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

dropped.  The simplest fix for INSERT/UPDATE cases turns out to be for
preptlist.c to insert NULLs of a known-good type (I used INT4) rather
than making them match the deleted column's type.  Since the representation
of NULL is actually datatype-independent, this should work fine.
I also re-reverted the patch to disable the use_physical_tlist optimization
in the presence of dropped columns.  It still doesn't look worth the
trouble to be smarter, if there are no other bugs to fix.
Added a regression test to catch future problems in this area.

Author: tglsfdc

src/backend/catalog/heap.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.243 2003/05/08 22:19:56 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.244 2003/05/12 00:17:02 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -76,7 +76,7 @@ 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);
 
 
 /* ----------------------------------------------------------------
@@ -925,8 +925,9 @@ 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
- * of any pg_attrdef entry, is handled by dependency.c.)
+ * deleted in pg_attribute.  We also remove pg_statistic entries for it.
+ * (Everything else needed, such as getting rid of any pg_attrdef entry,
+ * is handled by dependency.c.)
  */
 void
 RemoveAttributeById(Oid relid, AttrNumber attnum)
@@ -960,6 +961,16 @@ 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;
 
@@ -984,6 +995,8 @@ RemoveAttributeById(Oid relid, AttrNumber attnum)
 
 	heap_close(attr_rel, RowExclusiveLock);
 
+	RemoveStatistics(rel, attnum);
+
 	relation_close(rel, NoLock);
 }
 
@@ -1158,7 +1171,7 @@ heap_drop_with_catalog(Oid rid)
 	/*
 	 * delete statistics
 	 */
-	RemoveStatistics(rel);
+	RemoveStatistics(rel, 0);
 
 	/*
 	 * delete attribute tuples
@@ -1819,27 +1832,45 @@ 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/plan/createplan.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.141 2003/05/11 20:25:50 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/plan/createplan.c,v 1.142 2003/05/12 00:17:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -295,6 +295,12 @@ use_physical_tlist(RelOptInfo *rel)
 	 */
 	if (rel->reloptkind != RELOPT_BASEREL)
 		return false;
+	/*
+	 * Can't do it if relation contains dropped columns.  This is detected
+	 * in plancat.c, see notes there.
+	 */
+	if (rel->varlist == NIL)
+		return false;
 	/*
 	 * Can't do it if any system columns are requested, either.  (This could
 	 * possibly be fixed but would take some fragile assumptions in setrefs.c,

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 1.60 2003/02/03 21:15:44 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.61 2003/05/12 00:17:03 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;
@@ -179,31 +188,52 @@ expand_targetlist(List *tlist, int command_type,
 			switch (command_type)
 			{
 				case CMD_INSERT:
-					new_expr = (Node *) makeConst(atttype,
-												  att_tup->attlen,
-												  (Datum) 0,
-												  true, /* isnull */
-												  att_tup->attbyval);
 					if (!att_tup->attisdropped)
+					{
+						new_expr = (Node *) makeConst(atttype,
+													  att_tup->attlen,
+													  (Datum) 0,
+													  true, /* isnull */
+													  att_tup->attbyval);
 						new_expr = coerce_to_domain(new_expr,
 													InvalidOid,
 													atttype,
 													COERCE_IMPLICIT_CAST);
+					}
+					else
+					{
+						/* Insert NULL for dropped column */
+						new_expr = (Node *) makeConst(INT4OID,
+													  sizeof(int32),
+													  (Datum) 0,
+													  true, /* isnull */
+													  true /* byval */);
+						/* label resdom with INT4, too */
+						atttype = INT4OID;
+						atttypmod = -1;
+					}
 					break;
 				case CMD_UPDATE:
-					/* Insert NULLs for dropped columns */
-					if (att_tup->attisdropped)
-						new_expr = (Node *) makeConst(atttype,
-													  att_tup->attlen,
-													  (Datum) 0,
-													  true,		/* isnull */
-													  att_tup->attbyval);
-					else
+					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 */);
+						/* label resdom with INT4, too */
+						atttype = INT4OID;
+						atttypmod = -1;
+					}
 					break;
 				default:
 					elog(ERROR, "expand_targetlist: unexpected command_type");

src/backend/optimizer/util/plancat.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.81 2003/05/11 20:25:50 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.82 2003/05/12 00:17:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -62,15 +62,29 @@ get_relation_info(Oid relationObjectId, RelOptInfo *rel)
 	relation = heap_open(relationObjectId, AccessShareLock);
 
 	/*
-	 * Make list of physical Vars.  Note we do NOT ignore dropped columns;
-	 * the intent is to model the physical tuples of the relation.
+	 * Make list of physical Vars.  But if there are any dropped columns,
+	 * punt and set varlist to NIL.  (XXX Ideally we would like to include
+	 * dropped columns so that the varlist models the physical tuples
+	 * of the relation.  However this creates problems for ExecTypeFromTL,
+	 * which may be asked to build a tupdesc for a tlist that includes vars
+	 * of no-longer-existent types.  In theory we could dig out the required
+	 * info from the pg_attribute entries of the relation, but that data is
+	 * not readily available to ExecTypeFromTL.  For now, punt and don't
+	 * apply the physical-tlist optimization when there are dropped cols.)
 	 */
 	numattrs = RelationGetNumberOfAttributes(relation);
 
 	for (attrno = 1; attrno <= numattrs; attrno++)
 	{
 		Form_pg_attribute att_tup = relation->rd_att->attrs[attrno - 1];
 
+		if (att_tup->attisdropped)
+		{
+			/* found a dropped col, so punt */
+			varlist = NIL;
+			break;
+		}
+
 		varlist = lappend(varlist,
 						  makeVar(varno,
 								  attrno,

src/test/regress/expected/alter_table.out

@@ -1253,3 +1253,44 @@ select * from p1;
 drop table p1 cascade;
 NOTICE:  Drop cascades to table c1
 NOTICE:  Drop cascades to constraint p1_a1 on table c1
+-- 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

@@ -895,3 +895,21 @@ update p1 set a1 = a1 + 1, f2 = upper(f2);
 select * from p1;
 
 drop table p1 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;