Why are 'select1; commit' run along with 'set autocommit=on' when turning autocommit on again on a jdbc connection

Hi,

I am working with Postgres 7.3 using jdbc driver pg73jdbc3.jar. On acquiring
a jdbc connection, if auto commit is turned off and then turned on again,
with log_statements=true uncommented in postgresql.conf, the following set
of statements are logged in the database log file:

LOG:  query: set datestyle to 'ISO'; select version(), case when
pg_encoding_to_char(1) = 'SQL_ASCII' then 'UNKNOWN' else
getdatabaseencoding() end;
LOG:  query: set client_encoding = 'UNICODE'; show autocommit
LOG:  query: set autocommit = off;
LOG:  query: select 1;
LOG:  query: commit; set autocommit = on;

Why does the postgres jdbc driver execute 'select 1' and 'commit' followed
by 'set autocommit = on'? Setting autocommit on again should just result in
'set autocommit=on' statement to be executed, not 'select 1' and 'commit'.
User would not expect commit to be issued by just turning autocommit on and
thus its execution here alarms me.

I have included the test class I wrote which takes host, port, dbname, user
and password as command line arguments. I have the pg73jdbc3.jar in my
classpath when I run the test class.

import java.sql.*;

public class TestAutoCommit
{
  public static void main(String[] args) throws SQLException
  {
    if (args.length != 5)
    {
      System.out.println("USAGE: java TestAutoCommit <jdbc_host> <port> <db>
<user> <password>");
      return;
    }

    String host = args[0];
    String port = args[1];
    String db   = args[2];
    String user = args[3];
    String pswd = args[4];

    String connectUrl = "jdbc:postgresql://" + host + ":" + port + "/" + db
+ "?user=" + user + "&password=" + pswd;
    String driverClassName="org.postgresql.Driver";

    System.out.println("Connection Details:\n URL = " + connectUrl +
                       "\n Driver ClassName = " + driverClassName +
                       "\n User = " + user + "\n Password = " + pswd +
"\n");

    try { Class.forName(driverClassName); }
    catch (Exception e)
    {
      System.out.println("Can't register JDBC driver: " + driverClassName +
                         ", Exception: " + e);
    }

    Connection dbCon = DriverManager.getConnection(connectUrl, user, pswd);
    dbCon.setAutoCommit(false);
    dbCon.setAutoCommit(true);
    dbCon.close();
  }
}

Regards,
Vrinda Mushran