Re: [GENERAL] Decreasing WAL size effects

2008-11-01 Thread Bruce Momjian
Tom Lane wrote: Greg Smith [EMAIL PROTECTED] writes: That pushes the problem of writing a little chunk of code that reads only the right amount of data and doesn't bother compressing the rest onto the person writing the archive command. Seems to me that leads back towards wanting to

Re: [GENERAL] Decreasing WAL size effects

2008-10-31 Thread Craig Ringer
Jason Long wrote: Greg Smith wrote: On Thu, 30 Oct 2008, Tom Lane wrote: The real reason not to put that functionality into core (or even contrib) is that it's a stopgap kluge. What the people who want this functionality *really* want is continuous (streaming) log-shipping, not

Re: [GENERAL] Decreasing WAL size effects

2008-10-31 Thread Craig Ringer
If Pg truncated the WAL files before calling archive_command, and would accept truncated WAL files on restore, that'd be really useful. On second thought - that'd prevent reuse of WAL files, or at least force the filesystem to potentially allocate new storage for the part that was

Re: [GENERAL] Decreasing WAL size effects

2008-10-31 Thread Magnus Hagander
On 31 okt 2008, at 02.18, Greg Smith [EMAIL PROTECTED] wrote: On Thu, 30 Oct 2008, Tom Lane wrote: The real reason not to put that functionality into core (or even contrib) is that it's a stopgap kluge. What the people who want this functionality *really* want is continuous (streaming)

Re: [GENERAL] Decreasing WAL size effects

2008-10-31 Thread Aidan Van Dyk
* Greg Smith [EMAIL PROTECTED] [081001 00:00]: The overhead of clearing out the whole thing is just large enough that it can be disruptive on systems generating lots of WAL traffic, so you don't want the main database processes bothering with that. A related fact is that there is a

Re: [GENERAL] Decreasing WAL size effects

2008-10-31 Thread Aidan Van Dyk
* Aidan Van Dyk [EMAIL PROTECTED] [081031 15:11]: Archiving 00010012 Archiving 00010013 Archiving 00010014 Archiving 00010017 Archiving 00010018 Archiving

Re: [GENERAL] Decreasing WAL size effects

2008-10-31 Thread Aidan Van Dyk
* Aidan Van Dyk [EMAIL PROTECTED] [081031 15:11]: How about something like the attached. It's been spun quickly, passed regression tests, and some simple hand tests on REL8_3_STABLE. It seem slike HEAD can't initdb on my machine (quad opteron with SW raid1), I tried a few revision in the

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Joshua D. Drake
On Wed, 2008-10-29 at 09:05 -0400, Greg Smith wrote: On Tue, 28 Oct 2008, Jason Long wrote: I also have to ship them off site using a T1 so setting the time to automatically switch files will just waste bandwidth if they are still going to be 16 MB anyway. The best way to handle

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Greg Smith
On Thu, 30 Oct 2008, Joshua D. Drake wrote: This reminds me yet again that pg_clearxlogtail should probably get added to the next commitfest for inclusion into 8.4; it's really essential for a WAN-based PITR setup and it would be nice to include it with the distribution. What is to be gained

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Jason Long
Greg Smith wrote: On Thu, 30 Oct 2008, Joshua D. Drake wrote: This reminds me yet again that pg_clearxlogtail should probably get added to the next commitfest for inclusion into 8.4; it's really essential for a WAN-based PITR setup and it would be nice to include it with the distribution.

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Kyle Cordes
Greg Smith wrote: there's no chance it can accidentally look like a valid segment. But when an existing segment is recycled, it gets a new header and that's it--the rest of the 16MB is still left behind from whatever was in that segment before. That means that even if you only write, say,

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Jason Long
Kyle Cordes wrote: Greg Smith wrote: there's no chance it can accidentally look like a valid segment. But when an existing segment is recycled, it gets a new header and that's it--the rest of the 16MB is still left behind from whatever was in that segment before. That means that even if

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Greg Smith
On Thu, 30 Oct 2008, Kyle Cordes wrote: It sure would be nice if there was a way for PG itself to zero the unused portion of logs as they are completed, perhaps this will make it in as part of the ideas discussed on this list a while back to make a more out of the box log-ship mechanism?

