| From: | Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com> |
|---|---|
| To: | Antonin Houska <ah(at)cybertec(dot)at> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Subject: | Re: Bitmap index scans use of filters on available columns |
| Date: | 2015-11-04 11:00:47 |
| Message-ID: | CAP-rdTYXmUT2rYOKHVfWeUaiPvkVR90jfLMUN9BQ24o-uRq2Rw@mail.gmail.com |
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| Lists: | pgsql-hackers |
2015-11-04 Antonin Houska <ah(at)cybertec(dot)at>:
> While prefix expression
>
> y like 'abc%'
>
> can be converted to
>
> y >= 'abc'
>
> (see expand_indexqual_opclause()), I'm not sure any kind of expansion is
> possible for '%abc%' which would result in a b-tree searchable condition.
I think the question is not about using the b-tree for checking the
condition, but about just retrieving the value for y from the index,
and just using that to check the condition before fetching the
corresponding tuple from the heap.
Nicolas
--
A. Because it breaks the logical sequence of discussion.
Q. Why is top posting bad?
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