Re: How to rewrite query

[Martin Skold]

Hi!

Try:
set engine_condition_pushdown = on;
explain select ip from ipaddr
 where pool='INTERNET' and stype='S' and ls_id=3 and allocated is null
 limit 1;
to see if you can push the predicates to improve performance.

BR
-- Martin

Mindaugas wrote:
>
>  Hello,
>
>  For the Radius server we're using MySQL cluster and the following 
> query looks too slow:
>
> select ip from ipaddr
>  where pool='INTERNET' and stype='S' and ls_id=3 and allocated is null
>  limit 1;
>
>  Table ipaddr is small (~6MB, 38000 records). Fields in WHERE clause 
> have few values and no indexes:
>  - pool: 2 distinct values;
>  - stype: 6 distinct values;
>  - ls_id: 5 distinct values;
>  - allocated is null for ~30000 of records.
>
>  Table type is NDB. If I change it to MEMORY everything starts to fly.
>
>  Of course there are a lot of updates to ipaddr table too. For every 
> select there are 3 updates. But updates are of type "update something 
> where ip=ipaddr" and ipaddr is unique key.
>
>  What can cause slowdown in NDB case? Table is small and is in memory 
> (5.0 cluster). Maybe I can rewrite it in some better form for such case?
>  MySQL setting are basically default. I did not find something in 
> documentation about improving performance of NDB engine tables.
>  Maybe increase read_buffer_size which is currently the default 128k? 
> Server has 4GB of memory and runs x86_64 version of CentOS4 Linux.
>
>  Thanks,
>
>  Mindaugas
>
>


-- 
Martin Sköld, Ph.D 
Software Engineer
MySQL AB, www.mysql.com
Office: [phone]