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Kyle Cordes
Greg Smith wrote: On Thu, 30 Oct 2008, Kyle Cordes wrote: It sure would be nice if there was a way for PG itself to zero the unused portion of logs as they are completed, perhaps this will make The overhead of clearing out the whole thing is just large enough that it can be disruptive on

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Gregory Stark
Greg Smith [EMAIL PROTECTED] writes: Now, it would be possible to have that less sensitive archive code path zero things out, but you'd need to introduce a way to note when it's been done (so you don't do it for a segment twice) and a way to turn it off so everybody doesn't go through that

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Christophe
On Oct 30, 2008, at 2:54 PM, Gregory Stark wrote: Wouldn't it be just as good to indicate to the archive command the amount of real data in the wal file and have it only bother copying up to that point? Hm! Interesting question: Can the WAL files be truncated, rather than zeroed,

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Kyle Cordes
Gregory Stark wrote: Greg Smith [EMAIL PROTECTED] writes: Wouldn't it be just as good to indicate to the archive command the amount of real data in the wal file and have it only bother copying up to that point? That sounds like a great solution to me; ideally it would be done in a way that

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Greg Smith
On Thu, 30 Oct 2008, Gregory Stark wrote: Wouldn't it be just as good to indicate to the archive command the amount of real data in the wal file and have it only bother copying up to that point? That pushes the problem of writing a little chunk of code that reads only the right amount of

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Tom Lane
Greg Smith [EMAIL PROTECTED] writes: That pushes the problem of writing a little chunk of code that reads only the right amount of data and doesn't bother compressing the rest onto the person writing the archive command. Seems to me that leads back towards wanting to bundle a contrib

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Greg Smith
On Thu, 30 Oct 2008, Tom Lane wrote: The real reason not to put that functionality into core (or even contrib) is that it's a stopgap kluge. What the people who want this functionality *really* want is continuous (streaming) log-shipping, not WAL-segment-at-a-time shipping. Sure, and that's

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Jason Long
Greg Smith wrote: On Thu, 30 Oct 2008, Tom Lane wrote: The real reason not to put that functionality into core (or even contrib) is that it's a stopgap kluge. What the people who want this functionality *really* want is continuous (streaming) log-shipping, not WAL-segment-at-a-time shipping.

Re: [GENERAL] Decreasing WAL size effects

2008-10-30 Thread Kyle Cordes
Jason Long wrote: Sure I would rather have synchronous WAL shipping, but if that is going to be a while or synchronous would slow down my applicaton I can get comfortably close enough for my purposes with some highly compressible WALs. I'm way out here on the outskirts (just a user with a

Re: [GENERAL] Decreasing WAL size effects

2008-10-29 Thread Joshua D. Drake
Jason Long wrote: I am planning on setting up PITR for my application. I also have to ship them off site using a T1 so setting the time to automatically switch files will just waste bandwidth if they are still going to be 16 MB anyway. *1. What is the effect of recompiling and reducing

Re: [GENERAL] Decreasing WAL size effects

2008-10-29 Thread Greg Smith
On Tue, 28 Oct 2008, Jason Long wrote: I also have to ship them off site using a T1 so setting the time to automatically switch files will just waste bandwidth if they are still going to be 16 MB anyway. The best way to handle this is to clear the unused portion of the WAL file and then

[GENERAL] Decreasing WAL size effects

2008-10-28 Thread Jason Long
I am planning on setting up PITR for my application. It does not see much traffic and it looks like the 16 MB log files switch about every 4 hours or so during business hours. I am also about to roll out functionality to store documents in a bytea column. This should make the logs roll