I've install PostgreSQL , but it seem to be slow with the default configuration . I read in the document and find out some interesting parameters :

But changing it with out any knowleage is not the right way . I need some tip for that , could you please help me ?
Other thing is how to test the perfomance of postgres ( the number of transaction per second ), I want to see how effect it was when I changed some parameter

Please help me

How is it that you're getting the feeling of it being slow? You're running a query that seems to take longer than it should? Over how much data? How many people access the database? Are you using indexes? You need to know what is going slow before you can fix it For instance, changing the vacuum_mem only improves the maintenance of the database, not it's operation.

If a particular query is running slow, you can use EXPLAIN to show what's happening for that query.

As for benchmarking... that's harder depending on what's going on. For instance, if you're the only user of the database, it's going to spend most of its time waiting for you to do something, so transactions per second is not going to be a useful figure. You could write up a script for psql that performs 1000 inserts and use 'time' to see how long it takes. Also test 1000 queries, updates, and deletes for a better picture.

I think that is one of the main problem to improve speed . But I can not find out where to turn it on . In creatdb does not contain it .

Yes , you're right , I just image in my mind because I have no experience . But I want my database system can do as much as transaction per second as posible . For the maximum of people log in , I think it not so importance ( 50 is too good ) .
Now for example I set 50 is the maximum of connection , and how to make the number of transation boot up . Can you give me something more ?

Indexes are specific to your data. For example, if you have a table called "customers", and you regularly do a query like
select * from customers where name like 'A%'
then your query would be sped up a lot by creating an index on the name field, which you would do via an SQL command like "CREATE INDEX custname ON customer (name)"

I understand you want maximum performance, but that can only be achieved on a per-system basis. You can tune other things separately, like your hard drive performance, and that will very likely improve postgres as a side effect, but to try and measure transactions per second makes almost no sense. Inserting a row into a 40 column table will take longer than inserting a row into a 2 column table, but they are both transactions. A query that retrieves data from fifteen different tables with lots of crazy joins is a single transaction too, but will probably take far longer than the two inserts. You need to set up your system and create tests for the activities that will apply to your system - there is no single 'golden configuration' that just makes Postgres a speed demon.

This url http://www.phpbuilder.com/columns/sm...21.php3?page=2 helps explain the shared memory settings you listed above. The fsync parameter improves speed at the possible expense of data integrity (if the system crashes or loses power, your database may be in an inconsistent state - whether this is important to you or not depends on how much your database is used and how important the data is).