"Ron Peacetree" <rjpeace@earthlink.net> writes:
> "Tom Lane" <tgl@sss.pgh.pa.us> wrote in message
> news:4096.1049860699@sss.pgh.pa.us...
>> Ron, the tests that I've seen offer no support for that thesis.
> What tests? I've seen no tests doing head-to-head,
> feature-for-feature comparisons (particularly for low level features
> like locking) of PostgreSQL vs the "biggies": DB2, Oracle, and SQL
> Server. What data I have been able to find is application level, and
> certainly not head-to-head.
Who said anything about feature-for-feature comparisons? You made an
(unsupported) assertion about performance, which has little to do with
feature checklists.
The reason I don't believe there's any fundamental MVCC problem is that
no such problem showed up in the head-to-head performance tests that
Great Bridge did about two years ago. GB is now defunct, and I have
not heard of anyone else willing to stick their neck out far enough to
publish comparative benchmarks against Oracle. But I still trust the
results they got.
I have helped various people privately with Oracle-to-PG migration
performance problems, and so far the issues have never been MVCC or
transaction issues at all. What I've seen is mostly planner
shortcomings, such as failure to optimize "foo IN (sub-SELECT)"
decently. Some of these things are already addressed in development
sources for 7.4.
>> Postgres certainly has plenty of performance issues, but I have no
>> reason to believe that the fundamental MVCC mechanism is one of
>> them.
> Where in your opinion are they then? How bad are they in comparison
> to MySQL or any of the "Big Three"?
See the TODO list for some of the known problems. As for "how bad are
they", that depends completely on the particular application and queries
you are looking at ...
regards, tom lane
