| From: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Subject: | Re: "Value locking" Wiki page |
| Date: | 2014-10-01 10:58:04 |
| Message-ID: | 542BDE3C.7040802@vmware.com |
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| Lists: | pgsql-hackers |
On 10/01/2014 01:50 PM, Simon Riggs wrote:
> On 1 October 2014 10:44, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> wrote:
>
>> I didn't realize that "promise index tuples" were even seriously discussed.
>> I guess that can be made to work, too, although I don't see the point. It
>> wouldn't work with GiST indexes, for the same reasons as page-level locking
>> won't work (a tuple can legally be inserted anywhere in a GiST index - it
>> just degrades the index making searching more expensive). And lossy GiST
>> opclasses are a problem too.
>
> GiST doesn't support unique indexes, so it is not in any way a problem.
GiST supports exclusion constraints. That is one of the main reasons I
want to do promise tuples, instead of locking within the indexam: to
support this feature with exclusion constraints.
- Heikki
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