On Sat, May 25, 2013 at 3:08 AM, German Becker <german.becker@gmail.com> wrote: > Thanks Amit, I understand now. Is there a way to know/predict how many > prealocated segments will there be in a certain moment? What does it deppend > on?
Upthread, Fujii Masao-san suggested what might have happened that caused these pre-allocated segments to be created. To quote him:
"WAL recycling is performed by checkpoint. Checkpoint always checks whether there are WAL files no longer required for crash recovery, IOW, WAL files which were generated before the prior checkpoint happened, and then if they are found, checkpoint tries to recycle them."
If you are still using the same values as during this observation, could you provide values for these postgresql.conf parameters: checkpoint_segments, checkpoint_timeout, wal_keep_segments?
-- Amit Langote
Amit,
Frist, thanks for your help and your interest. I (think) I understand how checkpoint /wal segment work. What I didn't understand from the documentation is the possibility of segments being prealocated. I thought that the WAL segment with the higher sequence number is the one being written at present time, as opposed to a segment allocated to be written in the future. If you could clarify this point to me, that would be great.
Here are the parameters related to checkpoint
For "restore" config
checkpoint_segments = 256 # in logfile segments, min 1, 16MB each