Tom Lane schrieb:
ITAGAKI Takahiro <[EMAIL PROTECTED]> writes:
Here is a patch to log conflicted queries on deadlocks. Queries are dumped
at CONTEXT in the same sorting order as DETAIL messages. Those queries are
picked from pg_stat_get_backend_activity, as same as pg_stat_activity,
so that users cannot see other user's queries.
Applied with revisions. It's a cute idea --- I first thought it
couldn't work reliably because of race conditions, but actually we
haven't aborted our own transaction at this point, so everyone else
involved in the deadlock is still waiting and it should be safe to
grab their activity strings.
However there was still a big implementation problem, which is that
looking at pg_stat_activity could deliver very stale results, not only
about other backends' queries but even our own. The data for that
comes from a snapshot that might have been taken much earlier in our
transaction. I replaced the code you were using with a new pgstat.c
entry point that delivers up-to-date info directly from the shared
memory array.
Is there a chance that I might get this patch running in 8.1 and 8.2
releases? I modified the original patch to compile with 8.2.7, but it
did not work:
ERROR: deadlock detected
DETAIL: Process 26289 waits for ShareLock on transaction 57039190;
blocked by process 26277.
Process 26277 waits for ShareLock on transaction 57039191; blocked by
process 26289.
CONTEXT: Process 26289: <backend information not available>
Process 26277: <backend information not available>
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