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Re: unlogged tables vs. GIST

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: unlogged tables vs. GIST
Date: 2013-01-15 20:56:04
Message-ID: CA+TgmoZFiLnAVoZ7N7FeZNrUXk2n7hKiPZydXeZaQrqPHAUxcg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, Jan 15, 2013 at 1:58 PM, Heikki Linnakangas
<hlinnakangas(at)vmware(dot)com> wrote:
>> I think what Heikki had in mind was that the copy in the index would be
>> the authoritative one, not some image in shared memory.  This'd imply
>> dirtying the root page on every insert, as well as increased contention
>> for the root page, so it might have performance problems.
>
> Not every insert, just every split. Which might still be a performance
> problem, but an order of magnitude smaller.

I think that might be acceptable from a performance point of view -
after all, if the index is unlogged, you're saving the cost of WAL -
but I guess I still prefer a generic solution to this problem (a
generalization of GetXLogRecPtrForTemp) rather than a special-purpose
solution based on the nitty-gritty of how GiST uses these values.
What's the difference between storing this value in pg_control and,
say, the OID counter?

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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