Andres Freund wrote: > While looking at the multixact truncation code (mail nearby), I've > noticed that there's a significant difference in the way multixact > members are accessed since fkey locks were introduced: > > <9.3 when heap_lock_tuple finds a XMAX_IS_MULTI tuple it executes > MultiXactIdWait() which in turn uses GetMultiXactIdMembers() to get the > xids to wait for. But it skips the lookup if the mxid we lookup is older > than OldestVisibleMXactId. > > 9.3+ instead always looks up the members because GetMultiXactIdMembers() > is also used in cases where we need to access old xids (to check whether > members have commited in non-key updates).
But HeapTupleSatisfiesUpdate(), called at the top of heap_lock_tuple, has already called MultiXactIdIsRunning() (which calls GetMembers) before that's even considered. So the call heap_lock_tuple should have members obtained from the multixact.c cache. Am I misunderstanding which code path you mean? -- Álvaro Herrera http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
