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BUG #5000: Optimizer does not use function-based index for an order by

From: "Brian Ceccarelli" <ceccareb(at)talusmusic(dot)com>
To: pgsql-bugs(at)postgresql(dot)org
Subject: BUG #5000: Optimizer does not use function-based index for an order by
Date: 2009-08-20 20:30:56
Message-ID: 200908202030.n7KKUuNE034370@wwwmaster.postgresql.org (view raw or flat)
Thread:
Lists: pgsql-bugs
The following bug has been logged online:

Bug reference:      5000
Logged by:          Brian Ceccarelli
Email address:      ceccareb(at)talusmusic(dot)com
PostgreSQL version: 8.2.13
Operating system:   Linux
Description:        Optimizer does not use function-based index for an order
by
Details: 

Subject line says it all.
I have a function-based index on a large table.

select * 
  from net32_product_def 
 order by (f_squash_descr(descr::text))

create unique index net32_product_def_text_idx on net32_product_def (
f_squash_descr(descr) )

The explain plan says that Postgres always does a table scan instead of
using the index.   The table is 500,000 rows long, and the function
f_squash_descr() is a CPU-instensive operation.   What should come
instantly, takes 1 minute.

Responses

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Next:From: Greg StarkDate: 2009-08-20 21:54:56
Subject: Re: BUG #5000: Optimizer does not use function-based index for an order by
Previous:From: Brian CeccarelliDate: 2009-08-20 20:24:53
Subject: BUG #4999: select 'a' < 'A' is true, but should be false . . .

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