Alvaro Herrera wrote:
> > BTW, shouldn't there be a step in BRIN vacuum that scans all the BRIN pages?
> > If an empty page is missing from the FSM for any reason, there's nothing to
> > add it there.
>
> Probably. I didn't change this part yet. There are two things to fix:
> 1. since we use log_newpage_buffer(), we log the initialization but not
> the recording into FSM, so the page would be forgotten about. This can
> be tested with PageIsEmpty(). An alternative to the vacuum scan is to
> use our own WAL record that not only logs the initialization itself but
> also the FSM update. Not sure this is worth the trouble.
>
> 2. additionally, if brin_getinsertbuffer extends the relation but we
> crash before the caller initializes it, the page would be detected by
> PageIsNew instead and would also need initialization.
Added this part. It's using log_newpage_buffer too. The vacuum scan
fixes the whole FSM, though, so after vacuum the FSM is up to date.
I think we could shave off a few bytes by using a separate WAL record,
but I'm not sure it's worth the trouble.
I intend to push this tomorrow.
I now think the free space calculations are broken, but I'll leave that
for later.
--
Álvaro Herrera http://www.2ndQuadrant.com/
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