Re: query plan question, nested loop vs hash join

2014-10-05 21:57 GMT+03:00 Andrey Lizenko <lizenko79(at)gmail(dot)com>:

> Increasing of 'effective_cache_size' leads to similar thing with
> mergejoin,
> other options (work_mem, shared_buffers. etc) do not change anything.
>

I think increasing `work_mem` should have effects, as plan with `Nested
Loop` is using disk-based sort.
Increase it till you'll stop seeing `external sort` in the EXPLAIN output.
Something like '10MB' should do.

Also, it'd be handy if you could provide `EXPLAIN (analyze, buffers)`
output along with the results of these queries:

SELECT name,setting,source FROM pg_settings WHERE name ~ 'cost' AND NOT
name ~ 'vacuum';
SELECT name,setting,source FROM pg_settings WHERE NOT source IN
('default','override');

And describe your setup: what OS? how much RAM? what kind of disks? RAID?

--
Victor Y. Yegorov