5b665f0069
MDEV-38716 (fa36b269f1) fixes were incomplete. It still allowed a
table's default_fields to be left un-restored after an ALTER table
finished its copy_data_between_fields().
This patch actually matches the original conception of MDEV-38716. It
was later changed after finding a test failure in maria.alter, where I
thought the patch broke that test. But actually, maria.alter itself
relies on somewhat broken/inconsistent server behavior.
It is the MDEV-19055 extension of the test which broke. To summarize the
broken part of the test, first, it creates a temporary table t2, adds a
new column of type DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP, and adds
a constraint check on that new type:
CREATE TEMPORARY TABLE t2 (a TIME) ENGINE=Aria;
ALTER TABLE t2 ADD b DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP;
ALTER TABLE t2 ADD CHECK (b = 4);
The next part results in inconsistent behavior:
INSERT IGNORE INTO t2 () VALUES (),(),(),();
Prior to this patch, this would create 4 new rows, each with a zeroed
out timestamp for `b`. This is due to a the default_field not resetting
after the ALTER TABLE, thus the DEFAULT CURRENT_TIMESTAMP clause is lost
after the ALTER TABLE ADD CHECK.
With this patch, because the default_field is restored after the ALTER,
there is no affect of the INSERT IGNORE INTO t2. I.e., t2 is empty after
this insert.
This change in results further changes how an ALTER TABLE behaves later
in the test:
SET SQL_MODE= 'STRICT_ALL_TABLES';
SELECT count(a),sum(a) FROM t2;
--error ER_TRUNCATED_WRONG_VALUE
ALTER TABLE t2 CHANGE IF EXISTS d c INT;
Without this patch, there are rows in t2, and so this ALTER TABLE
results in an error. With this patch, t2 is empty, and therefore there
is no data that was truncated to warn about. It is generally bad test
practice to have a table with no rows, as it has historically masked
other bugs. So we add back a couple rows into the table to ensure it
hits additional logic. However, because the bug has been fixed, invalid
rows are not able to be inserted into the table and thereby the
ER_TRUNCATED_WRONG_VALUE error is still not thrown. So that error is
removed.
Reviewed-by: Monty <monty@mariadb.com>
Signed-off-by: Brandon Nesterenko <brandon.nesterenko@mariadb.com>
Code status:
ci.appveyor.com
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