Instead of using slightly-too-clever heuristics to decide when we must
create a TOAST table, just check whether one is needed every time the
table is altered. Checking whether a toast table is needed is cheap
enough that we needn't worry about doing it on every ALTER TABLE command,
and the previous coding is apparently prone to accidental breakage:
commit
04e17bae50a73af524731fa11210d5c3f7d8e1f9 broken ALTER TABLE ..
SET STORAGE, which moved some actions from AT_PASS_COL_ATTRS to
AT_PASS_MISC, and commit
6c5723998594dffa5d47c3cf8c96ccf89c033aae broke
ALTER TABLE .. ADD COLUMN by changing the way that adding columns
recurses into child tables.
Noah Misch, with one comment change by me
Relation rel;
/*
- * Grab an exclusive lock on the target table, which we will NOT release
- * until end of transaction. (This is probably redundant in all present
- * uses...)
+ * Grab a DDL-exclusive lock on the target table, since we'll update the
+ * pg_class tuple. This is redundant for all present users. Tuple toasting
+ * behaves safely in the face of a concurrent TOAST table add.
*/
- rel = heap_open(relOid, AccessExclusiveLock);
+ rel = heap_open(relOid, ShareUpdateExclusiveLock);
/* create_toast_table does all the work */
(void) create_toast_table(rel, InvalidOid, InvalidOid, reloptions);
/*
* create_toast_table --- internal workhorse
*
- * rel is already opened and exclusive-locked
+ * rel is already opened and locked
* toastOid and toastIndexOid are normally InvalidOid, but during
* bootstrap they can be nonzero to specify hand-assigned OIDs
*/
}
}
- /*
- * Check to see if a toast table must be added, if we executed any
- * subcommands that might have added a column or changed column storage.
- */
+ /* Check to see if a toast table must be added. */
foreach(ltab, *wqueue)
{
AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
- if (tab->relkind == RELKIND_RELATION &&
- (tab->subcmds[AT_PASS_ADD_COL] ||
- tab->subcmds[AT_PASS_ALTER_TYPE] ||
- tab->subcmds[AT_PASS_COL_ATTRS]))
+ if (tab->relkind == RELKIND_RELATION)
AlterTableCreateToastTable(tab->relid, (Datum) 0);
}
}
alter table recur1 add column f2 int;
alter table recur1 alter column f2 type recur2; -- fails
ERROR: composite type recur1 cannot be made a member of itself
+-- SET STORAGE may need to add a TOAST table
+create table test_storage (a text);
+alter table test_storage alter a set storage plain;
+alter table test_storage add b int default 0; -- rewrite table to remove its TOAST table
+alter table test_storage alter a set storage extended; -- re-add TOAST table
+select reltoastrelid <> 0 as has_toast_table
+from pg_class
+where oid = 'test_storage'::regclass;
+ has_toast_table
+-----------------
+ t
+(1 row)
+
--
-- lock levels
--
ALTER TABLE a_star* ADD COLUMN a text;
+-- That ALTER TABLE should have added TOAST tables.
+SELECT relname, reltoastrelid <> 0 AS has_toast_table
+ FROM pg_class
+ WHERE oid::regclass IN ('a_star', 'c_star')
+ ORDER BY 1;
+
--UPDATE b_star*
-- SET a = text 'gazpacho'
-- WHERE aa > 4;
ALTER TABLE a_star* ADD COLUMN a text;
NOTICE: merging definition of column "a" for child "d_star"
+-- That ALTER TABLE should have added TOAST tables.
+SELECT relname, reltoastrelid <> 0 AS has_toast_table
+ FROM pg_class
+ WHERE oid::regclass IN ('a_star', 'c_star')
+ ORDER BY 1;
+ relname | has_toast_table
+---------+-----------------
+ a_star | t
+ c_star | t
+(2 rows)
+
--UPDATE b_star*
-- SET a = text 'gazpacho'
-- WHERE aa > 4;
alter table recur1 add column f2 int;
alter table recur1 alter column f2 type recur2; -- fails
+-- SET STORAGE may need to add a TOAST table
+create table test_storage (a text);
+alter table test_storage alter a set storage plain;
+alter table test_storage add b int default 0; -- rewrite table to remove its TOAST table
+alter table test_storage alter a set storage extended; -- re-add TOAST table
+
+select reltoastrelid <> 0 as has_toast_table
+from pg_class
+where oid = 'test_storage'::regclass;
+
--
-- lock levels
--