| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Composite Datums containing toasted fields are a bad idea(?) |
| Date: | 2014-04-21 15:17:17 |
| Message-ID: | 20140421151717.GC14024@alap3.anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers |
Hi,
On 2014-04-20 15:38:23 -0400, Tom Lane wrote:
> Some poking around with oprofile says that much of the added time is
> coming from added syscache and typcache lookups, as I suspected.
>
> I did some further work on the patch to make it possible to cache
> the element tuple descriptor across calls for these two functions.
> With the attached patch, the first test case comes down to about 335 ms
> and the second to about 1475 ms (plpgsql is still leaving some extra
> cache lookups on the table). More could be done with some further API
> changes, but I think this is about as much as is safe to back-patch.
I unfortunately haven't followed this in detail, but shouldn't it be
relatively easily to make this even cheaper by checking for
HEAP_HASEXTERNAL? If it's not set we don't need to iterate over the
composite's columns, right?
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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