Trial implementation of ALTER DROP COLUMN.

They are #ifdef'd.
Add -D_DROP_COLUMN_HACK__ compile option
to evaluate it.

src/backend/commands/copy.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.101 2000/02/13 18:59:50 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.102 2000/03/09 05:00:23 inoue Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -394,6 +394,9 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
 
 	int32		attr_count,
 				i;
+#ifdef	_DROP_COLUMN_HACK__
+	bool		*valid;
+#endif /* _DROP_COLUMN_HACK__ */
 	Form_pg_attribute *attr;
 	FmgrInfo   *out_functions;
 	Oid			out_func_oid;
@@ -425,8 +428,20 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
 		out_functions = (FmgrInfo *) palloc(attr_count * sizeof(FmgrInfo));
 		elements = (Oid *) palloc(attr_count * sizeof(Oid));
 		typmod = (int32 *) palloc(attr_count * sizeof(int32));
+#ifdef	_DROP_COLUMN_HACK__
+		valid = (bool *) palloc(attr_count * sizeof(bool));
+#endif /* _DROP_COLUMN_HACK__ */
 		for (i = 0; i < attr_count; i++)
 		{
+#ifdef	_DROP_COLUMN_HACK__
+			if (COLUMN_IS_DROPPED(attr[i]))
+			{
+				valid[i] = false;
+				continue;
+			}
+			else
+				valid[i] = true;
+#endif /* _DROP_COLUMN_HACK__ */
 			out_func_oid = (Oid) GetOutputFunction(attr[i]->atttypid);
 			fmgr_info(out_func_oid, &out_functions[i]);
 			elements[i] = GetTypeElement(attr[i]->atttypid);
@@ -466,6 +481,14 @@ CopyTo(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null_p
 			value = heap_getattr(tuple, i + 1, tupDesc, &isnull);
 			if (!binary)
 			{
+#ifdef	_DROP_COLUMN_HACK__
+				if (!valid[i])
+				{
+					if (i == attr_count - 1)
+						CopySendChar('\n', fp);
+					continue;
+				}
+#endif /* _DROP_COLUMN_HACK__ */
 				if (!isnull)
 				{
 					string = (char *) (*fmgr_faddr(&out_functions[i]))
@@ -692,6 +715,10 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null
 		typmod = (int32 *) palloc(attr_count * sizeof(int32));
 		for (i = 0; i < attr_count; i++)
 		{
+#ifdef	_DROP_COLUMN_HACK__
+			if (COLUMN_IS_DROPPED(attr[i]))
+				continue;
+#endif /* _DROP_COLUMN_HACK__ */
 			in_func_oid = (Oid) GetInputFunction(attr[i]->atttypid);
 			fmgr_info(in_func_oid, &in_functions[i]);
 			elements[i] = GetTypeElement(attr[i]->atttypid);
@@ -718,6 +745,13 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null
 	{
 		nulls[i] = ' ';
 		index_nulls[i] = ' ';
+#ifdef	_DROP_COLUMN_HACK__
+		if (COLUMN_IS_DROPPED(attr[i]))
+		{
+			byval[i] = 'n';
+			continue;
+		}
+#endif /* _DROP_COLUMN_HACK__ */
 		byval[i] = (bool) IsTypeByVal(attr[i]->atttypid);
 	}
 
@@ -750,6 +784,14 @@ CopyFrom(Relation rel, bool binary, bool oids, FILE *fp, char *delim, char *null
 			}
 			for (i = 0; i < attr_count && !done; i++)
 			{
+#ifdef	_DROP_COLUMN_HACK__
+				if (COLUMN_IS_DROPPED(attr[i]))
+				{
+					values[i] = PointerGetDatum(NULL);
+					nulls[i] = 'n';
+					continue;
+				}
+#endif /* _DROP_COLUMN_HACK__ */
 				string = CopyReadAttribute(fp, &isnull, delim, &newline, null_print);
 				if (isnull)
 				{

src/backend/commands/vacuum.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.142 2000/03/08 23:41:00 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.143 2000/03/09 05:00:23 inoue Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2240,6 +2240,10 @@ vc_attrstats(Relation onerel, VRelStats *vacrelstats, HeapTuple tuple)
 		VacAttrStats *stats = &vacattrstats[i];
 		bool		value_hit = true;
 
