[ Avaa Bypassed ]

SET DEBUG_SYNC='RESET';
CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 INT, INDEX(c2)) ENGINE = InnoDB;
CREATE TABLE t2 (
c2 INT PRIMARY KEY,
CONSTRAINT t2c2 FOREIGN KEY (c2) REFERENCES t1 (c2))
ENGINE = InnoDB;
DROP INDEX c2 ON t1;
ERROR HY000: Cannot drop index 'c2': needed in a foreign key constraint
DROP TABLE t2;
SET DEBUG_SYNC = 'innodb_after_inplace_alter_table SIGNAL drop WAIT_FOR fk';
DROP INDEX c2 ON t1;
# Establish session con1 (user=root)
# Session con1
SET DEBUG_SYNC = 'now WAIT_FOR drop';
CREATE TABLE t2 (
c2 INT PRIMARY KEY,
CONSTRAINT t2c2 FOREIGN KEY (c2) REFERENCES t1 (c2))
ENGINE = InnoDB;
ERROR HY000: Cannot add foreign key constraint
SET DEBUG_SYNC = 'now SIGNAL fk';
# Session default
/* reap */ DROP INDEX c2 ON t1;
CREATE TABLE t2 (
c2 INT PRIMARY KEY,
CONSTRAINT t2c2 FOREIGN KEY (c2) REFERENCES t1 (c2))
ENGINE = InnoDB;
ERROR HY000: Cannot add foreign key constraint
SET DEBUG_SYNC='RESET';
DROP TABLE t1;