Re: PG slowdown

If you turn WAL logging off (via fsynch parameter in .conf), it is my
understanding that you will no longer log database updates, and will
therefore not be able to recover any uncommitted transactions in the event
of failure, (which seems contradictory to database practice).

Gut feel to me says your chckpoint_segments and timeout are too high.

On 7/12/06, Abu Mushayeed <amushayeed(at)hotmail(dot)com> wrote:
>
> Hello,
>
> My hardware
>
> CPU: Intel 3 GHZ X 4
> Memory: 9 GB
> LINUX
>
> My conf file are as follows:
>
> shared_buffers=10000
> wal_buffers=128
> vacuum_mem = 256000
> sort_mem=32768
> max_fsm_pages = 3000000
> max_fsm_relations = 32768
> checkpoint_segments = 2048
> checkpoint_timeout = 1800
> checkpoint_warning = 300
> effective_cache_size = 262144
> random_page_cost = 2
> default_statistics_target = 250
>
> Some of my queries that used to run within a minute, before I changed the
> "default_statistics_target" from 10 to 250, now runs for 20-30 minutes.
> Some
> queries did see improvement in their run time.
>
> I have two questions:
>
> 1. Why did the other queries slowdown? I tried to tune them, as their is a
> join between two tables and it reads all the rows, I forced it to do a seq
> scan rather than index scan but it quadrupled it run time. Why?
> 2. How can I disable the logging of updates? What are the pitfalls? When
> an
> update or insert happening there are lot of logging going on and the
> system
> writes messages like this "2006-07-11 10:08:54 [2330] LOG: checkpoints
> are
> occurring too frequently (182 seconds apart)
> HINT: Consider increasing the configuration parameter
> "checkpoint_segments"."
>
> Thank you for the help.
>
> Abu
>
>
>
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