| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru> |
| Subject: | Re: Making all nbtree entries unique by having heap TIDs participate in comparisons |
| Date: | 2018-11-04 04:26:21 |
| Message-ID: | CAH2-Wz=gtkPxd28QDJukv16vcEhkHqRcvhTPz69R44WJFh=PTA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Nov 2, 2018 at 5:00 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> I had the opportunity to discuss this patch at length with Heikki
> during pgConf.EU.
> The DESC heap TID sort order thing probably needs to go. I'll probably
> have to go fix the regression test failures that occur when ASC heap
> TID order is used.
I've found that TPC-C testing with ASC heap TID order fixes the
regression that I've been concerned about these past few weeks. Making
this change leaves the patch a little bit faster than the master
branch for TPC-C, while still leaving TPC-C indexes about as small as
they were with v6 of the patch (i.e. much smaller). I now get about a
1% improvement in transaction throughput, an improvement that seems
fairly consistent. It seems likely that the next revision of the patch
series will be an unambiguous across the board win for performance. I
think that I come out ahead with ASC heap TID order because that has
the effect of reducing the volume of WAL generated by page splits.
Page splits are already optimized for splitting right, not left.
I should thank Heikki for pointing me in the right direction here.
--
Peter Geoghegan
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