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Add java mention.
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‎doc/FAQ

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Frequently Asked Questions (FAQ) for PostgreSQL
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Last updated: Tue Aug 21 07:05:48 EDT 2001
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Last updated: Tue Sep 4 01:14:28 EDT 2001
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Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us)
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4.22) How do I create a column that will default to the current time?
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4.23) Why are my subqueries using IN so slow?
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4.24) How do I perform an outer join?
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4.25) How do I perform queries using multiple databases?
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Extending PostgreSQL
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In PostgreSQL 6.5 and up, the default limit is 32 processes. You can
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increase it by restarting the postmaster with a suitable -N value.
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With the default configuration you can set -N as large as 1024. If you
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need more, increase MAXBACKENDS in include/pg_config.h and rebuild. You
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can set the default value of -N at configuration time, if you like,
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using configure's --with-maxbackends switch.
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need more, increase MAXBACKENDS in include/pg_config.h and rebuild.
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You can set the default value of -N at configuration time, if you
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like, using configure's --with-maxbackends switch.
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Note that if you make -N larger than 32, you must also increase -B
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beyond its default of 64; -B must be at least twice -N, and probably
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FROM tab1
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WHERE tab1.col1 NOT IN (SELECT tab2.col1 FROM tab2)
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ORDER BY col1
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4.25) How do I perform queries using multiple databases?
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There is no way to query any database except the current one. Because
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PostgreSQL loads database-specific system catalogs, it is uncertain
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how a cross-database query should even behave.
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Of course, a client can make simultaneous connections to different
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databases and merge the information that way.
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_________________________________________________________________
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Extending PostgreSQL

‎doc/TODO.detail/java

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---------------------------(end of broadcast)---------------------------
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TIP 3: if posting/reading through Usenet, please send an appropriate
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subscribe-nomail command to majordomo@postgresql.org so that your
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message can get through to the mailing list cleanly
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From pgsql-general-owner+M14597@postgresql.org Fri Aug 31 23:23:15 2001
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Return-path: <pgsql-general-owner+M14597@postgresql.org>
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Fri, 31 Aug 2001 22:35:23 -0400 (EDT)
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Date: Fri, 31 Aug 2001 22:35:23 -0400 (EDT)
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From: Alex Pilosov <alex@pilosoft.com>
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To: Alex Knight <knight@phunc.com>
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cc: pgsql-general@postgresql.org
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Subject: [WAY OT] Re: [GENERAL] PL/java?
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In-Reply-To: <MAEFKNDLAHNIFMAIEGHJCEKJCDAA.knight@phunc.com>
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Message-ID: <Pine.BSO.4.10.10108312220140.19501-100000@spider.pilosoft.com>
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MIME-Version: 1.0
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Content-Type: TEXT/PLAIN; charset=US-ASCII
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Precedence: bulk
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Sender: pgsql-general-owner@postgresql.org
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Status: OR
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On Fri, 31 Aug 2001, Alex Knight wrote:
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> It is generally wiser to split the webservers from the appservers;
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> that will save on memory footprints from each respectively. That alone
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> can give each machine a specific task to accomplish... generally more
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> efficiently. But I would assume you know this.
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And it is wise to split database from middleware, and not try to saddle
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PostgreSQL with requirements to support Java in-process. _IF_ java stored
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procedures are implemented, it should be via something like a) oracle's
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extproc (start a separate process to load the function) b) some of perl
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java tools (they start a jdk in a separate process and communicate with it
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using RMI).
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Problem with java-pgsql integration is the threads model: Java really
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really wants threads. Postgres doesn't do threads. So if most simple way
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is attempted, you will incur overhead of starting up JVM for each backend
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(a few seconds as opposed to milliseconds) and non-shared 30M of memory
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per backend (as opposed to currently <3 megs of non-shared memory per
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backend).
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> Using something like WebLogic, WebSphere, or Orion would be a wiser
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> approach. For the company with the low budget, Orion is only something
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> like $2000, and it has full J2EE support, including EJBs, etc. Try
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> finding that kind of richness in Tomcat. Also, Orion takes up only
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> 40-50mb at start, which is really fairly reasonable; ram is cheap
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> anyways... a server that has to perform complicated algorithms to a
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> large audience but has hardly any ram shouldn't be on the internet
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> anyways; unless it can handle it.
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_ONLY_ 40-50Mb?! Egads, I'm hard pressed to find any other piece of
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(non-windows, non-java) software that takes 40-50M just to start up!
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I worked with both CrapLogic and CrapSphere. Weblogic takes 20-60 seconds
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to start up on P3-800, that, IMHO, is ridiculous.
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It is not only issue of memory, its easy to throw memory at the problem,
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its an issue of _incremental use_ of memory. As you scale
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> I feel that you don't really have enough experience with _java_ to
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> judge it accurately. Frankly, the JVM is quite small nowadays,
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> considering the amount of base classes that sit in memory much of the
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> time. And the JVMs are really much faster these days. Java is still
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> slow for 2 reasons: 1) Developers who don't optimize their code as
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> they write it, 2) Bytecode interpretation is and probably never will
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> be as fast as something like C/C++. But it certainly isn't the JVM
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> itself slowing it down because of some "extended memory" that it lives
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> in. Any reasonable server should have absolutely no problems if the
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> jvm is implemented _properly_ (which many packages do not do), etc. If
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> you're comparing Java to perl, yes, certainly it's a bit more of a
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> beast, but perl quite simply can't keep up in speed and feature
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> richness (when was the last time you secured your perl code in a
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> redistributable fashion?)
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_WHY_ the heck do all base classes need to be in memory all the time? Why
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are they so huge? Libc is _far far_ smaller, and libstdc++ is tiny
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compared to all the java standard library.
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You know what the answer to it is: Because they are ALL written in java,
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as opposed to more sane languages like perl which handcode their "standard
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libraries" or the most important pieces of them in C.
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Perl is far faster than java in about any practical application I did.
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Again, the issue is not speed of JVM versus PP (perl virtual machine), if
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you did number crunching in perl and java, they would probably be at par.
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Its an issue of standard libraries. They are _horribly slow_. Perl's
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hashtables are a very nice piece of optimized C code. Java's hashtables
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are written in Java. Need I say more? Java's AWT was a dog. Swing is a dog
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and a half, because they reimplemented all the things that are commonly
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done in C in Java.
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> The only mistake the developers can make is poorly implementing the
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> jvm, but most certainly not Java itself. I've been working on
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> architecting and building enterprise level sites and applications for
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> nearly 8 years now, and I've seen too many people try to implement
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> perl cgi websites for enterprise sites and watch them choke and crawl
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> to their knees because of poor system resource handling, lack of
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> scalability, etc... I most certainly don't consider a single webserver
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> with an appserver and tiny database to be enterprise level either (not
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> that I'm inferring you said it was).
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You cannot compare a perl CGI script and a J2EE server. Its like comparing
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a webserver you wrote yourself vs apache! There are application servers
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(or more closely, code libraries) for perl that match what J2EE provides.
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--
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Alex Pilosov | http://www.acedsl.com/home.html
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CTO - Acecape, Inc. | AceDSL:The best ADSL in the world
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325 W 38 St. Suite 1005 | (Stealth Marketing Works! :)
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New York, NY 10018 |
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