+#ifdef	_DROP_COLUMN_HACK__
+		if (COLUMN_IS_DROPPED(stats->attr))
+			continue;
+#endif	/* _DROP_COLUMN_HACK__ */
 		value = heap_getattr(tuple,
 							 stats->attr->attnum, tupDesc, &isnull);
 

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 1.34 2000/01/26 05:56:39 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/prep/preptlist.c,v 1.35 2000/03/09 05:00:24 inoue Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -189,10 +189,20 @@ expand_targetlist(List *tlist, int command_type,
 			{
 				case CMD_INSERT:
 				{
+#ifdef	_DROP_COLUMN_HACK__
+					Datum		typedefault;
+#else
 					Datum		typedefault = get_typdefault(atttype);
+#endif /* _DROP_COLUMN_HACK__ */
 					int			typlen;
 					Const	   *temp_const;
 
+#ifdef	_DROP_COLUMN_HACK__
+					if (COLUMN_IS_DROPPED(att_tup))
+						typedefault = PointerGetDatum(NULL);
+					else
+						typedefault = get_typdefault(atttype);
+#endif /* _DROP_COLUMN_HACK__ */
 					if (typedefault == PointerGetDatum(NULL))
 						typlen = 0;
 					else
@@ -230,8 +240,25 @@ expand_targetlist(List *tlist, int command_type,
 				{
 					Var		   *temp_var;
 
+#ifdef	_DROP_COLUMN_HACK__
+					Node	*temp_node = (Node *) NULL;
+					if (COLUMN_IS_DROPPED(att_tup))
+					{
+						temp_node = (Node *)makeConst(atttype, 								0, 
+							PointerGetDatum(NULL),
+								true,
+								false,
+								false, /* not a set */
+								false);
+					}
+					else
+#endif /* _DROP_COLUMN_HACK__ */
 					temp_var = makeVar(result_relation, attrno, atttype,
 									   atttypmod, 0);
+#ifdef	_DROP_COLUMN_HACK__
+					if (!temp_node)
+						temp_node = (Node *) temp_var;
+#endif /* _DROP_COLUMN_HACK__ */
 
 					new_tle = makeTargetEntry(makeResdom(attrno,
 														 atttype,
@@ -240,7 +267,11 @@ expand_targetlist(List *tlist, int command_type,
 														 0,
 														 (Oid) 0,
 														 false),										
+#ifdef	_DROP_COLUMN_HACK__
+				temp_node);
+#else
 	(Node *) temp_var);
+#endif /* _DROP_COLUMN_HACK__ */
 					break;
 				}
 				default:

src/backend/parser/parse_relation.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.35 2000/02/15 03:37:47 thomas Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_relation.c,v 1.36 2000/03/09 05:00:24 inoue Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -359,6 +359,10 @@ expandTable(ParseState *pstate, char *refname, bool getaliases)
 	{
 		char	   *attrname;
 
+#ifdef	_DROP_COLUMN_HACK__
+		if (COLUMN_IS_DROPPED(rel->rd_att->attrs[varattno]))
+			continue;
+#endif	/* _DROP_COLUMN_HACK__ */
 		attrname = pstrdup(NameStr(rel->rd_att->attrs[varattno]->attname));
 		attr->attrs = lappend(attr->attrs, makeString(attrname));
 	}
@@ -404,6 +408,10 @@ expandAll(ParseState *pstate, char *relname, Attr *ref, int *this_resno)
 		Var			   *varnode;
 		TargetEntry	   *te = makeNode(TargetEntry);
 
+#ifdef	_DROP_COLUMN_HACK__
+		if (COLUMN_IS_DROPPED(rel->rd_att->attrs[varattno]))
+			continue;
+#endif	/* _DROP_COLUMN_HACK__ */
 		attrname = pstrdup(NameStr(rel->rd_att->attrs[varattno]->attname));
 
 		/* varattno is zero-based, so check that length() is always greater */

src/backend/parser/parse_target.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.55 2000/02/15 03:37:47 thomas Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/parse_target.c,v 1.56 2000/03/09 05:00:24 inoue Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -355,6 +355,12 @@ checkInsertTargets(ParseState *pstate, List *cols, List **attrnos)
 		{
 			Ident	   *id = makeNode(Ident);
 
