Re: PATCH: add pg_current_xlog_flush_location function

On 01/11/2016 06:30 AM, Michael Paquier wrote:
>
> Updating LogwrtResult directly when calling your new function
> GetXLogFlushRecPtr() does not strike me as a particularly good idea
> per this portion in XLogFlush():
>
> /* Quick exit if already known flushed */
> if (record <= LogwrtResult.Flush)
> return;
>
> The same counts for GetXLogWriteRecPtr, we had better allocate the
> value in an independent variable as there are checks using it. For
> now it does not matter much for the write position because all the
> code paths doing the checks explicitly update again the pointer
> before looking at it but it seems to me that using an independent
> variable would make the code more robust.

Why? LogwrtResult only serves as a local cache of shared values, so
there should be no danger of skipping something.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services