Re: VACUUM ANALYZE blocking both reads and writes to a table

Actually, while on the topic:

> date: 2007-09-10 13:58:50 -0400; author: alvherre; state: Exp; lines: +6 -2;
> Remove the vacuum_delay_point call in count_nondeletable_pages, because we hold
> an exclusive lock on the table at this point, which we want to release as soon
> as possible. This is called in the phase of lazy vacuum where we truncate the
> empty pages at the end of the table.

Even with the fix the lock is held. Is the operation expected to be
"fast" (for some definition of "fast") and in-memory, or is this
something that causes significant disk I/O and/or scales badly with
table size or similar?

I.e., is this enough that, even without the .4 bug, one should not
really consider VACUUM ANALYZE non-blocking with respect to other
transactions?

(I realize various exclusive locks are taken for short periods of time
even for things that are officially declared non-blocking; the
question is whether this falls into this category.)

--
/ Peter Schuller

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