On 07/03/2017 06:30 PM, Chapman Flack wrote:
On 07/03/2017 09:39 AM, Heikki Linnakangas wrote:
Hmm. That's not the problem, though. Imagine that instead of the loop
above, you do just:
WALInsertLockUpdateInsertingAt(CurrPos);
AdvanceXLInsertBuffer(EndPos, false);
AdvanceXLInsertBuffer() will call XLogWrite(), to flush out any pages
before EndPos, to make room in the wal_buffers for the new pages. Before
doing that, it will call WaitXLogInsertionsToFinish()
Although it's moot in the straightforward approach of re-zeroing in
the loop, it would still help my understanding of the system to know
if there is some subtlety that would have broken what I proposed
earlier, which was an extra flag to AdvanceXLInsertBuffer() that
would tell it not only to skip initializing headers, but also to
skip the WaitXLogInsertionsToFinish() check ... because I have
the entire region reserved and I hold all the writer slots
at that moment, it seems safe to assure AdvanceXLInsertBuffer()
that there are no outstanding writes to wait for.
Yeah, I suppose that would work, too.
- Heikki
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