We are using Percona Server + TokuDB engine extensively in Percona Cloud Tools and getting real usage operational experience with this engine. So I want to share some findings we came across, in hope it may help someone in their work with TokuDB.
So, one problem I faced is that SELECT * FROM INFORMATION_SCHEMA.TABLES is quite slow when I have thousands tables in TokuDB. How slow? For example…
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select * from information_schema.tables limit 1000;<br>...<br>1000 rows in set (18 min 31.93 sec)<br> |
This is very similar to what InnoDB faced a couple years back. InnoDB solved it by adding variable innodb_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 with tokudb_empty_scan=disabled
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select * from information_schema.tables limit 1000;<br>...<br>1000 rows in set (3 min 4.59 sec)<br> |
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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