MDEV-29504/MDEV-29849 TRUNCATE breaks FOREIGN KEY lockingbb-10.6-MDEV-29849

ha_innobase::referenced_by_foreign_key(): Protect the check with
dict_sys.freeze(), to prevent races with TRUNCATE TABLE.
The test innodb.instant_alter_crash has been adjusted for this
additional locking.

dict_table_is_referenced_by_foreign_key(): Removed (merged to
the only caller).

create_table_info_t::create_table(): Ignore missing indexes for
FOREIGN KEY constraints if foreign_key_checks=0.

create_table_info_t::create_table_update_dict(): Rewritten as
a static function. Do not return any error.

ha_innobase::create(): When trx!=nullptr and we are operating
on a persistent table, do not rollback, commit, or release the
data dictionary latch.

ha_innobase::truncate(): Protect the entire critical section
with an exclusive dict_sys.latch, so that
ha_innobase::referenced_by_foreign_key() on referenced tables
will return a consistent result. In case of a failure,
invoke dict_load_foreigns() to restore also any FOREIGN KEY
constraints.

ha_innobase::free_foreign_key_create_info(): Define inline.

lock_release(): Disregard innodb_evict_tables_on_commit_debug=ON
when dict_sys.locked() holds. It would hold when fts_load_stopword()
is invoked by create_table_info_t::create_table_update_dict().

dict_sys_t::locked(): Return whether the current thread is holding
the exclusive dict_sys.latch.

dict_sys_t::frozen_not_locked(): Return whether any thread is
holding a shared dict_sys.latch.

1 files changed, 11 insertions, 1 deletions

diff --git a/mysql-test/suite/innodb/t/innodb.test b/mysql-test/suite/innodb/t/innodb.test
index 3a8c12dfbbd..3b3b2770df7 100644
--- a/mysql-test/suite/innodb/t/innodb.test
+++ b/mysql-test/suite/innodb/t/innodb.test
@@ -1598,12 +1598,22 @@ disconnect b;
 
 set foreign_key_checks=0;
 create table t2 (a int primary key, b int, foreign key (b) references t1(a)) engine = innodb;
+create table t1(a char(10) primary key, b varchar(20)) engine = innodb;
+set foreign_key_checks=1;
+--error ER_NO_REFERENCED_ROW_2
+insert into t2 values (1,1);
+set foreign_key_checks=0;
+drop table t1;
+set foreign_key_checks=1;
+--error ER_NO_REFERENCED_ROW_2
+insert into t2 values (1,1);
 # Embedded server doesn't chdir to data directory
 --replace_result $MYSQLTEST_VARDIR . master-data/ ''
 --error ER_CANT_CREATE_TABLE
 create table t1(a char(10) primary key, b varchar(20)) engine = innodb;
-set foreign_key_checks=1;
 drop table t2;
+create table t1(a char(10) primary key, b varchar(20)) engine = innodb;
+drop table t1;
 
 # test that FKs between different charsets are not accepted in CREATE even
 # when f_k_c is 0