Re: restore time: sort_mem vs. checkpoing_segments

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Vivek Khera <khera(at)kcilink(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: restore time: sort_mem vs. checkpoing_segments
Date: 2003-09-16 05:19:00
Message-ID: 14070.1063689540@sss.pgh.pa.us
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Vivek Khera <khera(at)kcilink(dot)com> writes:
> Restore of a significanly big database (~19.8GB restored) shows nearly
> no time difference depending on sort_mem when checkpoint_segments is
> large. There are quite a number of tables and indexes. The restore
> was done from a pg_dump -Fc dump of one database.

I was just bugging Marc for some useful data, so I'll ask you too:
could you provide a trace of the pg_restore execution? log_statement
plus log_duration output would do it. I am curious to understand
exactly which steps in the restore are significant time sinks.

> I notice during the restore that the disk throughput triples during
> the checkpoint.

Hm, better make sure the log includes some indication of when
checkpoints happen.

regards, tom lane

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