On Fri, Aug 5, 2016 at 11:26 PM, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Aug 5, 2016 at 02:43:37PM -0300, Claudio Freire wrote: > But doing the WARM chain backtracking and checking for previous > versions with appropriate keys should be enough to support this use > case too, it just needs to be well optimized to avoid seriously > impacting performance on the average case.
Yes, that was an idea I had to --- if the in-page HOT chain already has the key, we know it is already in the index and we can skip the index addition.
I just don't know how would you do that without delaying/not-doing HOT chain prune. As soon as root and intermediate HOT tuples are gone, all information is lost. You may delay that, but that will defeat the whole purpose. If chains are not pruned in-time, you may not find any free space in the page and end up doing a cold update anyways. But may be I am missing something and Claudio has a different idea.