+#ifdef	_DROP_COLUMN_HACK__
+			if (COLUMN_IS_DROPPED(attr[i]))
+			{
+				continue;
+			}
+#endif	/* _DROP_COLUMN_HACK__ */
 			id->name = palloc(NAMEDATALEN);
 			StrNCpy(id->name, NameStr(attr[i]->attname), NAMEDATALEN);
 			id->indirection = NIL;

src/backend/utils/cache/relcache.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.91 2000/02/27 12:02:32 wieck Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.92 2000/03/09 05:00:25 inoue Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -568,6 +568,9 @@ build_tupdesc_ind(RelationBuildDescInfo buildinfo,
 	AttrDefault *attrdef = NULL;
 	int			ndef = 0;
 	int			i;
+#ifdef	_DROP_COLUMN_HACK__
+	bool			columnDropped;
+#endif	/* _DROP_COLUMN_HACK__ */
 
 	constr->has_not_null = false;
 
@@ -575,12 +578,25 @@ build_tupdesc_ind(RelationBuildDescInfo buildinfo,
 
 	for (i = 1; i <= relation->rd_rel->relnatts; i++)
 	{
+#ifdef	_DROP_COLUMN_HACK__
+		columnDropped = false;
+#endif	/* _DROP_COLUMN_HACK__ */
 		atttup = (HeapTuple) AttributeRelidNumIndexScan(attrel,
 										  RelationGetRelid(relation), i);
 
 		if (!HeapTupleIsValid(atttup))
+#ifdef	_DROP_COLUMN_HACK__
+		{
+			atttup = (HeapTuple) AttributeRelidNumIndexScan(attrel,
+										  			RelationGetRelid(relation), DROPPED_COLUMN_INDEX(i));
+			if (!HeapTupleIsValid(atttup))
+#endif	/* _DROP_COLUMN_HACK__ */
 			elog(ERROR, "cannot find attribute %d of relation %s", i,
 				 RelationGetRelationName(relation));
+#ifdef	_DROP_COLUMN_HACK__
+			columnDropped = true;
+		}
+#endif	/* _DROP_COLUMN_HACK__ */
 		attp = (Form_pg_attribute) GETSTRUCT(atttup);
 
 		relation->rd_att->attrs[i - 1] =
@@ -590,6 +606,10 @@ build_tupdesc_ind(RelationBuildDescInfo buildinfo,
 				(char *) attp,
 				ATTRIBUTE_TUPLE_SIZE);
 
+#ifdef	_DROP_COLUMN_HACK__
+		if (columnDropped)
+			continue;
+#endif	/* _DROP_COLUMN_HACK__ */
 		/* Update if this attribute have a constraint */
 		if (attp->attnotnull)
 			constr->has_not_null = true;

src/include/catalog/pg_attribute.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: pg_attribute.h,v 1.53 2000/01/26 05:57:57 momjian Exp $
+ * $Id: pg_attribute.h,v 1.54 2000/03/09 05:00:26 inoue Exp $
  *
  * NOTES
  *	  the genbki.sh script reads this file and generates .bki
@@ -178,6 +178,20 @@ typedef FormData_pg_attribute *Form_pg_attribute;
 #define Anum_pg_attribute_atthasdef		15
 
 
+#ifdef	_DROP_COLUMN_HACK__
+/*
+ *	CONSTANT and MACROS for DROP COLUMN implementation
+ */
+#define	DROP_COLUMN_OFFSET	-20
+#define	COLUMN_IS_DROPPED(attribute)	((attribute)->attnum <= DROP_COLUMN_OFFSET)
+#define	DROPPED_COLUMN_INDEX(attidx)	(DROP_COLUMN_OFFSET - attidx)
+#define	ATTRIBUTE_DROP_COLUMN(attribute) \
+	Assert((attribute)->attnum > 0); \
+	(attribute)->attnum = DROPPED_COLUMN_INDEX((attribute)->attnum); \
+	(attribute)->atttypid = (Oid) -1; \
+	(attribute)->attnotnull = false; \
+	(attribute)->atthasdef = false; 
+#endif	/* _DROP_COLUMN_HACK__ */
 /* ----------------
  *		SCHEMA_ macros for declaring hardcoded tuple descriptors.
  *		these are used in utils/cache/relcache.c