Thread: [Fwd: FAQ update about transaction interleaving]
I posted this some time ago, but no-one reacted, so I'm reposting... Is there a preferred format for FAQ updates? -------- Original Message -------- From: Heikki Linnakangas <heikki@enterprisedb.com> To: pgsql-jdbc@postgresql.org Date: Fri, 29 Sep 2006 16:34:11 +0100 Subject: FAQ update about transaction interleaving Our FAQ entry on XA support is quite vague; most users don't know what transaction interleaving is or why they should care. Here's an updated version based on a response I gave earlier to a post asking about it: ----------------- 1.1. Does the driver have XA support? Yes, starting with the 8.1dev-403 driver. However, the transaction interleaving is not supported. 1.2. What is "transaction interleaving"? Transaction interleaving means that one database connection can be used for multiple transactions at the same time, switching between the transactions. Transaction interleaving is mostly useless, but it's a required part of the JTA specification. Some application servers use it to allow a bit more concurrency without allocating a bigger jdbc connection pool. Few JDBC drivers support transaction interleaving properly. Some fake it by issuing early prepare commands, risking transaction integrity, some give strange error messages, some fail in other, subtle ways. The PostgreSQL JDBC driver does it's best to detect interleaving and throws a proper error message when it can't do what's requested. Because of the lack of driver support, all of the popular application servers use provide options to work around it, or don't use it at all. Therefore, lack of transaction interleaving shouldn't affect your application or data integrity. See the JTA specification, section 3.4.4, or search the pgsql-jdbc mailing list archives for more information. 1.3. How to configure application server XXX to work with the PostgreSQL JDBC driver [We need some examples...] Please read the documentation of your application server for details. You might need to set a flag to disable transaction interleaving. In JBoss, for example, set the "track-connection-by-tx" parameter. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com
I think that the preferred format for FAQ updates is as a patch to the www project's src/documentation/content/xdocs/documentation/faq.xml file from CVS. -- Mark On Fri, 2006-11-10 at 12:33 +0000, Heikki Linnakangas wrote: > I posted this some time ago, but no-one reacted, so I'm reposting... > > Is there a preferred format for FAQ updates? > > -------- Original Message -------- > From: Heikki Linnakangas <heikki@enterprisedb.com> > To: pgsql-jdbc@postgresql.org > Date: Fri, 29 Sep 2006 16:34:11 +0100 > Subject: FAQ update about transaction interleaving > > Our FAQ entry on XA support is quite vague; most users don't know what > transaction interleaving is or why they should care. > > Here's an updated version based on a response I gave earlier to a post > asking about it: > > ----------------- > 1.1. Does the driver have XA support? > > Yes, starting with the 8.1dev-403 driver. However, the transaction > interleaving is not supported. > > 1.2. What is "transaction interleaving"? > > Transaction interleaving means that one database connection can be used > for multiple transactions at the same time, switching between the > transactions. > > Transaction interleaving is mostly useless, but it's a required part of > the JTA specification. Some application servers use it to allow a bit > more concurrency without allocating a bigger jdbc connection pool. > > Few JDBC drivers support transaction interleaving properly. Some fake it > by issuing early prepare commands, risking transaction integrity, some > give strange error messages, some fail in other, subtle ways. The > PostgreSQL JDBC driver does it's best to detect interleaving and throws > a proper error message when it can't do what's requested. > > Because of the lack of driver support, all of the popular application > servers use provide options to work around it, or don't use it at all. > Therefore, lack of transaction interleaving shouldn't affect your > application or data integrity. > > See the JTA specification, section 3.4.4, or search the pgsql-jdbc > mailing list archives for more information. > > 1.3. How to configure application server XXX to work with the PostgreSQL > JDBC driver > > [We need some examples...] > > Please read the documentation of your application server for details. > You might need to set a flag to disable transaction interleaving. In > JBoss, for example, set the "track-connection-by-tx" parameter. > >
Mark Lewis wrote: > I think that the preferred format for FAQ updates is as a patch to the > > www project's src/documentation/content/xdocs/documentation/faq.xml file > from CVS. Ok, thanks. Here you go. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com ? xa-faq-update.diff Index: src/documentation/content/xdocs/documentation/faq.xml =================================================================== RCS file: /usr/local/cvsroot/pgjdbc/www/src/documentation/content/xdocs/documentation/faq.xml,v retrieving revision 1.3 diff -c -r1.3 faq.xml *** src/documentation/content/xdocs/documentation/faq.xml 26 Sep 2006 05:14:10 -0000 1.3 --- src/documentation/content/xdocs/documentation/faq.xml 10 Nov 2006 16:23:38 -0000 *************** *** 10,18 **** <question>Does the driver have XA support?</question> <answer> <p> ! Yes, starting with the 8.1dev-403 driver XADataSource support ! is available. It is not complete in that it does not support ! transaction interleaving. </p> </answer> </faq> --- 10,49 ---- <question>Does the driver have XA support?</question> <answer> <p> ! Yes, starting with the 8.1dev-403 driver. However, transaction ! interleaving is not supported. ! </p> ! </answer> ! <question>What is "transaction interleaving"?</question> ! <answer> ! <p> ! Transaction interleaving means that one database connection can be ! used for multiple transactions at the same time, switching between ! the transactions. ! </p> ! <p> ! Transaction interleaving is mostly useless, but it's a required part ! of the JTA specification. Some application servers use it to allow a ! bit more concurrency without allocating a bigger jdbc connection ! pool. ! </p> ! <p> ! Few JDBC drivers support transaction interleaving properly. Some ! fake it by issuing early prepare commands, risking transaction ! integrity, some give strange error messages, some fail in other, ! subtle ways. The PostgreSQL JDBC driver does it's best to detect ! interleaving and throws a proper error message when it can't do ! what's requested. ! </p> ! <p> ! Because of the lack of driver support, all of the popular application ! servers provide options to work around it, or don't use it at all. ! Therefore, lack of transaction interleaving shouldn't affect your ! application or data integrity. ! </p> ! <p> ! See the JTA specification, section 3.4.4, or search the pgsql-jdbc ! mailing list archives for more information. </p> </answer> </faq>