Обсуждение: Re: pgbench questions
[Cc:ed to hackers] From: nconway@klamath.dyndns.org (Neil Conway) Subject: pgbench questions Date: Sat, 13 Jul 2002 00:57:37 -0400 Message-ID: <20020713045736.GA9258@klamath.dyndns.org> > Hi, > > I was looking at doing some performance profiling on PostgreSQL, and > I had a few questions on pgbench. > > (1) Is there a reason you chose to use the TPC-B benchmark rather > than TPC-C or TPC-H, for example? Do you think there might be any > merit in converting pgbench to use TPC-H or AS3AP? Just easy to implement. Ideally pgbench should be able handle to several kinds of benchmarks (I don't have time to do that sigh...) BTW, TPC-H is very different from othe benchmarks. As far as I know, it focuses on Data Ware House. So TPC-H cannot be a replacement for TPC-B. > (2) At least in the current CVS version, the code to do a 'CHECKPOINT' > after creating a table has been #ifdef'ed out. Why is that? That is not after creation of a table, but while creating it, which is not necessary any more since Tom has fix the growth of WAL logs. > (3) Several people (Rod Taylor, Tom Lane, myself, perhaps others) have > noticed that the results obtained from pgbench can be somewhat > inconsistent (i.e. can vary between runs quite a bit). > > Have you found this to be the case in your own experience? > > Do you have any suggestions on how pgbench can be made more > consistent (either through special benchmarking procedures, or > through a change to pgbench) I believe it's a common problem with benchmark programs. I think Tom or Jan has posted a good summary to hackers list showing how to get a consistent result with pgbench. -- Tatsuo Ishii
On Sat, 2002-07-13 at 02:25, Tatsuo Ishii wrote: > > (2) At least in the current CVS version, the code to do a 'CHECKPOINT' > > after creating a table has been #ifdef'ed out. Why is that? > > That is not after creation of a table, but while creating it, which is > not necessary any more since Tom has fix the growth of WAL logs. > Tatsou: Could you or Tom give me some background on what this change was about? Is this something recent, or would it have been in CVS about a month ago? I can't see any reason to force a checkpoint after CREATE TABLE, but it would be interesting to know why it was done before. ;John Nield -- J. R. Nield jrnield@usol.com
J. R. Nield wrote: > On Sat, 2002-07-13 at 02:25, Tatsuo Ishii wrote: > > > (2) At least in the current CVS version, the code to do a 'CHECKPOINT' > > > after creating a table has been #ifdef'ed out. Why is that? > > > > That is not after creation of a table, but while creating it, which is > > not necessary any more since Tom has fix the growth of WAL logs. > > > > Tatsou: > > Could you or Tom give me some background on what this change was about? > Is this something recent, or would it have been in CVS about a month > ago? > > I can't see any reason to force a checkpoint after CREATE TABLE, but it > would be interesting to know why it was done before. 7.1.0 had a problem with WAL file growth. This was fixed in 7.1.2 or 7.1.3 so checkpoint is not required anymore. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000+ If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania19026