On Tue, Mar 20, 2012 at 12:34 PM, Atri Sharma <atri.j...@gmail.com> wrote: > > > -----Original Message----- > From: Merlin Moncure [mailto:mmonc...@gmail.com] > Sent: 20 March 2012 22:50 > To: Atri Sharma > Cc: Heikki Linnakangas; Alvaro Herrera; Daniel Farina; Andrew Dunstan; Dave > Page; Pg Hackers > Subject: Re: [HACKERS] Regarding column reordering project for GSoc 2012 > > On Tue, Mar 20, 2012 at 11:57 AM, Atri Sharma <atri.j...@gmail.com> wrote: >> >> >> -----Original Message----- >> From: Merlin Moncure [mailto:mmonc...@gmail.com] >> Sent: 20 March 2012 20:52 >> To: Atri Sharma >> Cc: Heikki Linnakangas; Alvaro Herrera; Daniel Farina; Andrew Dunstan; > Dave >> Page; Pg Hackers >> Subject: Re: [HACKERS] Regarding column reordering project for GSoc 2012 >> >> On Tue, Mar 20, 2012 at 6:58 AM, Atri Sharma <atri.j...@gmail.com> wrote: >>> -----Original Message----- >>> From: Merlin Moncure [mailto:mmonc...@gmail.com] >>> Sent: 20 March 2012 03:15 >>> To: Heikki Linnakangas >>> Cc: Alvaro Herrera; Atri Sharma; Daniel Farina; Andrew Dunstan; Dave > Page; >>> Pg Hackers >>> Subject: Re: [HACKERS] Regarding column reordering project for GSoc 2012 >>> >>> On Mon, Mar 19, 2012 at 2:49 PM, Heikki Linnakangas >>> <heikki.linnakan...@enterprisedb.com> wrote: >>>> On 19.03.2012 21:29, Alvaro Herrera wrote: >>>>> >>>>> >>>>> Excerpts from Atri Sharma's message of lun mar 19 16:20:09 -0300 2012: >>>>> >>>>>> I was just going through PGfoundry and I think I will be able to work >>>>>> on the PL/Java project.Please let me know If I can proceed further on >>>>>> ot for GSOC and also,if currently there is any work that needs to be >>>>>> done on PL/java. >>>>> >>>>> >>>>> Hm, I'm not sure on PL/Java. As far as I know, it is a dead project. >>>> >>>> >>>> I haven't followed PL/java either, but it doesn't look quite dead to me. >>> The >>>> last release was in September 2011, and there are active discussions on >>> the >>>> mailing lists. If it's not completely up-to-date with latest JDK and >>>> PostgreSQL releases, perhaps bringing it up-to-date and then adding some >>>> missing functionality would be a useful GSoC project. >>>> >>>> I would suggest that you ask on the pl/java mailing list if there is >>>> something suitable for a GSoC project there, and if one of the pl/java >>>> developers would be willing to mentor. >>> >>> pl/java works pretty well and is somewhat widely used although it >>> might need some more active maintainers. just jumping into the >>> project and nailing some old bugs and getting the juices flowing would >>> be a tremendous help, as well as the less glamorous work of >>> documentation and regular status updates. >>> >>> one pl/java based project that IMO is just screaming to be done is a >>> pl/java based FDW (wrapping JDBC) that would approximately reproduce >>> dblink...maybe with some extra features geared towards ETL type jobs >>> like a row based callback for transformations in java. >>> >>> Merlin >>> >>> >>> --------------------------- >>> Hi Merlin >>> >>> Thanks for the idea. >>> >>> Could you please elaborate more on the project idea? It would be a great >>> help for me. >> >> sure: >> first start here: http://wiki.postgresql.org/wiki/Foreign_data_wrappers >> and take a look at all the various fdw projects. they all utilize the >> high level interfaces that postgresql provides to incorporate external >> datasources and expose them you can query them as if they were views >> or tables. as you can see, this interface is popular with the >> proliferation of projects to expose this or that. what i'm thinking >> is you make a fdw that invokes pl/java routines that make jdbc calls >> out to external databases. for fetching data and building sets. as >> long as you stick to vanilla jdbc calls, you then have a fdw that can >> gather data from pretty much anything you can access via jdbc url >> which is quite nice. >> >> The fdw API is a C api, so you need to figure out how to proxy to your >> pl/java calls where the real work is done -- I haven't done that so >> I'm not sure if this is even technically feasible. If you can make >> SPI calls from your fdw routines, that's one path through. Tou have >> lots of previous work to crib from though and hopefully there's a path >> through. As far as the ETL stuff I was talking about -- that was just >> me thinking out loud...better to just get the basic mechanics working >> up front.. For now, if you're interested in doing this, start >> thinking about how to marry the fdw interface to pl/java...one you get >> 'hello world' there, it's all about where you want tot take it. >> >> This is an interesting project -- you should entertain no illusions of >> it making it into core, but if done right and completed it will raise >> visibility of both pl/java and postgresql. >> >> Merlin >> >> >> ----------------------- >> Hi Merlin, >> >> First of all,thanks a lot for the extensive reply and explanation. >> >> The project seems very exciting,and I would consider it and honour to be >> able to do it for PostGreSQL. >> >> Basically,from what I understood,I will be building a fdw which will > invoke >> PL/Java routines which will make JDBC calls to external databases.So,the > fdw >> can be used to access any database that supports JDBC.That will be truly >> awesome. >> >> For connecting the C API and Pl/Java code,we can use JNI(Java Native >> Interface).It's not too stable,but it can work if taken care of. > > That's backwards -- the C code will invoke java, not the other way > around -- so JNI is no help. SPI is a C interface that allows you to > (in C) invoke any function in the database, including those written in > pl/java. That's a possible path to doing this but it's fairly > circuitous since pl/java wold be building the result set only to have > the fdw api tear it down again and rebuild it and there may be other > problems. The main issue here would be to figure out how to hook into > java the best/fastest way from C code. > > Merlin > > --------------- > Hi Merlin, > > I am a bit confused here.Please correct me if I am wrong. > > http://www.codeproject.com/Articles/22881/How-to-Call-Java-Functions-from-C- > Using-JNI > > I found this article.Please see it and guide me. > > Waiting for your reply,
well that might work, but you'd have to think about how this integrates with pl/java which is control of the JVM. ne of the things pl/java does is to manage all the complicated mechanics of running a jvm inside of postgres -- i think a pure JNI route would probably mean not using pl/java. I could be wrong though -- some research and experimentation might be in order. merlin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
