Re: Patch for seq scan & scan resistant bufmgr

This has been saved for the 8.4 release:

http://momjian.postgresql.org/cgi-bin/pgpatches_hold

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CK Tan wrote:
> Hi,
>
> I am submitting a patch for review that:
>
> 1. for small relation (smaller than 60% of bufferpool), use the
> current logic
> 2. for big relation:
> - use a ring buffer in heap scan
> - pin first 12 pages when scan starts
> - on consumption of every 4-page, read and pin the next 4-page
> - invalidate used pages of in the scan so they do not force out
> other useful pages
>
> 4 files changed:
> bufmgr.c, bufmgr.h, heapam.c, relscan.h
>
> If there are interests, I can submit another scan patch that returns
> N tuples at a time, instead of current one-at-a-time interface. This
> improves code locality and further improve performance by another
> 10-20%.
>
> For TPCH 1G tables, we are seeing more than 20% improvement in scans
> on the same hardware.
>
> ------------------------------------------------------------------------
> -
> ----- PATCHED VERSION
> ------------------------------------------------------------------------
> -
> gptest=# select count(*) from lineitem;
> count
> ---------
> 6001215
> (1 row)
>
> Time: 2117.025 ms
>
> ------------------------------------------------------------------------
> -
> ----- ORIGINAL CVS HEAD VERSION
> ------------------------------------------------------------------------
> -
> gptest=# select count(*) from lineitem;
> count
> ---------
> 6001215
> (1 row)
>
> Time: 2722.441 ms
>
>
> Suggestions for improvement are welcome.
>
> Regards,
> -cktan
> Greenplum, Inc.
>

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