Re: SQL compatibility reminder: MySQL vs PostgreSQL

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От Robert Haas
Тема Re: SQL compatibility reminder: MySQL vs PostgreSQL
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Msg-id 603c8f071003080644t2400ef0r4263b0ac12e3cec6@mail.gmail.com
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Ответ на Re: SQL compatibility reminder: MySQL vs PostgreSQL  (Marko Tiikkaja <marko.tiikkaja@cs.helsinki.fi>)
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On Mon, Mar 8, 2010 at 4:58 AM, Marko Tiikkaja
<marko.tiikkaja@cs.helsinki.fi> wrote:
> On 2010-03-08 11:47 +0200, Pierre C wrote:
>>> As far as I can tell, we already do index skip scans:
>>
>> This feature is great but I was thinking about something else, like SELECT
>> DISTINCT, which currently does a seq scan, even if x is indexed.
>>
>> Here is an example. In both cases it could use the index to skip all
>> non-interesting rows, pulling only 69 rows from the heap instead of 120K.
>
> Oh, this is what I believe MySQL calls "loose index scans".  I'm
> actually looking into this as we speak, but there seems to be a
> non-trivial amount of work to be done in order for this to work.

We should probably have a TODO for this, if we don't already.

...Robert


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