Fix toast table creation.

robertmhaas · robertmhaas · commit 39a68e5c6ca7 · 2011-04-13T18:17:52.000-07:00
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 04e17ba broken ALTER TABLE .. SET STORAGE, which moved some actions from AT_PASS_COL_ATTRS to AT_PASS_MISC, and commit 6c57239 broke ALTER TABLE .. ADD COLUMN by changing the way that adding columns recurses into child tables. Noah Misch, with one comment change by me
diff --git a/src/backend/catalog/toasting.c b/src/backend/catalog/toasting.c
@@ -59,11 +59,11 @@ AlterTableCreateToastTable(Oid relOid, Datum reloptions)
 	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);
@@ -103,7 +103,7 @@ BootstrapToastTable(char *relName, Oid toastOid, Oid toastIndexOid)
 /*
  * 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
  */
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
@@ -3022,18 +3022,12 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode)
 		}
 	}
 
-	/*
-	 * 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);
 	}
 }
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
@@ -1522,6 +1522,19 @@ ERROR:  composite type recur1 cannot be made a member of itself
 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
 --
diff --git a/src/test/regress/input/misc.source b/src/test/regress/input/misc.source
@@ -153,6 +153,12 @@ SELECT * FROM e_star*;
 
 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;
diff --git a/src/test/regress/output/misc.source b/src/test/regress/output/misc.source
@@ -376,6 +376,17 @@ SELECT * FROM e_star*;
 
 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;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
@@ -1133,6 +1133,16 @@ alter table recur1 add column f2 recur2; -- fails
 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
 --

Original file line number	Diff line number	Diff line change
`@@ -3022,18 +3022,12 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode)`
`3022`	`3022`	`}`
`3023`	`3023`	`}`
`3024`	`3024`
`3025`		`- /*`
`3026`		`- * Check to see if a toast table must be added, if we executed any`
`3027`		`- * subcommands that might have added a column or changed column storage.`
`3028`		`- */`
	`3025`	`+ /* Check to see if a toast table must be added. */`
`3029`	`3026`	`foreach(ltab, *wqueue)`
`3030`	`3027`	`{`
`3031`	`3028`	`AlteredTableInfo tab = (AlteredTableInfo ) lfirst(ltab);`
`3032`	`3029`
`3033`		`- if (tab->relkind == RELKIND_RELATION &&`
`3034`		`- (tab->subcmds[AT_PASS_ADD_COL] \|\|`
`3035`		`- tab->subcmds[AT_PASS_ALTER_TYPE] \|\|`
`3036`		`- tab->subcmds[AT_PASS_COL_ATTRS]))`
	`3030`	`+ if (tab->relkind == RELKIND_RELATION)`
`3037`	`3031`	`AlterTableCreateToastTable(tab->relid, (Datum) 0);`
`3038`	`3032`	`}`
`3039`	`3033`	`}`