I took my first stab at hacking the sources to fix the bug reported here:
http://archives.postgresql.org/pgsql-bugs/2012-01/msg00152.php
It's such a simple patch but it took me several hours with Google and IRC
and I'm sure I did many things wrong. It seems to work as advertised,
though, so I'm submitting it.
I suppose since I have now submitted a patch, it is my moral obligation to
review at least one. I'm not sure how helpful I'll be, but I'll go bite
the bullet and sign myself up anyway.
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
new file mode 100644
index cb8ac67..7555d19
*** a/src/backend/commands/tablecmds.c
--- b/src/backend/commands/tablecmds.c
*************** ATExecAddColumn(List **wqueue, AlteredTa
*** 4235,4240 ****
--- 4235,4241 ----
List *children;
ListCell *child;
AclResult aclresult;
+ HeapTuple attTuple;
/* At top level, permission check was done in ATPrepCmd, else do it */
if (recursing)
*************** ATExecAddColumn(List **wqueue, AlteredTa
*** 4314,4326 ****
* this test is deliberately not attisdropped-aware, since if one tries to
* add a column matching a dropped column name, it's gonna fail anyway.
*/
! if (SearchSysCacheExists2(ATTNAME,
! ObjectIdGetDatum(myrelid),
! PointerGetDatum(colDef->colname)))
! ereport(ERROR,
! (errcode(ERRCODE_DUPLICATE_COLUMN),
! errmsg("column \"%s\" of relation \"%s\" already exists",
! colDef->colname, RelationGetRelationName(rel))));
/* Determine the new attribute's number */
if (isOid)
--- 4315,4341 ----
* this test is deliberately not attisdropped-aware, since if one tries to
* add a column matching a dropped column name, it's gonna fail anyway.
*/
! attTuple = SearchSysCache2(ATTNAME,
! ObjectIdGetDatum(myrelid),
! PointerGetDatum(colDef->colname));
!
! if (HeapTupleIsValid(attTuple))
! {
! int attnum;
! attnum = ((Form_pg_attribute) GETSTRUCT(attTuple))->attnum;
! if (attnum <= 0)
! ereport(ERROR,
! (errcode(ERRCODE_DUPLICATE_COLUMN),
! errmsg("column \"%s\" conflicts with a system column name",
! colDef->colname)));
! else
! ereport(ERROR,
! (errcode(ERRCODE_DUPLICATE_COLUMN),
! errmsg("column \"%s\" of relation \"%s\" already exists",
! colDef->colname, RelationGetRelationName(rel))));
!
! ReleaseSysCache(attTuple);
! }
/* Determine the new attribute's number */
if (isOid)
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
new file mode 100644
index e992549..8385afb
*** a/src/test/regress/expected/alter_table.out
--- b/src/test/regress/expected/alter_table.out
*************** COMMENT ON TABLE tmp_wrong IS 'table com
*** 7,12 ****
--- 7,14 ----
ERROR: relation "tmp_wrong" does not exist
COMMENT ON TABLE tmp IS 'table comment';
COMMENT ON TABLE tmp IS NULL;
+ ALTER TABLE tmp ADD COLUMN xmin integer; -- fails
+ ERROR: column "xmin" conflicts with a system column name
ALTER TABLE tmp ADD COLUMN a int4 default 3;
ALTER TABLE tmp ADD COLUMN b name;
ALTER TABLE tmp ADD COLUMN c text;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
new file mode 100644
index d9bf08d..d4e4c49
*** a/src/test/regress/sql/alter_table.sql
--- b/src/test/regress/sql/alter_table.sql
*************** COMMENT ON TABLE tmp_wrong IS 'table com
*** 9,14 ****
--- 9,16 ----
COMMENT ON TABLE tmp IS 'table comment';
COMMENT ON TABLE tmp IS NULL;
+ ALTER TABLE tmp ADD COLUMN xmin integer; -- fails
+
ALTER TABLE tmp ADD COLUMN a int4 default 3;
ALTER TABLE tmp ADD COLUMN b name;
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