On 12 January 2016 at 05:58, Michael Paquier <michael.paqu...@gmail.com> wrote:
> On Tue, Jan 12, 2016 at 6:35 AM, Simon Riggs wrote: > > Comments in xlog.c say > > > > "In addition to the shared variable, each backend has a private copy of > > LogwrtResult, which is updated when convenient." > > It is therefore valid to update the value of both Write and Flush > positions > > at the same time, any time either is required. > > Yes I saw this one yesterday when looking at this code. My comment > regarded the potential interactions between this field with XLogFlush, > but now I see that my concerns are not valid, updating more frequently > LogwrtResult may save some cycles though. > > > My suggested commit pattern for this is... > > 1. Update existing function to maintain LogwrtResult more eagerly > (separate > > patch) > > The only place I see now that would benefit a bit from that is > UpdateMinRecoveryPoint when info_lck is taken, which can be called by > XLogFlush. Though I would expect this to have minimal impact. > > > 2. Have the patch use the existing function name (main patch) > > Yeah, we had better just use GetFlushRecPtr and be done with it. It > seems that there is little point to add a new function, and it is not > going to be called that much so its effects in updating LogwrtResult > would be minimized for a single backend. > Patch committed, thanks for patch and review. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
