Re: Toast space grows - Mailing list pgsql-performance
| From | Pavel Rotek |
|---|---|
| Subject | Re: Toast space grows |
| Date | |
| Msg-id | 3556c08c0803070611p542eb317vfaf9b783172b6c3@mail.gmail.com Whole thread Raw |
| In response to | Re: Toast space grows (Tom Lane <tgl@sss.pgh.pa.us>) |
| Responses |
Re: Toast space grows
Re: Toast space grows Re: Toast space grows |
| List | pgsql-performance |
2008/3/7, Tom Lane <tgl@sss.pgh.pa.us>:
well, this will be the main problem... But... do uncomitted trasactions affect toast space?
i'll set max_fsm_pages to 1 000 000. It should be enough and set autovacuum_naptime to 10 minutes. May it be?
I'll try to refactor the code... My application do following thing... long running jobs (for example long imports) are broken into series of short transactions to store snapshot of current state of long running job. Short transaction consist of
(begin tx, load previous log, do business action, append new log, flush, do business action, append new log, flush, ... do business action, append new log, flush, commit tx). Is it enough to avoid multiple "append new log, flush" in one short transaction and keep log changes for short transaction in the buffer (only one update of log attribute at the end of transaction)? From your answer probably not, but i ask for sure, it will be less work. Or store logs for each one partial transaction and concat all at the end of long running job??
"Pavel Rotek" <pavel.rotek@gmail.com> writes:
> No i do not mean long running transactions... Update of log entry (update of
> row in dataaction) is performed in series of short transactions, but during
> short transaction there is a lot of change log value, flush, change log
> value ,flush ..... change log value, flush actions (flush means perform
> flush operation via JDBC driver). I'm not sure if this flush affects toast
> space... Maybe this is the reason.
You mean that you build up the 5MB log entry by adding a few lines at a
time? That's going to consume horrid amounts of toast space, because
each time you add a few lines, an entire new toasted field value is
created.
well, this will be the main problem... But... do uncomitted trasactions affect toast space?
If you have to do it that way, you'll need very frequent vacuums on this
table (not vacuum full, as noted already) to keep the toast space from
bloating too much. And make sure you've got max_fsm_pages set high
enough.
If you can restructure your code a bit, it might be better to accumulate
log values in a short-lived table and only store the final form of a log
entry into the main table.
I'll try to refactor the code... My application do following thing... long running jobs (for example long imports) are broken into series of short transactions to store snapshot of current state of long running job. Short transaction consist of
(begin tx, load previous log, do business action, append new log, flush, do business action, append new log, flush, ... do business action, append new log, flush, commit tx). Is it enough to avoid multiple "append new log, flush" in one short transaction and keep log changes for short transaction in the buffer (only one update of log attribute at the end of transaction)? From your answer probably not, but i ask for sure, it will be less work. Or store logs for each one partial transaction and concat all at the end of long running job??
regards, tom lane
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