Ken Bowen wrote:
Hi all (especially Chris -- very informative long post today on
Tomcat/MySQL):
For a several reasons (including the apparent infinite default for
connection timeout), I'm contemplating switching one or two projects
from MySQL to PostgreSQL. I'd like to gather opinions on the tradeoffs,
including:
Unfortunately, MySQL isn't really that tunable. On the other hand, MySQL
requires very little in the way of tuning!
Not true, unless your needs are very modest. The InnoDB engine has a
large number of tunable parameters - however, they are poorly and
incompletely documented in the MySQL manual, while changing them may
cause your indexes to be silently dropped when you restart MySQL. The
MyISAM engine also has a number of tunable parameters, but I would only
use this engine in preference to InnoDB if you need full text indexing,
and only for the specific tables that require full text indexes.
I created a couple of proof-of-concept projects with PostgreSQL for
someone about six months ago, and the only really puzzling thing what
how to set up "sequences" corresponding to MySQL's AUTOINCREMENT (I'm
not sure I've really wrapped head around it completely anyway). For
those small projects, it worked well, but there was no stress involved.
Where you would use an AUTO_INCREMENT column in MySQL, use a SERIAL
column in PostgreSQL which creates a sequence for you. There's a good
description in the PostgreSQL manual:
http://www.postgresql.org/docs/8.3/static/datatype-numeric.html#DATATYPE-SERIAL
I'd like to hear about people's experiences and what they think are the
strengths and weaknesses of each DBMS for use behind Tomcat.
PostgreSQL is not perfect, but it has proven to be faster and far more
reliable than MySQL in the projects where I have tested both. The full
text indexing in PostgreSQL is far more sophisticated, although at the
cost of slightly more complexity to use. Tuning is generally
straightforward, and far less of a black art than it is with MySQL.
Finally, I spend far less time analysing query plans and optimising by
hand when using PostgreSQL rather than MySQL, as the former handles
joins across more than one table far better.
Thanks much in advance,
Ken Bowen
Chris
--
Chris Wareham
Senior Software Engineer
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