408 lines
18 KiB
Plaintext
408 lines
18 KiB
Plaintext
From pgsql-hackers-owner+M4145@postgresql.org Sat Feb 3 05:54:06 2001
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(envelope-from peter@retep.org.uk)
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Date: Sat, 03 Feb 2001 10:46:24 +0000
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To: Alex Pilosov <alex@pilosoft.com>, tomasz konefal <twkonefal@yahoo.ca>
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From: Peter Mount <peter@retep.org.uk>
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Subject: Re: [HACKERS] TODO list: Allow Java server-side programming
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Cc: pgsql-hackers@postgresql.org
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In-Reply-To: <Pine.BSO.4.10.10102021453160.9372-100000@spider.pilosoft.c
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om>
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References: <20010202194049.38902.qmail@web12003.mail.yahoo.com>
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Status: OR
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At 14:57 02/02/01 -0500, Alex Pilosov wrote:
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>On Fri, 2 Feb 2001, tomasz konefal wrote:
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>
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> > could someone please clarify what "Allow Java
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> > server-side programming" actually means? what are the
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> > limitations of using java and jdbc with pgsql?
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>
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>It means to embed Java interpreter inside postgres, and allow writing
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>stored procedures and triggers in Java.
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Thats correct. Basically you are talking of something like PL/Java. The
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Java side would be simple, but its linking the JVM to the backend that's
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the problem.
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It's been a while since I delved into the backend, but unless it's changed
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from fork() to threading, I don't really see this happening, unless someone
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who knows C that well knows of a portable way of communicating between two
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processes - other than RMI. If that could be solved, then you could use JNI
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to interface the JVM.
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I know some people think this would slow the backend down, but it's only
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the instanciation of the JVM thats slow, hence the other reason fork() is
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holding this back. Ideally you would want the JVM to be running with
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PostMaster, and then each backend can then use the JVM as and when necessary.
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Obviously you wouldn't want a JVM in every installation, but there are a
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lot of good reasons to have this capability. For example, as part of the
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course I did this week, we used Tomcat (Servlet/JSP/Web server). Now
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there's no reason why Tomcat could run within the same JVM. JBoss is
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another good example (EJB Server). The JBoss team have actually got Tomcat
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to run within the same JVM. Doesn't hinder performance at all, but does
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reduce the memory footprint.
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This is a good future thing to look into (why not for 8.0 ;-) ). If we
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could find an _optional_ way of hooking the backend direct into the JVM, we
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could get PostgreSQL into a lot of new areas. It also would make things
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like CORBA etc a doddle.
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PS: I'm writing down notes of the course to go onto the JDBC web site this
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weekend, so there's some nice things for EJB, RMI, Corba etc.
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More later, Peter
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From pgsql-hackers-owner+M4153@postgresql.org Sat Feb 3 11:54:12 2001
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Date: Sat, 3 Feb 2001 17:56:33 +0100 (CET)
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From: Peter Eisentraut <peter_e@gmx.net>
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To: Peter Mount <peter@retep.org.uk>
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cc: Alex Pilosov <alex@pilosoft.com>, tomasz konefal <twkonefal@yahoo.ca>,
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<pgsql-hackers@postgresql.org>
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Subject: Re: [HACKERS] TODO list: Allow Java server-side programming
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In-Reply-To: <5.0.2.1.0.20010203103036.009efec0@mail.retep.org.uk>
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Message-ID: <Pine.LNX.4.30.0102031746220.8648-100000@peter.localdomain>
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Status: OR
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Peter Mount writes:
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> Thats correct. Basically you are talking of something like PL/Java. The
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> Java side would be simple, but its linking the JVM to the backend that's
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> the problem.
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I've tried that recently, here's how it looks as far as Linux JVMs go:
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* Kaffe has a very polluted name space. Calls to its own functions get
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resolved to PostgreSQL, and vice versa. Crash and burn result. The Kaffe
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folks have admitted that this should be fixed but I didn't look farther
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yet.
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* The Sun/Blackdown JVM didn't work at all (not even 'java -version')
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until I upgraded my libc. Then a simple test run crashes with an "error
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external to JVM"; at first it looked like a segfault when referencing a
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string constant. In gdb I saw myself faced with about 10 threads running
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when nothing was going on yet, at which point I was too exhausted to
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proceed.
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* IBM's offering didn't work at all. I don't recall the problem anymore
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but I think it didn't even link correctly.
