Re: Speedup twophase transactions

Thanks a lot for your edits, now that patch is much more cleaner.

> Your comments say
> 
>   "In case of crash replay will move data from xlog to files, if that hasn't happened before."
> 
> but I don't see that in code. Can you show me where that happens? 

xact.c calls RecreateTwoPhaseFile in xact_redo() function (xact.c:5596)

> On 09 Jan 2016, at 18:29, Simon Riggs  wrote:
> 
> Hmm, I was just preparing this for commit.
> 
> Please have a look at my mild edits and extended comments. 


One concern that come into my mind while reading updated
patch is about creating extra bool field in GlobalTransactionData structure. While this improves readability, it
also increases size of that structure and that size have impact on performance on systems with many cores
(say like 60-80). Probably one byte will not make measurable difference, but I think it is good idea to keep
GXact as small as possible. As far as I understand the same logic was behind split of 
PGPROC to PGPROC+PGXACT in 9.2 (comment in proc.h:166)

Stas Kelvich
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company