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Re: Performance Enhancement/Fix for Array Utility Functions

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Mike Lewis <mikelikespie(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Daniel Farina <drfarina(at)acm(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Performance Enhancement/Fix for Array Utility Functions
Date: 2010-07-29 19:29:40
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Lists: pgsql-hackers
On Wed, Jul 28, 2010 at 1:20 AM, Mike Lewis <mikelikespie(at)gmail(dot)com> wrote:
>> > 1. As-is, it's a significant *pessimization* for small arrays, because
>> > the heap_tuple_untoast_attr_slice code does a palloc/copy even when one
>> > is not needed because the data is already not toasted.  I think there
>> > needs to be a code path that avoids that.
>> This seems like it shouldn't be too hard to fix, and I think it should be
>> fixed.
> Do you have any suggestions where to start?  I do agree that this should be
> fixed as well.   I don't have too much time to dedicate to this project.  I
> can try to put in some time this weekend though if it isn't looking too bad.

Perhaps you could check VARATT_IS_EXTENDED.  If that's true, then
slice it, but if it's false, then just use the original datum.  You
might want to wrap that up in a function rather than cramming it all
in the macro definition, though.

Robert Haas
The Enterprise Postgres Company

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