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Re: More fun with GIN lossy-page pointers

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>, Teodor Sigaev <teodor(at)sigaev(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: More fun with GIN lossy-page pointers
Date: 2010-08-01 01:35:51
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Excerpts from Tom Lane's message of sáb jul 31 09:57:13 -0400 2010:

> So far as I can see, it's impossible to handle this situation when
> examining only one TID per stream with no lookahead.  Choosing to
> advance the second stream would obviously fail in many other cases,
> so there is no correct action.  The only reasonable way out is to
> forbid the case --- that is, decree that a keystream may *not*
> contain both lossy and nonlossy pointers to the same page.

Would it make sense to order the streams differently?  I mean, what if
whole-page pointers in the lossy stream are processed before regular ones?
(I am thoroughly unfamiliar with this stuff, so forgive me if I've
gotten the concepts and terminology all wrong)

Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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