Ron,
On 6/8/06 11:49 AM, "Ron Mayer" <[EMAIL PROTECTED]> wrote:
> Experimental results here suggest that for larger tables Linux seems
> to detect a seq-scan and not bother caching. It's very reproducible
> for me here to do a reboot and not see the full speedup on a seq_scan
> until the third time I run a query.su
What you are seeing is the now infamous "Postgres writes a table one more
time after loading" behavior.
Simon Riggs once dug into it to find the root cause, and I no longer recall
exactly why, but after you've loaded data, the first seq scan will re-write
some large portion of the data while doing the initial scan. This wreaks
havoc on normal benchmarking practices.
Tom - can you explain what's going on with this? It seems to write more
than just the contents of the WAL, so it's not a flush of the WAL writes
AFAICT.
- Luke
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