| From: | Pierre-Frédéric Caillaud <lists(at)boutiquenumerique(dot)com> |
|---|---|
| To: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: select single entry and its neighbours using direct-acess to index? |
| Date: | 2004-12-06 15:20:02 |
| Message-ID: | opsild7osscq72hf@musicbox |
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| Thread: | |
| Lists: | pgsql-general |
>> SELECT * FROM test WHERE (name='b' and name2>'a') OR (name>'b') ORDER BY
>> name,name2 ASC LIMIT 1;
> Write that WHERE clause instead as:
> WHERE name>='b' AND (name>'b' OR (name='b' AND name2>'a'))
> This is logically equivalent, but it gives the planner a better handle on
> how to use an index scan to satisfy the query.
I thought the planner had an automatic rewriter for these situations.
It'd be interesting to see an EXPLAIN ANALYZE output to see if it's indeed
rewritten.
>> SELECT * FROM test WHERE (name='b' and name2<'a') OR (name<'b') ORDER BY
>> name,name2 DESC LIMIT 1;
> That needs to be ORDER BY name DESC, name2 DESC (the direction indicator
> applies per-column and not to the output ordering). Same goes for the
> WHERE clause in this query as the previous one, too.
You're right, I screwed up !
Sorry ;)
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