> Found the problem. It's in the PostgreSQL "valid connection checker" class
> provided by JBoss. A typical JBoss data source configuration file for
> PostgreSQL
> includes the following XML:
>
>
> <valid-connection-checker-class-name>org.jboss.resource.adapter.jdbc.vendor.PostgreSQLValidConnectionChecker</valid-connection-checker-class-name>
>
> The source code for the PostgreSQLValidConnectionChecker class includes the
> following validity check:
>
> try
> {
> stmt = cn.createStatement();
> stmt.execute("");
> }
> // etc..
>
> This empty-string query is exactly what's causing the problem. When I
> disable the connection checker by commenting out the XML element shown above,
> everything works correctly.
>
> Apparently, this JBoss behavior is intentional, for performance reasons that
> came from discussing with PostgreSQL developers. See
> https://issues.jboss.org/browse/JBAS-3133 and
> http://community.jboss.org/message/298853#298853 for details.
>
> At any rate, I *strongly* recommend including this information in the
> pgpool-II documentation. The current version of JBoss (AS 7) still has this
> code (see
> https://source.jboss.org/browse/JBossAS/connector/src/main/java/org/jboss/as/connector/adapters/jdbc/extensions/postgres/PostgreSQLValidConnectionChecker.java?r=6c64725de60a324628dc648baae080a9a7516dca).
Thank you for the info. I will add up to FAQ about this (adding to
official docs may not be usefull since the info will be not be given
to the user who have same probalem as you until they upgrade
pgpool-II).
Of course we will look into the problem you pointed out in the mean time.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp
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