On Wed, Mar 21, 2012 at 12:42 AM, Merlin Moncure <mmonc...@gmail.com> wrote: > 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
--------------------------- Hi Merlin, Thanks for your reply. Yes,I agree that a pure JNI routine would not be too helpful.I'll try to hook directly onto the JVM in PL/Java.That way,JNI can help us. Please let me know how to proceed further. Atri -- Regards, Atri l'apprenant -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
