Обсуждение: Unix domain instead of TCP socket connections with JDBC.

Using the org.postgresql.Driver JDBC driver is it possible to connect
to Postgres using a unix domain socket instead of a TCP socket (so you
don't have to start the postmaster with -i)? Using a TCP socket
instead of a unix socket seems to slow down requests that return large
result sets by a factor of 3 on the same machine. What's the point of
all the extra CPU overhead if you're on the same machine? A
high-volume server can really do without the extra overhead. Also, for
security reasons it would be slightly nicer to run Postgres without -i
just so there's one less port popping up when you port-scan.

froggle2003@yahoo.com (Alex Martinoff) writes:
> ...  Using a TCP socket
> instead of a unix socket seems to slow down requests that return large
> result sets by a factor of 3 on the same machine.

Seems like a kernel bug to me.  All modern TCP stacks have shortcuts for
local connections.  What platform are you on exactly?

(BTW, this is not an argument against having JDBC support unix-socket
connections; I can see security reasons for that.  But there should not
be performance reasons for it.)

            regards, tom lane

On 7 Sep 2003, Alex Martinoff wrote:

> Using the org.postgresql.Driver JDBC driver is it possible to connect
> to Postgres using a unix domain socket instead of a TCP socket (so you
> don't have to start the postmaster with -i)? Using a TCP socket
> instead of a unix socket seems to slow down requests that return large
> result sets by a factor of 3 on the same machine. What's the point of
> all the extra CPU overhead if you're on the same machine? A
> high-volume server can really do without the extra overhead. Also, for
> security reasons it would be slightly nicer to run Postgres without -i
> just so there's one less port popping up when you port-scan.

Java does not provide an API for dealing with unix sockets.  It might
be possible to create such an interface via JNI, but I doubt you'll get
a whole lot of interest from the JDBC driver developers as the postgresql
JDBC driver is a Type IV (pure java) driver.

Is this factor of 3 difference in time the difference from running psql
over unix sockets vs tcp, or is it the difference between a Java client
and psql?  If it's the latter you're not really doing an apples to apples
comparison.

Kris Jurka

The tomcat developers were working on a hybrid system, that would use
unix sockets via JNI for local connections, but I'm not sure what
happened to it.  Or maybe they used a named pipe instead?  I really
don't know.