Tom Lane wrote:
<robin.c.smith@xxxxxx> writes:
I have been testing the performance of PostgreSQL using the simple tool
found at http://benchw.sourceforge.net however I have found that all the
queries it run execute with sequential scans. The website where the code
runs has examples of the execution plan using indexes.
The reason the website gets indexscans is that he's fooled with the
planner cost parameters. In particular I see that...(snipped)
Indeed I did - probably should have discussed that alteration better in
the documentation for the test suite!
In addition I was a bit naughty in running the benchmark using size 1
(i.e about 1G) an a box with 2G ram - as this meant that (on the machine
I was using then anyway) indexscans on query 0 and 1 were *always*
better than the sequential options.
A better test is to use the size factor at 2 x physical ram, as then the
planners defaults make more sense! (unless or course you *want* to model
a data mart smaller than physical ram).
Best wishes
Mark
