Re: TOAST performance (was Re: [GENERAL] Delete Performance)

> The "delete" took about 2 seconds.  I then did it over with the
> 'value' being a 5K chunk of text, which according to octet_length
> got compressed to 3900 bytes.  (This'd require two rows in the TOAST
> table.)  This time the delete took 127 seconds.  I was expecting
> about a 3X penalty since we needed to delete three rows not one,
> but what I got was a 60X penalty.

Wow.  Can someone remind me why we take page images on delete?  We
aren't really writing anything special to the page except a transction
id.

> I've worried for some time that the decision to XLOG page images was
> costing us a lot more performance than could be justified...

Is it because we take a snapshot of the page before we write it in case
we only write part of the page?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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