Re: 9.2 and index only scans
| От | Chris Travers |
|---|---|
| Тема | Re: 9.2 and index only scans |
| Дата | |
| Msg-id | CAKt_Zfv+Y5T2eW6t1UV2zoZRd42yKbiWCiiBBdfE2hBFN7Y1ig@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: 9.2 and index only scans (Craig Ringer <ringerc@ringerc.id.au>) |
| Список | pgsql-general |
On Tue, Aug 28, 2012 at 6:04 AM, Craig Ringer <ringerc@ringerc.id.au> wrote:
On 08/28/2012 05:51 PM, Thomas Kellerer wrote:Wow. Doesn't that mean that indexes are insanely expensive to update, since each index (and possibly also the table its self) needs updating?Martijn van Oosterhout, 28.08.2012 10:02:I'm not sure how oracle avoids the same issues:
- The index has no visibility information, so you can't tell if an
index entry refers to a row you can actually see in your session.
The visibility map might help here in the future.
In Oracle an index (entry) has the information about transactional
visibility.
I was thinking of read performance. But it might be a case where the global optimization might be worth the local cost. I don't know.
Best Wishes,
Chris Travers
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