Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> 1. in VACUUM or brin_summarize_new_values, we only process fully loaded
> ranges, and ignore the partial range at end of table.
OK.
> 2. when summarization is requested on the partial range at the end of a
> table, we acquire extension lock on the rel, then compute relation size
> and run summarization with the lock held. This guarantees that we don't
> miss any pages. This is bad for concurrency though, so it's only done
> in that specific scenario.
Hm, I wonder how this will play with the active proposals around
reimplementing relation extension locks. All that work seems to be
assuming that the extension lock is only held for a short time and
nothing much beyond physical extension is done while holding it.
I'm afraid that you may be introducing a risk of e.g. deadlocks
if you do this.
If VACUUM and brin_summarize_new_values both ignore the partial
range, then what else would request this? Can't we just decree
that we don't summarize the partial range, period?
regards, tom lane
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