From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | John Gray <jgray(at)azuli(dot)co(dot)uk> |
Cc: | pgsql-patches(at)postgresql(dot)org |
Subject: | Re: Efficient slicing/substring of TOAST values (for comment) |
Date: | 2002-02-22 18:52:00 |
Message-ID: | 200202221852.g1MIq0n04974@candle.pha.pa.us |
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Thread: | |
Lists: | pgsql-patches |
John, do you have an updated version of this patch that is ready to be
applied to 7.3?
---------------------------------------------------------------------------
John Gray wrote:
> Hi all,
>
> I attach a patch which adds access routines for efficient extraction of
> parts of TOAST values.
>
> The principal additions are two routines in tuptoaster.c,
> heap_tuple_untoast_attr_slice and toast_fetch_datum_slice. The latter
> uses extra index scankeys to retrieve only the TOAST chunks which
> contain the requested substring. This will provide a performance benefit
> if you repeatedly extract small portions (e.g. file headers) from
> TOASTed values, as only one or two chunks will need to be fetched. This
> function is only invoked for external, uncompressed storage.
>
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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