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Re: MariaDB 10.4: subtle change of result ordering


‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Friday, August 21, 2020 12:18 PM, Reindl Harald <h.reindl@xxxxxxxxxxxxx> wrote:

> in all previous versions this test was stable, so as the timestamps are
> identical and ordering is 'desc' the result was ordered by the creation
> time of the the records
> now it's reverse which can break all sort of expectations in subtle ways
> while we could discuss what is the expected output when order by
> 'ktimestamp' and all are identical it still worries me that something
> which didn't change over years and major versions now comes with the
> reverse ordering
> unless someone tells me that's the result of some real peformance
> optimization i would perfer the known result given that it's hard to
> know how much other code depends implicit on the previous behavior

I would say that the actual ordering of the records below obtained by the select command shown is undefined. I can very well change for whatever subtle change in code.

AFAIU, if you need repeatable results, you need to write a select command with a deterministic result.

If this test has been presenting repeatable results for a long time, that's just chance.

But that's just the opinion of a MariaDB user. I'm no developer. I would like to know the opinion of the developers.


Rodrigo Severo

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