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So currently I don't see how this could become a mainstream project, let
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alone across platforms.
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> I know some people think this would slow the backend down, but it's only
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> the instanciation of the JVM thats slow, hence the other reason fork() is
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> holding this back. Ideally you would want the JVM to be running with
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> PostMaster, and then each backend can then use the JVM as and when necessary.
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But how do the other languages cope? Starting up a new Perl for each
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backend can't be so cheap either.
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--
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Peter Eisentraut peter_e@gmx.net http://yi.org/peter-e/
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From pgsql-hackers-owner+M4154@postgresql.org Sat Feb 3 12:37:02 2001
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Sat, 3 Feb 2001 12:36:01 -0500 (EST)
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Date: Sat, 3 Feb 2001 12:36:01 -0500 (EST)
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From: Alex Pilosov <alex@pilosoft.com>
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To: Peter Mount <peter@retep.org.uk>
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cc: Alex Pilosov <alex@pilosoft.com>, tomasz konefal <twkonefal@yahoo.ca>,
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pgsql-hackers@postgresql.org
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Subject: Re: [HACKERS] TODO list: Allow Java server-side programming
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In-Reply-To: <5.0.2.1.0.20010203103036.009efec0@mail.retep.org.uk>
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Status: OR
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On Sat, 3 Feb 2001, Peter Mount wrote:
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> It's been a while since I delved into the backend, but unless it's
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> changed from fork() to threading, I don't really see this happening,
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> unless someone who knows C that well knows of a portable way of
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> communicating between two processes - other than RMI. If that could be
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> solved, then you could use JNI to interface the JVM.
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There are many ways one can do this:
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a) each backend will have a JVM linked in (shared object). This is the
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way perl/tcl/ruby is embedded, and it works pretty nice. But, Java
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['s memory requirement] sucks, therefore, this may not be the optimal
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way.
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> I know some people think this would slow the backend down, but it's
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> only the instanciation of the JVM thats slow, hence the other reason
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> fork() is holding this back. Ideally you would want the JVM to be
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> running with PostMaster, and then each backend can then use the JVM as
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> and when necessary.
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b) since JVM is threaded, it may be more efficient to have a dedicated
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process running JVM, and accepting some sort of IPC connections from
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postgres processes. The biggest problem here is SPI, there aren't a good
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way for that JVM to talk back to database.
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c) temporarily, to have quick working code, you can reach java using hacks
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using programming languages already built into postgres. Both TCL (tcl
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blend) and Perl (JPL and another hack which name escapes me) are able to
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execute java code. SPI is possible, I think both of these bindings are
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two-way (you can go perl-java-perl-java). Might be worth a quick try?
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-alex
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From pgsql-hackers-owner+M4164@postgresql.org Sun Feb 4 04:23:42 2001
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Date: Sun, 04 Feb 2001 11:18:09 +0200
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From: Hannu Krosing <hannu@tm.ee>
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To: Peter Mount <peter@retep.org.uk>
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CC: Alex Pilosov <alex@pilosoft.com>, tomasz konefal <twkonefal@yahoo.ca>,
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pgsql-hackers@postgresql.org
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Subject: Re: [HACKERS] TODO list: Allow Java server-side programming
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References: <20010202194049.38902.qmail@web12003.mail.yahoo.com> <5.0.2.1.0.20010203103036.009efec0@mail.retep.org.uk>
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Status: OR
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Peter Mount wrote:
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>
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> At 14:57 02/02/01 -0500, Alex Pilosov wrote:
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> >On Fri, 2 Feb 2001, tomasz konefal wrote:
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> >
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> > > could someone please clarify what "Allow Java
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> > > server-side programming" actually means? what are the
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> > > limitations of using java and jdbc with pgsql?
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> >
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> >It means to embed Java interpreter inside postgres, and allow writing
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> >stored procedures and triggers in Java.
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>
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> Thats correct. Basically you are talking of something like PL/Java. The
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> Java side would be simple, but its linking the JVM to the backend that's
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> the problem.
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>
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> It's been a while since I delved into the backend, but unless it's changed
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> from fork() to threading,
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Someone posted here recently his port/tweaks of backend so that it used
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threads instead of fork(). IIRC it was done to be used inside a java
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client in an embedded system.
