Re: [HACKERS] Visibility map and hint bits

2011-05-06 Thread Merlin Moncure
On Thu, May 5, 2011 at 2:20 PM, Merlin Moncure wrote: > On Thu, May 5, 2011 at 2:00 PM, Kevin Grittner > wrote: >> Merlin Moncure wrote: >> >>> a small cache that remembers the commit/cancel status of recently >>> seen transactions. >> >> How is that different from the head of the clog SLRU? > >

Re: [HACKERS] Visibility map and hint bits

2011-05-05 Thread Merlin Moncure
On Thu, May 5, 2011 at 2:00 PM, Kevin Grittner wrote: > Merlin Moncure wrote: > >> a small cache that remembers the commit/cancel status of recently >> seen transactions. > > How is that different from the head of the clog SLRU? several things: *) any slru access requires lock (besides the lock

Re: [HACKERS] Visibility map and hint bits

2011-05-05 Thread Kevin Grittner
Merlin Moncure wrote: > a small cache that remembers the commit/cancel status of recently > seen transactions. How is that different from the head of the clog SLRU? -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www

Re: [HACKERS] Visibility map and hint bits

2011-05-05 Thread Merlin Moncure
On Thu, May 5, 2011 at 1:34 PM, Bruce Momjian wrote: > Merlin Moncure wrote: >> On Thu, May 5, 2011 at 11:59 AM, Bruce Momjian wrote: >> > There has been a lot of recent discussion about the visibility map (for >> > index-only scans) and hint bits (trying to avoid double-writing a >> > table). >>

Re: [HACKERS] Visibility map and hint bits

2011-05-05 Thread Robert Haas
On Thu, May 5, 2011 at 12:59 PM, Bruce Momjian wrote: > I wonder if we could fix both of these at the same time.  Once the > visibility map is reliable, can we use that to avoid updating the hint > bits on all rows on a page? I don't think so. There are two problems: 1. If there is a long-runni

Re: [HACKERS] Visibility map and hint bits

2011-05-05 Thread Bruce Momjian
Merlin Moncure wrote: > On Thu, May 5, 2011 at 11:59 AM, Bruce Momjian wrote: > > There has been a lot of recent discussion about the visibility map (for > > index-only scans) and hint bits (trying to avoid double-writing a > > table). > > I still think a small tqual.c maintained cache of hint bi

Re: [HACKERS] Visibility map and hint bits

2011-05-05 Thread Merlin Moncure
On Thu, May 5, 2011 at 11:59 AM, Bruce Momjian wrote: > There has been a lot of recent discussion about the visibility map (for > index-only scans) and hint bits (trying to avoid double-writing a > table). I still think a small tqual.c maintained cache of hint bits will effectively eliminate hint