Assertion `err != DB_DUPLICATE_KEY' failed in row_rename_table_for_mysql & ERROR 1050 (42S01): Table './test/t1' already exists for simple ALTER TABLE on optimized builds (Related to MDEV-25509)

SET old_alter_table=1;

CREATE TABLE t1 (a VARCHAR(10) NOT NULL PRIMARY KEY) ENGINE=InnoDB;

CREATE TABLE t1_fk (a VARCHAR(40), KEY a (a), FULLTEXT KEY(a), CONSTRAINT fk FOREIGN KEY(a) REFERENCES t1 (a) ON UPDATE CASCADE) ENGINE=InnoDB;

ALTER TABLE t1 RENAME TO tm1;

CREATE TABLE t1 (c1 BIGINT NOT NULL, c2 BIGINT NOT NULL, PRIMARY KEY(c1), UNIQUE KEY(c2)) ENGINE=MEMORY;

ALTER TABLE t1 ENGINE=InnoDB;

10.6.1-opt>SET old_alter_table=1;

Query OK, 0 rows affected, 1 warning (0.000 sec)

10.6.1-opt>CREATE TABLE t1 (a VARCHAR(10) NOT NULL PRIMARY KEY) ENGINE=InnoDB;

Query OK, 0 rows affected (0.015 sec)

10.6.1-opt>CREATE TABLE t1_fk (a VARCHAR(40), KEY a (a), FULLTEXT KEY(a), CONSTRAINT fk FOREIGN KEY(a) REFERENCES t1 (a) ON UPDATE CASCADE) ENGINE=InnoDB;

Query OK, 0 rows affected (0.091 sec)

10.6.1-opt>ALTER TABLE t1 RENAME TO tm1;

ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails

10.6.1-opt>CREATE TABLE t1 (c1 BIGINT NOT NULL, c2 BIGINT NOT NULL, PRIMARY KEY(c1), UNIQUE KEY(c2)) ENGINE=MEMORY;

Query OK, 0 rows affected (0.008 sec)

10.6.1-opt>ALTER TABLE t1 ENGINE=InnoDB;

ERROR 1050 (42S01): Table './test/t1' already exists

10.6.1-opt>