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Re: PrivateRefCount (for 8.3)

From: "Simon Riggs" <simon(at)2ndquadrant(dot)com>
To: "Bruce Momjian" <bruce(at)momjian(dot)us>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,<pgsql-hackers(at)postgresql(dot)org>
Subject: Re: PrivateRefCount (for 8.3)
Date: 2006-11-27 20:11:18
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Mon, 2006-11-27 at 14:42 -0500, Bruce Momjian wrote:
> Simon Riggs wrote:
> > int8 still seems like overkjll. When will the ref counts go above 2 on a
> > regular basis? Surely refcount=2 is just chance at the best of times.
> > 
> > Refcount -> 2 bits per value, plus a simple overflow list? That would
> > allow 0,1,2 ref counts plus 3 means look in hashtable to find real
> > refcount.
> At two bits, would we run into contention for the byte by multiple
> backends?

No contention, its a private per-backend data structure. That's why we
want to reduce the size of it so badly.

  Simon Riggs             

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