Re: Index Skip Scan

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>
Cc: Floris Van Nee <florisvannee(at)optiver(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, James Coleman <jtc331(at)gmail(dot)com>, Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Bhushan Uparkar <bhushan(dot)uparkar(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>
Subject: Re: Index Skip Scan
Date: 2020-05-13 22:55:47
Message-ID: CAH2-Wzm3OE+uPrFhg8HbW=Z+_ffF09nruLUag+H4EqZtNn+=Og@mail.gmail.com
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On Mon, Jan 20, 2020 at 5:05 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> You can add another assertion that calls a new utility function in
> bufmgr.c. That can use the same logic as this existing assertion in
> FlushOneBuffer():
>
> Assert(LWLockHeldByMe(BufferDescriptorGetContentLock(bufHdr)));
>
> We haven't needed assertions like this so far because it's usually it
> is clear whether or not a buffer lock is held (plus the bufmgr.c
> assertions help on their own).

Just in case anybody missed it, I am working on a patch that makes
nbtree use Valgrind instrumentation to detect page accessed without a
buffer content lock held:

https://postgr.es/m/CAH2-WzkLgyN3zBvRZ1pkNJThC=xi_0gpWRUb_45eexLH1+k2_Q@mail.gmail.com

There is also one component that detects when any buffer is accessed
without a buffer pin.

--
Peter Geoghegan

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