Query cache unavailable for XtraDB tables

[Alexey Kopytko]

When
- using innodb_file_per_table and
- database name contains a dot
queries on tables in the database do not get saved into query cache.

A dot in the database directory name gets replaced by "@002e".

mysqld Ver 5.5.13-55-log for Linux on x86_64 (Percona Server (GPL), Release 20.4)

have_query_cache = YES
query_cache_limit = 1048576
query_cache_min_res_unit = 4096
query_cache_size = 133169152
query_cache_strip_comments = OFF
query_cache_type = ON
query_cache_wlock_invalidate = OFF

Qcache_free_blocks = 1
Qcache_free_memory = 133151344
Qcache_hits = 0
Qcache_inserts = 0
Qcache_lowmem_prunes = 0
Qcache_not_cached = 33751
Qcache_queries_in_cache = 0
Qcache_total_blocks = 1

[Alexey Kopytko (sanmai)]

A workaround is to dump/restore that database with a new name.

[Alexey Kopytov (akopytov)]

It's an upstream bug: http://bugs.mysql.com/bug.php?id=55556

[Stewart Smith (stewart)]

I'm going to close this as Won't Fix as it's a relatively broad category of bugs that would take a very long time to shake out. The converting back and forth between various table formats in MySQL works largely by accident and is a great source of obscure bugs. We'll naturally merge any upstream bug, but considering this is just to do with the query cache (which is a giant performance bottleneck for machines with greater than 1 CPU), it's not currently worth it for us to investigate a fix.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-2664