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Re: Please review a patch for MDEV-19284 and MDEV-19285 (instant ALTER)
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.
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