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----------------
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Hannu
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From pgsql-hackers-owner+M4168@postgresql.org Sun Feb 4 06:54:27 2001
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Date: Sun, 04 Feb 2001 11:51:21 +0000
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To: Peter Eisentraut <peter_e@gmx.net>
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From: Peter Mount <peter@retep.org.uk>
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Subject: Re: [HACKERS] TODO list: Allow Java server-side programming
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Cc: Alex Pilosov <alex@pilosoft.com>, tomasz konefal <twkonefal@yahoo.ca>,
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<pgsql-hackers@postgresql.org>
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In-Reply-To: <Pine.LNX.4.30.0102031746220.8648-100000@peter.localdomain>
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References: <5.0.2.1.0.20010203103036.009efec0@mail.retep.org.uk>
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Status: OR
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At 17:56 03/02/01 +0100, Peter Eisentraut wrote:
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>Peter Mount writes:
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>
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> > Thats correct. Basically you are talking of something like PL/Java. The
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> > Java side would be simple, but its linking the JVM to the backend that's
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> > the problem.
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>
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>I've tried that recently, here's how it looks as far as Linux JVMs go:
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[snip]
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>So currently I don't see how this could become a mainstream project, let
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>alone across platforms.
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I don't think it would be, but it would be a good side-project. Over time
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the various JVM's should become better to interface with.
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|
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> > I know some people think this would slow the backend down, but it's only
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> > the instanciation of the JVM thats slow, hence the other reason fork() is
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> > holding this back. Ideally you would want the JVM to be running with
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> > PostMaster, and then each backend can then use the JVM as and when
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> necessary.
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>
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>But how do the other languages cope? Starting up a new Perl for each
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>backend can't be so cheap either.
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But a lot cheaper than Java.
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Peter
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From pgsql-hackers-owner+M4169@postgresql.org Sun Feb 4 06:57:24 2001
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Received: from mail.postgresql.org (webmail.postgresql.org [216.126.85.28])
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(envelope-from peter@retep.org.uk)
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Received: from heather.retep.org.uk ([193.113.241.180])
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by mail.retep.org.uk (8.11.1/8.11.1) with ESMTP id f14BtjR83557;
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Sun, 4 Feb 2001 06:55:45 -0500 (EST)
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(envelope-from peter@retep.org.uk)
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Message-Id: <5.0.2.1.0.20010204115139.009f1c50@mail.retep.org.uk>
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Date: Sun, 04 Feb 2001 11:54:20 +0000
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To: Alex Pilosov <alex@pilosoft.com>
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From: Peter Mount <peter@retep.org.uk>
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Subject: Re: [HACKERS] TODO list: Allow Java server-side programming
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Cc: Alex Pilosov <alex@pilosoft.com>, tomasz konefal <twkonefal@yahoo.ca>,
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pgsql-hackers@postgresql.org
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In-Reply-To: <Pine.BSO.4.10.10102031220470.10437-100000@spider.pilosoft.
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com>
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References: <5.0.2.1.0.20010203103036.009efec0@mail.retep.org.uk>
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Precedence: bulk
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Sender: pgsql-hackers-owner@postgresql.org
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Status: OR
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At 12:36 03/02/01 -0500, Alex Pilosov wrote:
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>On Sat, 3 Feb 2001, Peter Mount wrote:
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[snip]
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> > I know some people think this would slow the backend down, but it's
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> > only the instanciation of the JVM thats slow, hence the other reason
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> > fork() is holding this back. Ideally you would want the JVM to be
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> > running with PostMaster, and then each backend can then use the JVM as
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> > and when necessary.
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>b) since JVM is threaded, it may be more efficient to have a dedicated
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>process running JVM, and accepting some sort of IPC connections from
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>postgres processes. The biggest problem here is SPI, there aren't a good
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>way for that JVM to talk back to database.
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That was my other idea, but it is the IPC thats problematical. You would
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still need to do some native api to implement some messaging system between
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the two.
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However, at the other extreme there is RPC, which is possible now, but
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would be a lot slower.
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>c) temporarily, to have quick working code, you can reach java using hacks
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>using programming languages already built into postgres. Both TCL (tcl
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>blend) and Perl (JPL and another hack which name escapes me) are able to
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>execute java code. SPI is possible, I think both of these bindings are
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>two-way (you can go perl-java-perl-java). Might be worth a quick try?
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Might be one way to go...
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Peter
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>-alex
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>
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