Horton

Re: unlogged tables vs. GIST

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

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From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgresql.org
Date: 2010-12-17T19:48:58Z
Lists: pgsql-hackers

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  1. The GiST scan algorithm uses LSNs to detect concurrent pages splits, but

On 17.12.2010 21:32, Robert Haas wrote:
> I guess the question is whether it's right to conflate "table is
> unlogged" with "LSN is fake".  It's not immediately obvious to me that
> those concepts are isomorphic, although though the reverse isn't
> obvious to me either.

The buffer manager only needs to know if it has to flush the WAL before 
writing the page to disk. The flag just means that the buffer manager 
never needs to do that for this buffer. You're still free to store a 
real LSN there if you want to, it just won't cause any WAL flushes.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com