Skip site navigation (1) Skip section navigation (2)

AW: TOAST & vacuum

From: Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at>
To: "'Bruce Momjian'" <pgman(at)candle(dot)pha(dot)pa(dot)us>, Jan Wieck <JanWieck(at)Yahoo(dot)com>
Cc: PostgreSQL HACKERS <pgsql-hackers(at)postgresql(dot)org>
Subject: AW: TOAST & vacuum
Date: 2000-07-27 08:21:47
Message-ID: 11C1E6749A55D411A9670001FA687963368032@sdexcsrv1.f000.d0188.sd.spardat.at (view raw or flat)
Thread:
Lists: pgsql-hackers
> >     TOAST  is now vacuum-safe. When needed, the toaster creates a
> >     second  heap  tuple,  containing  only  plain  or  compressed
> >     values.  This one is then returned by the heap access methods
> >     to  the  caller,  so  indices  will  never  contain  external
> >     references.
> > 
> >     The  changes  are  covered  by  #ifdef  TOAST_INDICES, so can
> >     easily be disabled at the time we have  file  versioning  and
> >     can recreate indices during vacuum.
> 
> Seems this has some performance advantages.  Un-toasting to traverse a
> btree index would be pretty slow.  This way, it is all in the index.

Yes, but it limits the key size. I was suggesting to Jan, that he reconsider
the "toast choice made for the heap tuple" for each index key, and store the
key 
compressed if it fits into 1/4 page.

I think the current setup (index toasting disabled) must be a lot better
performance 
wise than if you enable the current "index toasting" state of things.

Andreas


pgsql-hackers by date

Next:From: Karel ZakDate: 2000-07-27 08:26:00
Subject: Re: The query cache - first snapshot (long)
Previous:From: Zeugswetter Andreas SBDate: 2000-07-27 08:09:29
Subject: AW: AW: AW: AW: Vacuum only with 20% old tuples

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group