Horton

Re: unlogged tables vs. GIST

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@postgresql.org
Date: 2010-12-17T19:22:35Z
Lists: pgsql-hackers

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

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> writes:
> On 17.12.2010 21:07, Tom Lane wrote:
>> IIUC, the problem is that the bufmgr might think that a GIST NSN is an
>> LSN that should affect when to force out a dirty buffer?  What if we
>> taught it the difference?  We could for example dedicate a pd_flags
>> bit to marking pages whose pd_lsn isn't actually an LSN.

> I'm not very fond of expanding buffer manager's knowledge of the page 
> layout. How about a new flag in the buffer desc, BM_UNLOGGED?

That could work too, if you can explain how the flag comes to be set
without a bunch of ugliness all over the system.  I don't want callers
of ReadBuffer to have to supply the bit for example.

			regards, tom lane