On Tue, Oct 28, 2014 at 9:25 PM, Simon Riggs <si...@2ndquadrant.com> wrote:
> On 13 October 2014 10:05, Petr Jelinek <p...@2ndquadrant.com> wrote: > > >> I worked bit on this patch to make it closer to committable state. > > > Here is updated version that works with current HEAD for the October > > committfest. > > I've reviewed this and it looks good to me. Clean, follows existing > code neatly, documented and tested. > > Please could you document a few things > > * ExtendCommitTS() works only because commit_ts_enabled can only be > set at server start. > We need that documented so somebody doesn't make it more easily > enabled and break something. > (Could we make it enabled at next checkpoint or similar?) > > * The SLRU tracks timestamps of both xids and subxids. We need to > document that it does this because Subtrans SLRU is not persistent. If > we made Subtrans persistent we might need to store only the top level > xid's commitTS, but that's very useful for typical use cases and > wouldn't save much time at commit. > Hm. What is the performance impact of this feature using the latest version of this patch? I imagine that the penalty of the additional operations this feature introduces is not zero, particularly for loads with lots of short transactions. -- Michael
