-----Original Message----- From: k...@rice.edu [mailto:k...@rice.edu] Sent: October 8, 2015 1:00 PM To: Carlo Cc: pgsql-performance@postgresql.org Subject: Re: [PERFORM] One long transaction or multiple short transactions?
On Thu, Oct 08, 2015 at 11:08:55AM -0400, Carlo wrote: > >> Sounds like a locking problem > > This is what I am trying to get at. The reason that I am not > addressing hardware or OS configuration concerns is that this is not > my environment, but my client's. The client is running my import > software and has a choice of how long the transactions can be. They > are going for long transactions, and I am trying to determine whether > there is a penalty for single long transactions over a configuration > which would allow for more successive short transactions. (keep in mind all reads and writes are single-row). > > There are other people working on hardware and OS configuration, and > that's why I can't want to get into a general optimization discussion > because the client is concerned with just this question. > On October 8, 2015 1:00 PM Ken wrote: > Hi Carlo, > Since the read/writes are basically independent, which is what I take your "single-row" comment to mean, by batching them you are balancing two > opposing factors. First, larger batches allow you to consolodate I/O and other resource requests to make them more efficient per row. Second, larger > batches require more locking as the number of rows updated grows. It may very well be the case that by halving your batch size that the system can > process them more quickly than a single batch that is twice the size. Just to clarify, one transaction of this type may take longer to commit than two successive transactions of half the size? -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
