MDEV-12669 Circular foreign keys cause a loop and OOM upon LOCK TABLE

table_already_fk_prelocked() was looking for a table in the wrong
list (not the complete list of prelocked tables, but only in its tail,
starting from the current table - which is always empty for the last
added table), so for circular FKs it kept adding same tables to the list
indefinitely.

Backport of d6d7e169fbf

1 files changed, 19 insertions, 0 deletions

diff --git a/mysql-test/suite/innodb/r/foreign_key.result b/mysql-test/suite/innodb/r/foreign_key.result
new file mode 100644
index 00000000000..0d04f27f51f
--- /dev/null
+++ b/mysql-test/suite/innodb/r/foreign_key.result
@@ -0,0 +1,19 @@
+SET FOREIGN_KEY_CHECKS=0;
+CREATE TABLE staff (
+staff_id TINYINT UNSIGNED NOT NULL AUTO_INCREMENT,
+store_id TINYINT UNSIGNED NOT NULL,
+PRIMARY KEY  (staff_id),
+KEY idx_fk_store_id (store_id),
+CONSTRAINT fk_staff_store FOREIGN KEY (store_id) REFERENCES store (store_id) ON DELETE RESTRICT ON UPDATE CASCADE
+) ENGINE=InnoDB;
+CREATE TABLE store (
+store_id TINYINT UNSIGNED NOT NULL AUTO_INCREMENT,
+manager_staff_id TINYINT UNSIGNED NOT NULL,
+PRIMARY KEY  (store_id),
+UNIQUE KEY idx_unique_manager (manager_staff_id),
+CONSTRAINT fk_store_staff FOREIGN KEY (manager_staff_id) REFERENCES staff (staff_id) ON DELETE RESTRICT ON UPDATE CASCADE
+) ENGINE=InnoDB;
+SET FOREIGN_KEY_CHECKS=DEFAULT;
+LOCK TABLE staff WRITE;
+UNLOCK TABLES;
+DROP TABLES staff, store;