[GENERAL] Large Object table data file does not have expected size
I am a little bit confused by the following effect. For test reasons I insert about 10 large objects into the database. Each has a size of 10240 Bytes (10K). So the expected size of the large object datafile should be at least 102400 Bytes (about 976MB) just to hold the large objects. But the according data file is much smaller than that. If I query the large objetcs from psql all data seems to be there (i just randomly picked out some large objects). I first thought there was a bug in my test program (not all large objetcs are inserted), but I couldn't find one. Also this was unlikely, since I always insert the same binary data (for the large objetc) in a simple loop. Has anyone an idea why the datafiles are much smaller than I expect them to be? Thanks, Andreas. - This mail sent through IMP: http://horde.org/imp/ ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
[GENERAL] Is it possible to change the wal file size?
Can I change the size of a wal file, and if so where can I change this? I'd like to set the value to bigger value than 16MB. Thanks, Andreas. - This mail sent through IMP: http://horde.org/imp/ ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [GENERAL] Is it possible to change the wal file size?
> You can not change the size but you can increase the number of WAL files > used. > See postgresql.conf. > > Setting it too high does not achieve anything though. You need to have enough > > disk bandwidth to make use of 200MB WAL logs. I want write a lot of data (large objetcs) without any interruptions. So I already increased the number of checkpoint_segments to a higher value. But this did not help since I still get interruptions in writing data, when a new log file is created. - This mail sent through IMP: http://horde.org/imp/ ---(end of broadcast)--- TIP 6: Have you searched our list archives? http://archives.postgresql.org
Re: [GENERAL] Checkpoint question
Zitat von Tom Lane <[EMAIL PROTECTED]>: > A checkpoint pushes out all unwritten data since the last checkpoint. > So yeah, it stands to reason that if you increase the time between > checkpoints, each checkpoint will take longer. Whether this is really > a problem is not clear --- the checkpoint is happening in background > after all. Why should you care how long it takes? > > regards, tom lane > > What I want to do, is to write a lot of data in the database over a longer period (assume 1 hour or longer) with constant data rates - I am trying to use Postgres to store measurement data. When I only had a few checkpoint_segments (3 I think), I always got an interruption when the database was checkpointing (what took about 3 seconds). So I increased the checkpoint_segments and the pauses went away. But now I think if I reach the segments limit again, I will get even bigger pauses (of course at some point in the time a checkpoint has to be performed). By the way, if you say, checkpointing is happening in the background, I don't know what causes the pauses. - This mail sent through IMP: http://horde.org/imp/ ---(end of broadcast)--- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
Re: [GENERAL] Checkpoint question
Zitat von Tom Lane <[EMAIL PROTECTED]>: > Probably insufficient disk bandwidth. If you have two drives available, > try putting the WAL files (pg_xlog directory) on a different drive from > the data files. Assuming you have adequate RAM, updates will be mainly > limited by writes to WAL, while checkpoint doesn't touch WAL and is all > about pushing data from RAM to the data files. So with a proper drive > split, checkpoint really shouldn't affect update rate at all. (It could > affect the time for SELECT queries, if they need to fetch data that > isn't in RAM, but that didn't seem to be your complaint.) > > regards, tom lane > > ---(end of broadcast)--- > TIP 9: the planner will ignore your desire to choose an index scan if your > joining column's datatypes do not match > > Can you specify more exactly what you mean with update rate? I moslty perform inserts on the database (is that what you mean?). Also I do not understand, why checkpoint does not touch WAL, but RAM. I thought that a checkpoint reads the information from the WAL-Files and pushes these information to the data files. Thanks Andreas - This mail sent through IMP: http://horde.org/imp/ ---(end of broadcast)--- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
