorrectly expects it to be valid.
+	 */
+	attStruct->atttypid = InvalidOid;
+
 	/* Remove any NOT NULL constraint the column may have */
 	attStruct->attnotnull = false;
 
@@ -969,6 +980,8 @@ RemoveAttributeById(Oid relid, AttrNumber attnum)
 
 	heap_close(attr_rel, RowExclusiveLock);
 
+	RemoveStatistics(rel, attnum);
+
 	relation_close(rel, NoLock);
 }
 
@@ -1143,7 +1156,7 @@ heap_drop_with_catalog(Oid rid)
 	/*
 	 * delete statistics
 	 */
-	RemoveStatistics(rel);
+	RemoveStatistics(rel, 0);
 
 	/*
 	 * delete attribute tuples
@@ -1817,27 +1830,45 @@ RemoveRelConstraints(Relation rel, const char *constrName,
 }
 
 
+/*
+ * RemoveStatistics --- remove entries in pg_statistic for a rel or column
+ *
+ * If attnum is zero, remove all entries for rel; else remove only the one
+ * for that column.
+ */
 static void
-RemoveStatistics(Relation rel)
+RemoveStatistics(Relation rel, AttrNumber attnum)
 {
 	Relation	pgstatistic;
 	SysScanDesc scan;
-	ScanKeyData key;
+	ScanKeyData key[2];
+	int			nkeys;
 	HeapTuple	tuple;
 
 	pgstatistic = heap_openr(StatisticRelationName, RowExclusiveLock);
 
-	ScanKeyEntryInitialize(&key, 0x0,
+	ScanKeyEntryInitialize(&key[0], 0x0,
 						   Anum_pg_statistic_starelid, F_OIDEQ,
 						   ObjectIdGetDatum(RelationGetRelid(rel)));
 
+	if (attnum == 0)
+		nkeys = 1;
+	else
+	{
+		ScanKeyEntryInitialize(&key[1], 0x0,
+							   Anum_pg_statistic_staattnum, F_INT2EQ,
+							   Int16GetDatum(attnum));
+		nkeys = 2;
+	}
+
 	scan = systable_beginscan(pgstatistic, StatisticRelidAttnumIndex, true,
-							  SnapshotNow, 1, &key);
+							  SnapshotNow, nkeys, key);
 
 	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
 		simple_heap_delete(pgstatistic, &tuple->t_self);
 
 	systable_endscan(scan);
+
 	heap_close(pgstatistic, RowExclusiveLock);
 }
 

src/backend/optimizer/prep/preptlist.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.57 2002/09/18 21:35:21 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.57.2.1 2003/05/12 00:17:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -171,6 +171,15 @@ expand_targetlist(List *tlist, int command_type,
 			 * the attribute, so that it gets copied to the new tuple. But
 			 * generate a NULL for dropped columns (we want to drop any
 			 * old values).
+			 *
+			 * When generating a NULL constant for a dropped column, we label
+			 * it INT4 (any other guaranteed-to-exist datatype would do as
+			 * well).  We can't label it with the dropped column's datatype
+			 * since that might not exist anymore.  It does not really
+			 * matter what we claim the type is, since NULL is NULL --- its
+			 * representation is datatype-independent.  This could perhaps
+			 * confuse code comparing the finished plan to the target
+			 * relation, however.
 			 */
 			Oid			atttype = att_tup->atttypid;
 			int32		atttypmod = att_tup->atttypmod;
@@ -179,6 +188,8 @@ expand_targetlist(List *tlist, int command_type,
 			switch (command_type)
 			{
 				case CMD_INSERT:
+					if (!att_tup->attisdropped)
+					{
 						new_expr = (Node *) makeConst(atttype,
 													  att_tup->attlen,
 													  (Datum) 0,
@@ -186,27 +197,48 @@ expand_targetlist(List *tlist, int command_type,
 													  att_tup->attbyval,
 													  false,	/* not a set */
 													  false);
-					if (!att_tup->attisdropped)
 						new_expr = coerce_type_constraints(new_expr,
 														   atttype,
 														   COERCE_IMPLICIT_CAST);
-					break;
+					}
-				case CMD_UPDATE:
+					else
-					/* Insert NULLs for dropped columns */
+					{
-					if (att_tup->attisdropped)
+						/* Insert NULL for dropped column */
-						new_expr = (Node *) makeConst(atttype,
+						new_expr = (Node *) makeConst(INT4OID,
-													  att_tup->attlen,
+													  sizeof(int32),
 													  (Datum) 0,
 													  true, /* isnull */
-													  att_tup->attbyval,
+													  true,	/* byval */
 													  false,	/* not a set */
 													  false);
-					else
+						/* label resdom with INT4, too */
+						atttype = INT4OID;
+						atttypmod = -1;
+					}
+					break;
+				case CMD_UPDATE:
+					if (!att_tup->attisdropped)
+					{
 						new_expr = (Node *) makeVar(result_relation,
 													attrno,
 													atttype,
 													atttypmod,
 													0);
+					}
+					else
+					{
+						/* Insert NULL for dropped column */
+						new_expr = (Node *) makeConst(INT4OID,
+													  sizeof(int32),
+													  (Datum) 0,
+													  true, /* isnull */
+													  true,	/* byval */
+													  false,	/* not a set */
+													  false);
+						/* label resdom with INT4, too */
+						atttype = INT4OID;
+						atttypmod = -1;
+					}
 					break;
 				default:
 					elog(ERROR, "expand_targetlist: unexpected command_type");

src/test/regress/expected/alter_table.out

@@ -1166,3 +1166,44 @@ order by relname, attnum;
 drop table p1, p2 cascade;
 NOTICE:  Drop cascades to table c1
 NOTICE:  Drop cascades to table gc1
+-- test that operations with a dropped column do not try to reference
+-- its datatype
+create domain mytype as text;
+create temp table foo (f1 text, f2 mytype, f3 text);
+insert into foo values('aa','bb','cc');
+select * from foo;
+ f1 | f2 | f3 
+----+----+----
+ aa | bb | cc
+(1 row)
+
+drop domain mytype cascade;
+NOTICE:  Drop cascades to table foo column f2
+select * from foo;
+ f1 | f3 
+----+----
+ aa | cc
+(1 row)
+
+insert into foo values('qq','rr');
+select * from foo;
+ f1 | f3 
+----+----
+ aa | cc
+ qq | rr
+(2 rows)
+
+update foo set f3 = 'zz';
+select * from foo;
+ f1 | f3 
+----+----
+ aa | zz
+ qq | zz
+(2 rows)
+
+select f3,max(f1) from foo group by f3;
+ f3 | max 
+----+-----
+ zz | qq
+(1 row)
+

src/test/regress/sql/alter_table.sql

@@ -845,3 +845,21 @@ where relname in ('p1','p2','c1','gc1') and attnum > 0 and not attisdropped
 order by relname, attnum;
 
 drop table p1, p2 cascade;
+
+-- test that operations with a dropped column do not try to reference
+-- its datatype
+
+create domain mytype as text;
+create temp table foo (f1 text, f2 mytype, f3 text);
+
+insert into foo values('aa','bb','cc');
+select * from foo;
+
+drop domain mytype cascade;
+
+select * from foo;
+insert into foo values('qq','rr');
+select * from foo;
+update foo set f3 = 'zz';
+select * from foo;
+select f3,max(f1) from foo group by f3;