From: | Andres Freund <andres(at)anarazel(dot)de> |
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To: | pgsql-hackers(at)postgresql(dot)org |
Subject: | pageinspect option to forgo buffer locking? |
Date: | 2017-11-09 17:49:11 |
Message-ID: | 20171109174911.m6nfe3gmb3ugk53x@alap3.anarazel.de |
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Lists: | pgsql-hackers |
Hi,
Occasionally, when debugging issues, I find it quite useful to be able
to do a heap_page_items() on a page that's actually locked exclusively
concurrently. E.g. investigating the recent multixact vacuuming issues,
it was very useful to attach a debugger to one backend to step through
freezing, and display the page in another session.
Currently the locking in get_raw_page_internal() prevents that. If it's
an option defaulting to off, I don't see why we couldn't allow that to
skip locking the page's contents. Obviously you can get corrupted
contents that way, but we already allow to pass arbitrary stuff to
heap_page_items(). Since pinning wouldn't be changed, there's no danger
of the page being moved out from under us.
Greetings,
Andres Freund
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