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Re: Please review a patch for MDEV-19284 and MDEV-19285 (instant ALTER)
Hello, Marko, Alexander.
23.04.2019, 15:37, "Marko Mäkelä" <marko.makela@xxxxxxxxxxx>:
> Bar, thank you for the revision.
> I ran all tests and found a regression for ROW_FORMAT=REDUNDANT, in
> the test innodb.instant_alter_charset,redundant. We should allow any
> extension of VARCHAR maximum length (in bytes) for
> ROW_FORMAT=REDUNDANT. The test attempts to enlarge the column from
> 50*3 to 200*3 bytes. That cannot work for other ROW_FORMAT in InnoDB,
> but it does for ROW_FORMAT=REDUNDANT.
I think it's mostly broken test rather a code regression.
Now there is only one case when field length can be increased due to charset change
and it's utf8mb3 -> utf8mb4.
I think the only test case we need now is CHAR(70) UTF8MB3 -> CHAR(70) UTF8MB4
It should work only fro ROW_FORMAT=REDUNDANT
> Also, please check the spelling once more. I found "Uncode-1.1" in a comment.
> See also the Description of MDEV-18584. I’d want to allow a few more
> instantaneous conversion of CHAR columns in InnoDB.
> I agree that the (table->file->ha_table_flags() &
> HA_EXTENDED_TYPES_CONVERSION) is a bit ugly and could be replaced with
> something more descriptive.
> On Fri, Apr 19, 2019 at 2:24 PM Alexander Barkov <bar@xxxxxxxxxxx> wrote:
>> Hi Marko, Eugene,
>> Thanks for good suggestions. A new version is attached.
>> See details inline:
>> On 4/19/19 2:46 PM, Marko Mäkelä wrote:
>> > Hi Bar,
>> > I see that these bugs were based on wrong assumptions that ASCII or
>> > UCS2 columns would only contain valid ASCII or UTF-16 data. We should
>> > have tested these assumptions during the development of MDEV-15564.
>> > Luckily these were found before the GA release of MariaDB 10.4.
>> That was my fault. When we had discussions on this topic with
>> Eugene, I overlooked these problems. Sorry for this.
>> > Here is just a quick note before I will return to work on Tuesday.
>> > Please remove ,algorithm=copy from tests. Instead, use
>> > --enable_info
>> > alter table ...
>> > --disable_info
>> > and make sure that the table contains at least 1 row when the ALTER
>> > TABLE is executed. In that way, ALGORITHM=COPY will report that a
>> > nonzero amount of rows were affected, while the native ALTER would
>> > report that 0 rows were affected.
>> I added this into the new tests in the end of instant_alter_charset.test
>> Note, I didn't add this into original MDEV-15564 tests,
>> as they mostly use empty tables.
>> > I would also suggest testing with some bad data (non-ASCII chars in
>> > ASCII column, or Unicode surrogate pairs in UCS2) to see what kind of
>> > errors would be triggered (if any), or what the converted data would
>> > look like after ALTER IGNORE TABLE.
>> This is a very good idea. I've just added "ALTER IGNORE"s
>> into the new tests.
>> > Please run the commit comment through a spell-checker. I spotted the
>> > typos "correspoding" and "actuallt".
>> > Also, please mention in the commit comment that these are regressions
>> > caused by MDEV-15564. That should make our lifes easier, should we
>> > ever decide to backport MDEV-15564 to earlier versions.
>> > I will review the code and tests in detail next week. I hope that
>> > Eugene can review it as well.
>> > Best regards,
>> > Marko
> Marko Mäkelä, Lead Developer InnoDB
> MariaDB Corporation