Re: Speedup twophase transactions

Thanks, Kevin.

> I assume that last one should have been *Patched master with 2PC”?

Yes, this list should look like this:

Current master without 2PC: ~42 ktps
Current master with 2PC: ~22 ktps
Patched master with 2PC: ~36 ktps

And created CommitFest entry for this patch.

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


> On 10 Dec 2015, at 00:37, Kevin Grittner <kgrittn@gmail.com> wrote:
> 
> On Wed, Dec 9, 2015 at 12:44 PM, Stas Kelvich <s.kelvich@postgrespro.ru> wrote:
> 
>> Now 2PC in postgres does following:
>> * on prepare 2pc data (subxacts, commitrels, abortrels, invalmsgs) saved to xlog and to file, but file not is not fsynced
>> * on commit backend reads data from file
>> * if checkpoint occurs before commit, then files are fsynced during checkpoint
>> * if case of crash replay will move data from xlog to files
>> 
>> In this patch I’ve changed this procedures to following:
>> * on prepare backend writes data only to xlog and store pointer to the start of the xlog record
>> * if commit occurs before checkpoint then backend reads data from xlog by this pointer
>> * on checkpoint 2pc data copied to files and fsynced
>> * if commit happens after checkpoint then backend reads files
>> * in case of crash replay will move data from xlog to files (as it was before patch)
> 
> That sounds like a very good plan to me.
> 
>> Now results of benchmark are following (dual 6-core xeon server):
>> 
>> Current master without 2PC: ~42 ktps
>> Current master with 2PC: ~22 ktps
>> Current master with 2PC: ~36 ktps
> 
> I assume that last one should have been *Patched master with 2PC"?
> 
> Please add this to the January CommitFest.
> 
> --
> Kevin Grittner
> EDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company