| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | Teodor Sigaev <teodor(at)sigaev(dot)ru> |
| Cc: | Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndQuadrant(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Pluggable Indexes |
| Date: | 2009-01-22 16:02:27 |
| Message-ID: | 20090122160227.GE4296@alvh.no-ip.org |
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| Lists: | pgsql-hackers |
Teodor Sigaev wrote:
>> What other constraints are there on such non-in-core indexex? Early (2005)
>> GIST indexes were very painful in production environments because vacuuming
>> them held locks for a *long* time (IIRC, an hour or so on my database) on
>> the indexes locking out queries. Was that just a shortcoming of the
>> implementation, or was it a side-effect of them not supporting recoverability.
>
> GiST concurrent algorithm is based on Log Sequence Number of WAL and that
> was the reason to implement WAL (and recoverability) first in GiST.
Hmm, IIRC it is based on a monotonically increasing number. It could
have been anything. LSN was just a monotonically increasing number that
would be available if WAL was implemented first (or in parallel).
Of course, there's no much point in an index that's easily corrupted, so
I understand the desire to implement WAL too -- I'm just pointing out
that concurrency could have been developed independently.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
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