Hi, Reindl! On Aug 24, Reindl Harald wrote:
Am 24.08.20 um 14:23 schrieb Sergei Golubchik:
Sorry, I couldn't understand, was 10.3 returning 3..2..1 and 10.4 started to return 1..2..3? Or was it the other way around?
that at a bottom is a unified iff between expected output and what happens when trying 10.4.14
10.2 and 10.3 returning 1-2-3 for years 10.4.14 in the identical environemnt returns 3-2-1
* they are created 1-2-3 * timestamps identical because created in same second * 'desc' ordering by timestamp gave 1-2-3
my issue is not that the result as such could be called wrong but that it changes after years, the autotests which is part of a bug testsuite has the expected HTML output base64 decoded, fires a diff against the now created html-output and alerts if there is a byte changed
Yes, I understand that. But, as I just wrote:
I tried your table structure and your test data on both 10.3 and 10.5 and in both cases I've got 3..2..1
What happens in my tests - decides to use the comment_key_1 index. It reads the index backwards, so it naturally gets 3-2-1. If I delete this index from the CREATE TABLE statement, I get 1-2-3. For me this happens identically both in 10.3 and 10.4 May be some changes to server defaults, like optimizer_switch or use_stat_tables caused the optimizer to prefer a different plan in your case. I suspect for a large table with lots of rows the plan will be the same in 10.3 and 10.4, but for a small table when all plans have very similar (and small) costs you can, probably, expect this kind of instability. Regards, Sergei VP of MariaDB Server Engineering and security@mariadb.org