| From: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
|---|---|
| To: | Josh Berkus <josh(at)agliodbs(dot)com> |
| Cc: | "Sven R(dot) Kunze" <srkunze(at)tbz-pariv(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Reverse Key Index |
| Date: | 2015-02-26 12:37:04 |
| Message-ID: | 54EF1370.2000006@iki.fi |
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| Thread: | |
| Lists: | pgsql-performance |
On 02/26/2015 12:31 AM, Josh Berkus wrote:
> On 02/14/2015 10:35 AM, Sven R. Kunze wrote:
>> Thanks for the immediate reply.
>>
>> I understand the use case is quite limited.
>>
>> On the other hand, I see potential when it comes to applications which
>> use PostgreSQL. There, programmers would have to change a lot of code to
>> tweak existing (and more importantly working) queries to hash/reverse an
>> id column first. Using ORMs would make this change even more painful and
>> maybe even impossible.
>>
>> When reading
>> https://richardfoote.wordpress.com/2008/01/14/introduction-to-reverse-key-indexes-part-i/
>> carefully, it also seems to work with index scan partially in case of
>> equality comparisons.
>
> Seems like a good use for SP-GiST. Go for it!
A b-tree opclass that just compares from right-to-left would work just
as well, and perform better.
- Heikki
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