Re: Connections hang indefinitely while taking a gin index's LWLockbuffer_content lock(PG10.7)

> 29 сент. 2019 г., в 21:27, Alexander Korotkov <a.korotkov@postgrespro.ru> написал(а):
>
> Patch with fix is attached.  Idea is simple: ginScanToDelete() now
> keeps exclusive lock on left page eliminating the need to relock it.
> So, we preserve left-to-right locking order and can't deadlock with
> ginStepRight().

In this function ginDeletePage(gvs, blkno, BufferGetBlockNumber(me->leftBuffer),...)
we are going to reread buffer
lBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, leftBlkno,
                                 RBM_NORMAL, gvs->strategy);
Is it OK?


> 30 сент. 2019 г., в 0:52, Peter Geoghegan <pg@bowt.ie> написал(а):
>
> Why is it okay
> that there is no nbtree-style distinction between page deletion and
> page recycling?
As far as I understand deleted page is stamped with
GinPageSetDeleteXid(page, ReadNewTransactionId());
It will not be recycled until that Xid is far behind.
BTW we found a small bug (wraparound) in similar GiST and B-tree implementations.
Probably, it's there in GIN too.

--
Andrey Borodin
Open source RDBMS development team leader
Yandex.Cloud