| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Seamus Abshere <seamus(at)abshere(dot)net> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Melvin Davidson <melvin6925(at)gmail(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Read-only tables to avoid row visibility check |
| Date: | 2016-02-22 22:45:28 |
| Message-ID: | 22147.1456181128@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Seamus Abshere <seamus(at)abshere(dot)net> writes:
> Being able to tell postgres that our table is "Read Only" has imaginary
> mystical properties for me, first and foremost being able to count
> against indexes without ever hitting the disk.
>> If the system is working properly then a READ ONLY table in fact should be able to use Index Only Scans without the hack of a DBA telling it that said table is READ ONLY.
> So this should happen already?
Yeah. Index-only scans will work if all (or at least most) of the table
hasn't been modified since the last VACUUM. If we had a READ ONLY
property, I do not think it would affect that logic at all; it would just
prevent future mods going forward. Which, as noted, you could already do
by revoking suitable privileges.
regards, tom lane
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