| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru> |
| Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: WIP: Covering + unique indexes. |
| Date: | 2015-12-03 01:03:56 |
| Message-ID: | CA+TgmoYGPcKVtySqs1OFbfkpOt+mtXiRtCj-vqQ_d4swxNXGCg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Dec 1, 2015 at 7:53 AM, Anastasia Lubennikova
<a(dot)lubennikova(at)postgrespro(dot)ru> wrote:
> If we don't need c4 as an index scankey, we don't need any btree opclass on
> it.
> But we still want to have it in covering index for queries like
>
> SELECT c4 FROM tbl WHERE c1=1000; // uses the IndexOnlyScan
> SELECT * FROM tbl WHERE c1=1000; // uses the IndexOnlyScan
>
> The patch "optional_opclass" completely ignores opclasses of included
> attributes.
OK, I don't get it. Why have an opclass here at all, even optionally?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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