Thread: comunication protocol
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.
I know there is the possibility to adopt a ssl compressed connection but I think a pure compressed connections could be better.
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.
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?
For the moment I have big troubles to debug the server, have you some informations how to debug it with MinGW?
Thanks and sorry form my english!
Omar Bettin
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
Em Quarta 08 Agosto 2007 12:02, Omar Bettin escreveu: > Hi, > I have installed postgresql to my client as a server for a progam > (libpq.dll/VCL based) that I wrote for them. Borland VCL? What component are you using? Gustavo.
Merlin Moncure wrote: > 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 think this is not necessary because I have used the same application with two different servers and you can see the speed differences just using it. > >> 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. > Interesting,do you thing that is possible to implement some send() in the interface? > 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. > > I have tried ZeosLib and for me is unusable (too slow), I use a strong modified PostgresDAC. >> 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 > > I just switch form Application1 (IAnywhere Ads) to Application2 (Postgresql) optimizing the VCL (strong modifications to PostgresDAC sources) and sow the results. My application needs to full open some tables and with this protocol is like to download a long text file. omar
Gustavo Tonini wrote: > Em Quarta 08 Agosto 2007 12:02, Omar Bettin escreveu: > >> Hi, >> I have installed postgresql to my client as a server for a progam >> (libpq.dll/VCL based) that I wrote for them. >> > > Borland VCL? What component are you using? > > Gustavo. > I use a strong modified PostgresDAC component. Omar
On 8/9/07, Omar Bettin <o.bettin@tiscali.it> wrote: > Merlin Moncure wrote: > > 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. > > > Interesting,do you thing that is possible to implement some send() > in the interface? SPI is an interface which allows you to make sql calls from C code (PostgreSQL allows you to link C code compiled as a .so to the server and call -- see numerous examples in contrib). The routine you need to exploit is SPI_getbinval which gives you Datum (essentially a variant) pointing to the internal binary representation of your field.In theory you could collect the data into a bufferand send() it off although thats a lot of work IMO. Also, I would only advise this for fast dumps from a single table (no joins, etc). > I have tried ZeosLib and for me is unusable (too slow), I use a > strong modified PostgresDAC. I'm suprised -- I know the ZeosLib internals and it's a very thin layer over libpq. Here is what I suggest: * turn on statement logging in the server (set log_min_duration_statement) * make some operations in the app which you suggest are slow -- they will show up in the log * 'explain analyze' the query from the psql console make note of the times and post back (maybe move this thread to the -performance list) merlin
Merlin Moncure wrote: > On 8/9/07, Omar Bettin <o.bettin@tiscali.it> wrote: > >> Merlin Moncure wrote: >> >>> 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. >>> >>> >> Interesting,do you thing that is possible to implement some send() >> in the interface? >> > > SPI is an interface which allows you to make sql calls from C code > (PostgreSQL allows you to link C code compiled as a .so to the server > and call -- see numerous examples in contrib). The routine you need > to exploit is SPI_getbinval which gives you Datum (essentially a > variant) pointing to the internal binary representation of your field. > In theory you could collect the data into a buffer and send() it off > although thats a lot of work IMO. Also, I would only advise this for > fast dumps from a single table (no joins, etc). > why not joins? > >> I have tried ZeosLib and for me is unusable (too slow), I use a >> strong modified PostgresDAC. >> > > I'm suprised -- I know the ZeosLib internals and it's a very thin > layer over libpq. Here is what I suggest: > > * turn on statement logging in the server (set log_min_duration_statement) > * make some operations in the app which you suggest are slow -- they > will show up in the log > * 'explain analyze' the query from the psql console > > make note of the times and post back (maybe move this thread to the > -performance list) > > merlin > > So, you aren't agree with the compression... I have sow the network statistics and in some cases, the network traffic is very big. Probably a better setup could increase the performance by a few points percent but I think a compressed protocol could increase the communication by 2/3 times. I think the biggest bottleneck in the whole system is just that. :..try to get a query from a remote server with a 56k modem! :) Omar > ---------------------------(end of broadcast)--------------------------- > TIP 4: Have you searched our list archives? > > http://archives.postgresql.org > >
Ühel kenal päeval, N, 2007-08-09 kell 17:12, kirjutas Omar Bettin: > > So, you aren't agree with the compression... > > I have sow the network statistics and in some cases, the network traffic > is very big. > Probably a better setup could increase the performance by a few points > percent but > I think a compressed protocol could increase the communication by 2/3 times. > > I think the biggest bottleneck in the whole system is just that. > > :..try to get a query from a remote server with a 56k modem! :) Why not just set up an ssh2 tunnel with both encryption and compression and access your remote db over that ? ---------- Hannu
Hannu Krosing wrote: > Ühel kenal päeval, N, 2007-08-09 kell 17:12, kirjutas Omar Bettin: > > > > Why not just set up an ssh2 tunnel with both encryption and compression > and access your remote db over that ? > > I know that possibility, but I'm just thinking probably an "ad hoc" protocol for applications that needs to locate, range, skip, lookup, bookmark etc... a lot of records, could increase the system performance. By that, I don't want to discuss about PostgreSQL performance by itself but about a to much "generalist" protocol. With libpq, after you got the result, you have to implement locally some find, range etc, routines and on the other side there is a DBMS born to do that! My application need both type of connection LAN/WAN and here (in Italy) still some lack of wide-band infrastructure. Also installing certificates on a LAN contest is a bit a "dirty" way to solve the problem. Omar