Performance of jdbc insert statements and select nextval

i found the following problem:

Summary:
10000 inserts with pgadmin tool into one table (primary key bigserial) can
be done wihtin 3 seconds. If i perform the same job with jdbc this takes
13 seconds. The insert statement is prepared only once, the statement for
fetching the nextval also. If i omit the select nextval execution time
improves to 8 seconds. Can anybody tell me why jdbc is 3 to four times
slower than pgadmin? I am using Postgresql 8.2 and 8.3 Database server,
java 1.5 and 1.6 and i tried the drivers 8.2 and 8.3 in type 3 and type 4.
The execution times are always identical.

Precise description:
The problem results from the following application problem. We are
developing a web application with geronimo application server, JPA
persistence technology and PostgreSQL database server. The application is
tested on Ubuntu Linux and Windows XP, with postgresql 8.2 and 8.3 servers
on java 1.5 and 1.6 platform. I made a test with "logical" insert of
objects which results in 50000 inserts can be done within 2 minutes, what
means 416 inserts per second, or 1 insert in 2/1000 sec (2ms). The cost
estimate with explain for an insert is on the other hand is 0,4 ms. So,
where is the gap? I left JPA and tried jdbc. Here i found out: 10000
inserts in sql script can be done by PGAdmin within 3 seconds, a simple
jdbc loader program needs 13 seconds. Leaving the id generation to the
database, this can be done within 8 sec (but in my jpa world i of course
need the id, and there was a severe problem of leaving this task to the
jpa model. The automatic id generation (which of course is supported by
jpa) did not work in postgresql if the tables are in a schema).

This is my jdbc test program code:

Yet now i have tried to other database servers. MySql GA and Oracle XE
(10g Express). Both servers lead to the same performance (10000 inserts
within 13 seconds). So, PostgreSQL is not less or more performant than
others. Following a hint from Graig Ringer. May it be that a firewall or
virus scanner forces the performance slow down? This perhaps might explain
why the system does not scale with faster hardware.

Thanks, Ralf
BGS Beratungsgesellschaft
Software Systemplanung AG




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