Re: Why are we waiting?

Simon Riggs <simon@2ndquadrant.com> writes:
> There were only 2 lock delays for FirstLockMgrLock in SHARED mode, so it
> seems believable that there were 0 lock delays in EXCLUSIVE mode.

Not really, considering the extremely limited use of LW_SHARED in lock.c
(GetLockConflicts is used only by CREATE INDEX CONCURRENTLY, and
GetLockStatusData only by the pg_locks view).  For the type of benchmark
that I gather this is, there should be *zero* LW_SHARED acquisitions at
all.  And even if there are some, they could only be blocking against
the (undoubtedly much more frequent) LW_EXCLUSIVE acquisitions; it's not
very credible that there is zero contention among the LW_EXCLUSIVE locks
yet a few shared acquirers manage to get burnt.
        regards, tom lane