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Make the world at least somewhat safe for zero-column tables, and

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remove the special case in ALTER DROP COLUMN to prohibit dropping a
table's last column.
This commit is contained in:
Tom Lane
2002-09-28 20:00:19 +00:00
parent 23616b47d5
commit 6d0d15c451
6 changed files with 64 additions and 81 deletions
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29
src/backend/commands/tablecmds.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.44 2002/09/23 20:43:40 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.45 2002/09/28 20:00:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -2331,9 +2331,7 @@ AlterTableDropColumn(Oid myrelid, bool recurse, bool recursing,
{
Relation rel;
AttrNumber attnum;
AttrNumber n;
TupleDesc tupleDesc;
bool success;
ObjectAddress object;
rel = heap_open(myrelid, AccessExclusiveLock);
@ -2359,34 +2357,13 @@ AlterTableDropColumn(Oid myrelid, bool recurse, bool recursing,
RelationGetRelationName(rel), colName);
/* Can't drop a system attribute */
/* XXX perhaps someday allow dropping OID? */
if (attnum < 0)
elog(ERROR, "ALTER TABLE: Cannot drop system attribute \"%s\"",
colName);
/*
* Make sure there will be at least one user column left in the
* relation after we drop this one. Zero-length tuples tend to
* confuse us.
*/
tupleDesc = RelationGetDescr(rel);
success = false;
for (n = 1; n <= tupleDesc->natts; n++)
{
Form_pg_attribute attribute = tupleDesc->attrs[n - 1];
if (!attribute->attisdropped && n != attnum)
{
success = true;
break;
}
}
if (!success)
elog(ERROR, "ALTER TABLE: Cannot drop last column from table \"%s\"",
RelationGetRelationName(rel));
/* Don't drop inherited columns */
tupleDesc = RelationGetDescr(rel);
if (tupleDesc->attrs[attnum - 1]->attinhcount > 0 && !recursing)
elog(ERROR, "ALTER TABLE: Cannot drop inherited column \"%s\"",
colName);