During heap rebuild, lock any TOAST index until end of transaction.

nmisch · nmisch · commit 78a34c68920a · 2020-03-21T09:38:34.000-07:00
swap_relation_files() calls toast_get_valid_index() to find and lock this index, just before swapping with the rebuilt TOAST index. The latter function releases the lock before returning. Potential for mischief is low; a concurrent session can issue ALTER INDEX ... SET (fillfactor = ...), which is not alarming. Nonetheless, changing pg_class.relfilenode without a lock is unconventional. Back-patch to 9.5 (all supported versions), because another fix needs this. Discussion: https://postgr.es/m/20191226001521.GA1772687@rfd.leadboat.com
diff --git a/src/backend/access/heap/tuptoaster.c b/src/backend/access/heap/tuptoaster.c
@@ -1447,8 +1447,8 @@ toast_get_valid_index(Oid toastoid, LOCKMODE lock)
 	validIndexOid = RelationGetRelid(toastidxs[validIndex]);
 
 	/* Close the toast relation and all its indexes */
-	toast_close_indexes(toastidxs, num_indexes, lock);
-	heap_close(toastrel, lock);
+	toast_close_indexes(toastidxs, num_indexes, NoLock);
+	heap_close(toastrel, NoLock);
 
 	return validIndexOid;
 }
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
@@ -1636,7 +1636,7 @@ finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
 
 			/* Get the associated valid index to be renamed */
 			toastidx = toast_get_valid_index(newrel->rd_rel->reltoastrelid,
-											 AccessShareLock);
+											 NoLock);
 
 			/* rename the toast table ... */
 			snprintf(NewToastName, NAMEDATALEN, "pg_toast_%u",

Original file line number	Diff line number	Diff line change
`@@ -1447,8 +1447,8 @@ toast_get_valid_index(Oid toastoid, LOCKMODE lock)`
`1447`	`1447`	`validIndexOid = RelationGetRelid(toastidxs[validIndex]);`
`1448`	`1448`
`1449`	`1449`	`/* Close the toast relation and all its indexes */`
`1450`		`- toast_close_indexes(toastidxs, num_indexes, lock);`
`1451`		`- heap_close(toastrel, lock);`
	`1450`	`+ toast_close_indexes(toastidxs, num_indexes, NoLock);`
	`1451`	`+ heap_close(toastrel, NoLock);`
`1452`	`1452`
`1453`	`1453`	`return validIndexOid;`
`1454`	`1454`	`}`