Re: EXPLAIN SELECT .. does not return

Tom Lane wrote:

>David Link <dlink(at)soundscan(dot)com> writes:
>
>
>>Certain SQL Queries, I believe those with many table joins, when run as
>>EXPLAIN plans, never return.
>>
>>
>
>I'd guess that one or all of these settings are excessive:
>
>
>
>>geqo_threshold = 14
>>from_collapse_limit = 13
>>join_collapse_limit = 13
>>
>>
>
>Keep in mind that the planning cost is exponential in these limits,
>eg geqo_threshold = 14 probably allows planning times about 14 times
>greater than geqo_threshold = 13.
>
>While I'm looking:
>
>
>
>>shared_buffers = 2000
>>
>>
>
>That seems extremely low for modern machines.
>
>
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>>sort_mem = 1048576
>>
>>
>
>That, on the other hand, is almost certainly way too high for a system-wide
>setting. You're promising you have 1Gb available for *each* sort.
>
>
>
>>max_fsm_pages = 100000
>>
>>
>
>And this way too low for a 100Gb database, unless most of the tables
>never see any UPDATEs or DELETEs.
>
>
>
>>wal_buffers = 800
>>
>>
>
>Seems a bit high, especially considering you have fsync disabled and
>thus there is no benefit whatever to buffering WAL.
>
>
>
>>commit_delay = 100
>>commit_siblings = 50
>>
>>
>
>Have you measured any benefit to having this turned on?
>
>All in all it looks like your configuration settings were chosen by
>throwing darts :-(
>
> regards, tom lane
>
>
>
Thanks for your reply, Tom. Different folks have made different
suggestions. Can you suggest more reasonable values for these? But
more importantly, do you think the problem I am having is due to these
configuration short comings?

Thanks much.
David