Bug #105029 | Increased query time for "select count(distinct c)" | ||
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Submitted: | 24 Sep 2021 5:37 | Modified: | 24 Sep 2021 12:45 |
Reporter: | Souvik Dhargupta | Email Updates: | |
Status: | Duplicate | Impact on me: | |
Category: | MySQL Server | Severity: | S3 (Non-critical) |
Version: | 8.0. | OS: | Any |
Assigned to: | CPU Architecture: | Any |
[24 Sep 2021 5:37]
Souvik Dhargupta
[24 Sep 2021 12:45]
MySQL Verification Team
Hi Mr. Dhargupta, Thank you for your bug report. We discovered that there are already a number of verified bugs that are reporting the slowdown of read-only queries between 5.7 and 8.0. Hence, your report is a duplicate of the following verified bug : https://bugs.mysql.com/bug.php?id=94387 Thank you very much.
[24 Sep 2021 15:49]
Steinar Gunderson
Two questions: - Does this also happen if you set the collation to the same thing (presumably latin1_swedish_ci) on both versions, or is it about the default collation being changed to a more CPU-intensive one? - Does this also happen if you use VARCHAR instead of CHAR? (Nobody should really use CHAR anymore, including in sysbench. It is a relic from a time long since passed.)
[27 Sep 2021 12:25]
MySQL Verification Team
This is, indeed, a very important question, since lots of slowdowns are due to the change in the default character set.