Re: comunication protocol - Mailing list pgsql-hackers

On 8/8/07, Omar Bettin <o.bettin@tiscali.it> wrote:
>
>
> Hi,
> I have installed postgresql to my client as a server for a progam
> (libpq.dll/VCL based) that I wrote for them.
>
> Every is working fine, but I noted some general slowness,  compared with an
> older database system (iAnywhere ADS)
> due (I think) to the  text based communication protocol.

you should maybe report a couple of specific things (explain analyze,
etc) for analysis and make sure your expectations are reasonable.  It
is possible simple configuration issues or query changes might be the
answer here, then again, maybe not.

> I know there is the possibility to adopt a ssl compressed connection but I
> think a pure compressed connections could be better.

I think you are looking in the wrong direction here.

> So, I have studied the postgresql sources and I have tried to implement some
> compression between the backend and the frontend,
> using pglz_compress/pglz_decompress on be-secure.c and fe-secure.c.
>
> At the moment is working good on a local configuration, got some problems on
> a remote connection due I think a different way to communicate.

AFAIK, the fastest possible way to get data off the server, skipping
all data and text processing is to write a SPI routine, and stream the
data out locally to the server.   I am doing exactly this in a
particular problem that requires high performance and I can tell you
that SPI is fast.

http://developer.postgresql.org/pgdocs/postgres/spi-examples.html

That way you will bypass the protocol completely.  On my computer, I
get roughly 300k records/sec raw read performance using libpq and
about 1.3m records sec using a hacked SPI and streaming to disk.  This
may not be helpful for your application but if you are exploring ways
to bypass protocol overhead this is where I would start.

By the way, your problem might be the VCL driver you are using to
access the database.  The highest performance driver I have used
(which wraps libpq) is the Zeos library which is very fast.

> There are other ways (other than be-secure and fe-secure) with which the
> backend comunicate with the frontend?
> And, do you think this solution could speed up something?

Once again, I would start by looking at your application and posting
here to make sure you are looking at the right bottlenecks (you
_suspect_ the protocol is the problem, but is it really?).

this means:
* explain analyze/queries (w/how fast you think it should be going)
* relevant .conf settings
* time measurements from the app

merlin