MDEV-29092 FOREIGN_KEY_CHECKS does not prevent non-copy alter from creating invalid FK structure

Problem:
========
- InnoDB should have two keys on the same column for the self
referencing foreign key relation.

Solution:
=========
- Allow self referential foreign key relation to work with one
key.

mysql-test/suite/innodb/r/innodb-index-online-fk.result

@@ -654,3 +654,34 @@ t2	CREATE TABLE `t2` (
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 drop table t2;
 drop table t1;
+#
+#  MDEV-29092  FOREIGN_KEY_CHECKS does not prevent non-copy
+#               alter from creating invalid FK structures
+#
+CREATE TABLE t1(f1 INT, KEY(f1),
+FOREIGN KEY(f1) references t1(f1))ENGINE=InnoDB;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) DEFAULT NULL,
+  KEY `f1` (`f1`),
+  CONSTRAINT `t1_ibfk_1` FOREIGN KEY (`f1`) REFERENCES `t1` (`f1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+DROP TABLE t1;
+CREATE TABLE t1(f1 INT, KEY(f1),
+FOREIGN KEY(f1) REFERENCES t1(f1))ENGINE=InnoDB;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) DEFAULT NULL,
+  KEY `f1` (`f1`),
+  CONSTRAINT `t1_ibfk_1` FOREIGN KEY (`f1`) REFERENCES `t1` (`f1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+ALTER TABLE t1 DROP KEY f1;
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `f1` int(11) DEFAULT NULL,
+  CONSTRAINT `t1_ibfk_1` FOREIGN KEY (`f1`) REFERENCES `t1` (`f1`)
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+DROP TABLE t1;

mysql-test/suite/innodb/r/innodb-truncate.result

@@ -86,8 +86,7 @@ CREATE TABLE t2 (f2 INT, FOREIGN KEY(f2) REFERENCES t1 (f2)) ENGINE=InnoDB;
 CREATE TABLE t3 (a INT) ENGINE=InnoDB;
 ERROR HY000: Can't create table `test`.`t3` (errno: 150 "Foreign key constraint is incorrectly formed")
 ALTER TABLE t1 RENAME TO t3;
-ERROR HY000: Error on rename of './test/t1' to './test/t3' (errno: 150 "Foreign key constraint is incorrectly formed")
+ALTER TABLE t3 FORCE;
-ALTER TABLE t1 FORCE;
+TRUNCATE TABLE t3;
-TRUNCATE TABLE t1;
 ERROR 42000: Cannot truncate a table referenced in a foreign key constraint (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`f2`) REFERENCES `test`.`t3` (`f2`))
-DROP TABLE t2, t1;
+DROP TABLE t2, t3;

mysql-test/suite/innodb/r/innodb_bug12902967.result

@@ -1,6 +0,0 @@
-call mtr.add_suppression("In ALTER TABLE .* has or is referenced in foreign key constraints which are not compatible with the new table definition.");
-# restart
-create table t1 (f1 integer primary key) engine innodb;
-alter table t1 add constraint c1 foreign key (f1) references t1(f1);
-ERROR HY000: Error on rename of '#sql-temporary' to './test/t1' (errno: 150 "Foreign key constraint is incorrectly formed")
-drop table t1;

mysql-test/suite/innodb/t/innodb-index-online-fk.test

@@ -511,3 +511,19 @@ alter table t2 drop key t,algorithm=inplace;
 show create table t2;
 drop table t2;
 drop table t1;
+
+--echo #
+--echo #  MDEV-29092  FOREIGN_KEY_CHECKS does not prevent non-copy
+--echo #               alter from creating invalid FK structures
+--echo #
+CREATE TABLE t1(f1 INT, KEY(f1),
+                FOREIGN KEY(f1) references t1(f1))ENGINE=InnoDB;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+CREATE TABLE t1(f1 INT, KEY(f1),
+                FOREIGN KEY(f1) REFERENCES t1(f1))ENGINE=InnoDB;
+SHOW CREATE TABLE t1;
+ALTER TABLE t1 DROP KEY f1;
+SHOW CREATE TABLE t1;
+DROP TABLE t1;

mysql-test/suite/innodb/t/innodb-truncate.test

@@ -85,10 +85,8 @@ SET FOREIGN_KEY_CHECKS= ON;
 CREATE TABLE t2 (f2 INT, FOREIGN KEY(f2) REFERENCES t1 (f2)) ENGINE=InnoDB;
 --error ER_CANT_CREATE_TABLE
 CREATE TABLE t3 (a INT) ENGINE=InnoDB;
---replace_result $datadir ./
---error ER_ERROR_ON_RENAME
 ALTER TABLE t1 RENAME TO t3;
-ALTER TABLE t1 FORCE;
+ALTER TABLE t3 FORCE;
 --error ER_TRUNCATE_ILLEGAL_FK
-TRUNCATE TABLE t1;
+TRUNCATE TABLE t3;
-DROP TABLE t2, t1;
+DROP TABLE t2, t3;

mysql-test/suite/innodb/t/innodb_bug12902967.test

@@ -1,25 +0,0 @@
-# Bug 12902967: Creating self referencing fk on same index unhandled,
-# confusing error
-#
-# Creating a self referencing foreign key on the same
-# column/index is an unhandled exception, it should throw a sensible
-# error but instead implies that your data dictionary may now be out
-# of sync:
-
---source include/have_innodb.inc
---source include/not_embedded.inc
-
-call mtr.add_suppression("In ALTER TABLE .* has or is referenced in foreign key constraints which are not compatible with the new table definition.");
-
-let error_log= $MYSQLTEST_VARDIR/log/mysqld.1.err;
---source include/restart_mysqld.inc
-
-create table t1 (f1 integer primary key) engine innodb;
-
-# The below statement should produce error message in error log.
-# This error message should mention problem with foreign keys
-# rather than with data dictionary.
---replace_regex /'\.\/test\/#sql-[0-9a-f_]*'/'#sql-temporary'/
---error ER_ERROR_ON_RENAME
-alter table t1 add constraint c1 foreign key (f1) references t1(f1);
-drop table t1;

storage/innobase/dict/dict0dict.cc

@@ -2697,8 +2697,7 @@ dict_foreign_find_index(
 	for (dict_index_t* index = dict_table_get_first_index(table);
 	     index;
 	     index = dict_table_get_next_index(index)) {
-		if (types_idx != index
+		if (!index->to_be_dropped
-		    && !index->to_be_dropped
 		    && !dict_index_is_online_ddl(index)
 		    && dict_foreign_qualify_index(
 			    table, col_names, columns, n_cols,