From: | Andreas Joseph Krogh <andreak(at)officenet(dot)no> |
---|---|
To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Covering Indexes |
Date: | 2012-06-28 12:56:36 |
Message-ID: | 4FEC5484.1090908@officenet.no |
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Lists: | pgsql-hackers |
On 06/28/2012 02:16 PM, David E. Wheeler wrote:
> Hackers,
>
> Very interesting design document for SQLite 4:
>
> http://www.sqlite.org/src4/doc/trunk/www/design.wiki
>
> I'm particularly intrigued by "covering indexes". For example:
>
> CREATE INDEX cover1 ON table1(a,b) COVERING(c,d);
>
> This allows the following query to do an index-only scan:
>
> SELECT c, d FROM table1 WHERE a=? AND b=?;
>
> Now that we have index-only scans in 9.2, I'm wondering if it would make sense to add covering index support, too, where additional, unindexed columns are stored alongside indexed columns.
>
> And I wonder if it would work well with expressions, too?
>
> David
This is analogous to SQL Server's "include" :
|CREATE NONCLUSTERED INDEX my_idx|
|ON my_table (status)|
|INCLUDE (someColumn, otherColumn)|
Which is useful, but bloats the index.
--
Andreas Joseph Krogh<andreak(at)officenet(dot)no> - mob: +47 909 56 963
Senior Software Developer / CEO - OfficeNet AS - http://www.officenet.no
Public key: http://home.officenet.no/~andreak/public_key.asc
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