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MDEV-18775 Fix ALTER TABLE error handling for DROP INDEX

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On an error (such as when an index cannot be dropped due to
FOREIGN KEY constraints), the field dict_index_t::to_be_dropped
was only being cleared in debug builds, even though the field
is available and being used also in non-debug builds.

This was a regression that was introduced by myself originally
in MySQL 5.7.6 and later merged to MariaDB 10.2.2, in
d39898de8e

An error manifested itself in the MariaDB Server 10.4 non-debug build,
involving instant ADD or DROP column. Because an earlier failed
ALTER TABLE operation incorrectly left the dict_index_t::to_be_dropped
flag set, the column pointers of the index fields would fail to be
adjusted for instant ADD or DROP column (MDEV-15562). The instant
ADD COLUMN in MariaDB Server 10.3 is unlikely to be affected by a
similar scenario, because dict_table_t::instant_add_column() in 10.3
is applying the transformations to all indexes, not skipping
to-be-dropped ones.
This commit is contained in:
Marko Mäkelä
2019-03-01 10:16:56 +02:00
parent 003b507416
commit 4a1c66290d
3 changed files with 36 additions and 2 deletions
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15
mysql-test/suite/innodb/r/alter_table.result
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@ -38,3 +38,18 @@ Warnings:
Warning 1105 ORDER BY ignored as there is a user-defined clustered index in the table 't1'
DROP TABLE t1;
SET sql_mode=DEFAULT;
#
# MDEV-18775 Server crashes in dict_table_t::instant_column
# upon ADD COLUMN
#
CREATE TABLE tx (pk INT PRIMARY KEY) ENGINE=InnoDB;
CREATE TABLE t1 (pk INT, a INT, PRIMARY KEY (pk), KEY (a), FOREIGN KEY (a) REFERENCES tx (pk)) ENGINE=InnoDB;
SET FOREIGN_KEY_CHECKS=OFF;
ALTER TABLE t1 DROP a;
ERROR HY000: Cannot drop column 'a': needed in a foreign key constraint 'test/t1_ibfk_1'
SET FOREIGN_KEY_CHECKS=ON;
ALTER TABLE t1 ADD b INT;
ALTER TABLE t1 DROP a;
ERROR HY000: Cannot drop index 'a': needed in a foreign key constraint
ALTER TABLE t1 ADD c INT;
DROP TABLE t1, tx;