From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
---|---|
To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
Cc: | Dan Ports <drkp(at)csail(dot)mit(dot)edu>, "john(dot)okite(at)gmail(dot)org" <john(dot)okite(at)gmail(dot)org>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, anssi(dot)kaariainen(at)thl(dot)fi |
Subject: | Re: SSI patch version 8 |
Date: | 2011-01-13 15:02:21 |
Message-ID: | 4D2F13FD.3070009@enterprisedb.com |
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Lists: | pgsql-hackers |
On 13.01.2011 16:51, Kevin Grittner wrote:
> Right. As each tuple is read we need to ensure that there is a
> predicate lock to cover it. Since finer-grained locks can be
> combined into coarser-grained locks we need to start with the fine
> grained and move toward checking the coarser grains, to avoid
> missing a lock during promotion. So for each tuple we calculate a
> hash, find a partition, lock it, and lookup the tuple as a lock
> target. When that's not found we do the same thing for the page.
> When that's not found we do the same thing for the relation.
>
> But we acquired a relation lock up front, when we determined that
> this would be a heap scan, so we could short-circuit this whole
> thing if within the heapgettup_pagemode function we could determine
> that this was a scan of the whole relation.
That sounds simple enough. Add a boolean field to HeapScanDesc,
"rs_relpredicatelocked", and set it when you acquire the relation lock.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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