Re: BUG #9161: wal_writer_delay is limited to 10s

Hi Jeff,

>> > That only happens if an 8 KB boundary has been crossed. Depending on
>> > how
>> > big the records are that he is inserting, you can fit a lot of them in 8
>> > KB. If the records are small, or the table us unlogged so only commit
>> > messages get logged, then you could go many multiples of 10s without
>> > triggering a wake up due to crossing an 8 KB boundary.

Thanks a lot for the in-depth information.
Is the 8KB boundary configureable at compile time?

> /* if we have already flushed that far, consider async commit records */
>
> For this purpose, async commit could mean either commits down with
> synchronous_commit=off, or commits of transactions which touched only
> unlogged tables. So it writes the same 8kb block as last time (but with new
> data at the logical end of the block) and flushes it.

Ah, that explains why my experiments using unlogged tables also
weren't sucessful in avoiding the frequent writes.

Regards, Clemens