Re: [HACKERS] strange behavior of UPDATE

Tom Lane wrote:
>
> Edmund Mergl <E(dot)Mergl(at)bawue(dot)de> writes:
> > Some more numbers:
>
> > database #rows inserts create make_sqs make_nqs
> > index selects updates
> > ----------------------------------------------------------------------------
> > pgsql 10.000 00:24 00:09 00:16 00:25
> > pgsql 100.000 04:01 01:29 01:06 49:45
> > pgsql 1.000.000 39:24 20:49 23:42 ???
>
> > whereas the increase of elapsed time is somewhat proportional
> > to the number of rows, for the update-case it is rather
> > exponential.
>
> Those are attention-getting numbers, all right. I think that the two
> equal-key problems I found last night might partially explain them;
> I suspect there are more that I have not found, too. I will look into
> it some more.
>
> Could you try the same queries with no indexes in place, and see what
> the time scaling is like then? That would confirm or deny the theory
> that it's an index-update problem.

here they are, and yes, I double-checked them twice !

database #rows inserts create make_sqs make_nqs
index selects updates
----------------------------------------------------------------------------
pgsql 10.000 00:24 - 00:13 00:05
pgsql 100.000 04:01 - 00:83 00:32
pgsql 1.000.000 39:24 - 26:36 26:52

>
> Question for the hackers list: are we prepared to install purely
> performance-related bug fixes at this late stage of the 6.5 beta cycle?
> Bad as the above numbers are, I hesitate to twiddle the btree code and
> risk breaking things with only a week of testing time to go...
>
> regards, tom lane

if there is anything else I can do, just let me know.

Edmund

--
Edmund Mergl mailto:E(dot)Mergl(at)bawue(dot)de
Im Haldenhau 9 http://www.bawue.de/~mergl
70565 Stuttgart fon: +49 711 747503
Germany