Re: [HACKERS] strange behavior of UPDATE

Tom Lane wrote:
> 
> Edmund Mergl <E.Mergl@bawue.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.Mergl@bawue.de
Im Haldenhau 9        http://www.bawue.de/~mergl
70565 Stuttgart       fon: +49 711 747503
Germany