- Bug #100000 - "Provide an index hint that only affects the choice of index for NL join". This nice feature request was added by former optimizer developer in MySQL, Øystein Grøvlen. Hundreds of other feature requests are waiting for the attention both from the MySQL Verification Team and from developers, so good to see a feature request getting the number that nobody ever forget!
- Bug #99994 - "Index range scan is chosen where table scan takes 40% less time". Clear and simple bug report that relies on the world sample database.
- Bug #99995 - "Histogram is not used for filtering estimate when index is disabled".
- Bug #99996 - "Prefer histogram over index statistics when eq_range_index_dive_limit is exceeded". This was verified as a feature request.
- Bug #99997 - "Range estimates are usually off by a factor of 2 for large ranges". It was declared a duplicate of older bug report I am also subscribed to, Bug #73386 - "For ranges, innodb doubles estimates, or caps estimates to half the table". See also this MariaDB bug report, MDEV-19424 - "InnoDB's records_in_range estimates are capped at about 50%", and links from it for a lot of related discussions. Let's wait and see what vendor resolves this faster...
The other report, Bug #99998 - "For large ranges, the range estimate will never exceed 50%", is probably also a duplicate of the same old bug.
- Bug #99999 - "EXPLAIN FORMAT=TREE does not show cost/rows for semijoin materialization". Yet another nice and clear bug report.
Now back to some older bugs I've subscribed to over last 4 weeks:
- Bug #99791 - "MySQL 8 orphaned table due to unchecked non-existent row format check." As reported by Marc Reilly, tables created in versions < MySQL 8 which use row_format COMPRESSED or REDUNDANT, where row_format is not set explicitly in the Table DDL allow users to create un-prefixed indexes on fields which exceed the maximum column size of 767 bytes. Upgrading to MySQL 8 do nothing with these tables, but as soon as new index is added and reboot happens, such a table becomes inaccessible. What a surprise!
- Bug #99794 - "MySQL 57 client is inefficient at bulkloads/binlog replay". In this bug report Marc Reilly basically asks to back port the fix from MySQL 8.0.13.
- Bug #99800 - "ps_truncate_all_tables() does not work in super_read_only mode". This regression bug was reported by Lalit Choudhary.
- Bug #99805 - "mysql async client is incomplete". There is no way to determine file descriptor state (should it block on read or write), so it is impossible to use it in asynchronous contexts without busy looping. This bug report by Domas Mituzas was used in one discussion as an argument that MySQL bugs database still gets proper attention from MySQL engineers. It's truly so.
- Bug #99892 - "initialize with innodb_page_size=4096 gets "Specified key was too long" errors". This is a regression vs 5.7 (without a tag). As Mark Callaghan found out, one can not initialize MySQL 8 instance without errors with such a small innodb_page_size.
- Bug #99924 - "The record per key value from InnoDB is not suitable when n_diff is zero". As reported by Ze Yang, due to lack of locking when server reads the innodb_rec_per_key, the n_diff value may be 0 (not set) while the table->stat_n_rows is > 0. As a result (see great comment by Øystein Grøvlen), if a table object is opened during the recalculation of statistics, the rec_per_key for a column/index may be quite misleading. It will be interpreted as all rows have the same value, and the index will probably not be chosen for any non-covering scans. There is a patch suggested (to set rec_per_key to 1 or 10 in such case), as well as other suggestion to set the value REC_PER_KEY_UNKNOWN. Useful reading!
- Bug #99933 - "In-memory hash join will only use two-thirds of join buffer". Yet another bug report related to hash joins from Øystein Grøvlen, with a fix suggested. See also his Bug #99934 - "Hash join adds columns to the hash table that is not needed." There is a lot of work ahead to improve the implementation of this new feature in MySQL 8.
- Bug #99935 - "innodb_doublewrite_files is not correct when innodb_buffer_pool_size > 1G". Just 2 files are created instead of 16 according to the manual. This bug was reported by Satya Bodapati.
- Bug #99943 - "Hash join does not work for Semijoin and Antijoin". This bug report from Tibor Korocz was "Verified", but later comments suggest that it's more like wrong expectations/interpretation of cases when the feature has to be used (it is supposed to be used instead of BNL, but not instead of semijoin materialization and subquery materialization). Let's wait and see how it ends up...
- Bug #99966 - "Switching to use NUMA-SMART Counter for statistical counters". Great bug report from Krunal Bauskar, with a patch suggested. I hope to get a NUMA system one day myself to understand the challenges and performance problems there better.
Percona had recently started to blog about bugs, so I am sure they will keep an eye and share lists of important bugs on a regular basis. They should really care more than I do these days.