So, one problem I faced is thatSELECT * FROM INFORMATION_SCHEMA.TABLESis quite slow when I have thousands tables in TokuDB. How slow? For example…
select * from information_schema.tables limit 1000;...1000 rows in set (18 min 31.93 sec)
select*frominformation_schema.tableslimit1000; ... 1000rowsinset(18min31.93sec) |
This is very similar to what InnoDB faced a couple years back. InnoDB solved it by addingvariableinnodb_stats_on_metadata.
So what happens with TokuDB? There is an explanation from Rich Prohaska at Tokutek: “Tokudb has too much overhead for table opens. TokuDB does a calculation on the table when it is opened to see if it is empty. This calculation can be disabled when ‘tokudb_empty_scan=disabled‘. ”
So let’s see what we have withtokudb_empty_scan=disabled
select * from information_schema.tables limit 1000;...1000 rows in set (3 min 4.59 sec)
select*frominformation_schema.tableslimit1000; ... 1000rowsinset(3min4.59sec) |
An impressive improvement, but still somewhat slow. Tokutek promises a fix to improve it in the next TokuDB 7.2 release.
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