| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Materialized views and unique indexes |
| Date: | 2013-03-08 03:32:16 |
| Message-ID: | 7982.1362713536@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Craig Ringer <craig(at)2ndquadrant(dot)com> writes:
> On 03/08/2013 10:55 AM, Michael Paquier wrote:
>> Also, as it is not mandatory for a unique index to be a constraint, I
>> think that we should block the creation of unique indexes too to avoid
>> any problems. Any suggestions?
> How much does the planner benefit from the implied constraint of a
> unique index? I almost wonder if it should be allowed at the cost of
> making the refresh of a matview that fails to comply an error.
A unique constraint can allow join elimination, so I'm thinking that
disallowing them is a bad idea (not to mention that it'd be a
considerable wart in the code to block them for matviews only).
regards, tom lane
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