On Wed, Jun 15, 2016 at 6:26 PM, Robert Haas <robertmhaas@gmail.com> wrote: > > On Wed, Jun 15, 2016 at 2:41 AM, Thomas Munro > <thomas.munro@enterprisedb.com> wrote: > > I spent some time chasing down the exact circumstances. I suspect > > that there may be an interlocking problem in heap_update. Using the > > line numbers from cae1c788 [1], I see the following interaction > > between the VACUUM, UPDATE and SELECT (pg_check_visible) backends, all > > in reference to the same block number: > > > > [VACUUM] sets all visible bit > > > > [UPDATE] heapam.c:3931 HeapTupleHeaderSetXmax(oldtup.t_data, xmax_old_tuple); > > [UPDATE] heapam.c:3938 LockBuffer(buffer, BUFFER_LOCK_UNLOCK); > > > > [SELECT] LockBuffer(buffer, BUFFER_LOCK_SHARE); > > [SELECT] observes VM_ALL_VISIBLE as true > > [SELECT] observes tuple in HEAPTUPLE_DELETE_IN_PROGRESS state > > [SELECT] barfs > > > > [UPDATE] heapam.c:4116 visibilitymap_clear(...) > > Yikes: heap_update() sets the tuple's XMAX, CMAX, infomask, infomask2, > and CTID without logging anything or clearing the all-visible flag and > then releases the lock on the heap page to go do some more work that > might even ERROR out.
>
Can't we clear the all-visible flag before releasing the lock? We can use logic of already_marked as it is currently used in code to clear it just once.
