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* Performance of IN (...) vs. = ANY array[...]
@ 2006-09-15 19:12 Benjamin Minshall <minshall@intellicon.biz>
0 siblings, 1 reply; 2+ messages in thread
From: Benjamin Minshall @ 2006-09-15 19:12 UTC (permalink / raw)
To: pgsql-performance
Greetings:
I'm running 8.1.4, and have noticed major differences in execution time
for plpgsql functions running queries that differ only in use of an
array such as:
slower_function( vals integer[] )
[query] WHERE id = ANY vals;
faster_function( vals integer[] )
vals_text := array_to_string( vals, ',' )
EXECUTE '[query] WHERE id IN (' || vals_text || ')';
In general, there are about 10 integers in the lookup set on average and
50 max.
What are the advantages or disadvantages of using arrays in this
situation? The = ANY array method makes plpgsql development cleaner,
but seems to really lack performance in certain cases. What do you
recommend as the preferred method?
Thanks for your comments.
--
Benjamin Minshall <minshall@intellicon.biz>
Senior Developer -- Intellicon, Inc.
http://www.intellicon.biz
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* Re: Performance of IN (...) vs. = ANY array[...]
@ 2006-09-15 20:19 Tom Lane <tgl@sss.pgh.pa.us>
parent: Benjamin Minshall <minshall@intellicon.biz>
0 siblings, 0 replies; 2+ messages in thread
From: Tom Lane @ 2006-09-15 20:19 UTC (permalink / raw)
To: Benjamin Minshall <minshall@intellicon.biz>; +Cc: pgsql-performance
Benjamin Minshall <minshall@intellicon.biz> writes:
> What are the advantages or disadvantages of using arrays in this
> situation? The = ANY array method makes plpgsql development cleaner,
> but seems to really lack performance in certain cases.
In existing releases, the form with IN (list-of-scalar-constants)
can be optimized into indexscan(s), but = ANY (array) isn't.
8.2 will treat them equivalently (in fact, it converts IN (...) to
= ANY (ARRAY[...]) !). So depending on your time horizon, you might
wish to stick with whichever is cleaner for your calling code.
regards, tom lane
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2006-09-15 19:12 Performance of IN (...) vs. = ANY array[...] Benjamin Minshall <minshall@intellicon.biz>
2006-09-15 20:19 ` Tom Lane <tgl@sss.pgh.pa.us>
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