XA end then join fix for WebLogic

Jan de Visser ran into problems with our XA implementation earlier, and
traced the problem to the sequence of XADataSource method calls that
WebLogic performed. He fixed it with a simple patch that allows
start(.., TMJOIN) on a transaction that was ended earlier using the same
connection:

http://archives.postgresql.org/pgsql-jdbc/2005-12/msg00038.php

It puzzles me why WebLogic does that, but it seems valid and we should
support it, even though we can't support join in general.

Here's a more polished version of Jan's patch. I don't have WebLogic to
test this with, so I would appreciate if those that have access to
WebLogic could reproduce the original problem and confirm that this
patch fixes it.

--
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com
Index: org/postgresql/test/xa/XADataSourceTest.java
===================================================================
RCS file: /usr/local/cvsroot/pgjdbc/pgjdbc/org/postgresql/test/xa/XADataSourceTest.java,v
retrieving revision 1.6
diff -c -r1.6 XADataSourceTest.java
*** org/postgresql/test/xa/XADataSourceTest.java    26 Apr 2006 18:58:59 -0000    1.6
--- org/postgresql/test/xa/XADataSourceTest.java    2 Oct 2006 11:32:27 -0000
***************
*** 217,222 ****
--- 217,232 ----
          xaRes.rollback(xid);
      }

+     public void testEndThenJoin() throws XAException {
+         Xid xid = new CustomXid(5);
+
+         xaRes.start(xid, XAResource.TMNOFLAGS);
+         xaRes.end(xid, XAResource.TMSUCCESS);
+         xaRes.start(xid, XAResource.TMJOIN);
+         xaRes.end(xid, XAResource.TMSUCCESS);
+         xaRes.commit(xid, true);
+     }
+
      /* We don't support transaction interleaving.
      public void testInterleaving1() throws Exception {
       Xid xid1 = new CustomXid(1);
Index: org/postgresql/xa/PGXAConnection.java
===================================================================
RCS file: /usr/local/cvsroot/pgjdbc/pgjdbc/org/postgresql/xa/PGXAConnection.java,v
retrieving revision 1.7
diff -c -r1.7 PGXAConnection.java
*** org/postgresql/xa/PGXAConnection.java    26 Apr 2006 18:58:59 -0000    1.7
--- org/postgresql/xa/PGXAConnection.java    2 Oct 2006 11:32:28 -0000
***************
*** 79,86 ****
       * 4. the TM hasn't seen the xid before
       *
       * Implementation deficiency preconditions:
!      * 1. flags must be TMNOFLAGS
!      * 2. Previous transaction using the connection must be committed or prepared or rolled back
       *
       * Postconditions:
       * 1. Connection is associated with the transaction
--- 79,89 ----
       * 4. the TM hasn't seen the xid before
       *
       * Implementation deficiency preconditions:
!      * 1. TMRESUME not supported.
!      * 2. if flags is TMJOIN, we must be in ended state,
!      *    and xid must be the current transaction
!      * 3. unless flags is TMJOIN, previous transaction using the
!      *    connection must be committed or prepared or rolled back
       *
       * Postconditions:
       * 1. Connection is associated with the transaction
***************
*** 102,110 ****
          // We can't check precondition 4 easily, so we don't. Duplicate xid will be catched in prepare phase.

          // Check implementation deficiency preconditions
!         if (flags != TMNOFLAGS)
!             throw new PGXAException(GT.tr("suspend/resume and join not implemented"), XAException.XAER_RMERR);
!         if (state == STATE_ENDED)
              throw new PGXAException(GT.tr("Transaction interleaving not implemented"), XAException.XAER_RMERR);

          // Preconditions are met, Associate connection with the transaction
--- 105,122 ----
          // We can't check precondition 4 easily, so we don't. Duplicate xid will be catched in prepare phase.

          // Check implementation deficiency preconditions
!         if (flags == TMRESUME)
!             throw new PGXAException(GT.tr("suspend/resume not implemented"), XAException.XAER_RMERR);
!
!         // It's ok to join an ended transaction. WebLogic does that.
!         if (flags == TMJOIN)
!         {
!             if (state != STATE_ENDED)
!                 throw new PGXAException(GT.tr("Transaction interleaving not implemented"), XAException.XAER_RMERR);
!
!             if (!xid.equals(currentXid))
!                 throw new PGXAException(GT.tr("Transaction interleaving not implemented"), XAException.XAER_RMERR);
!         } else if(state == STATE_ENDED)
              throw new PGXAException(GT.tr("Transaction interleaving not implemented"), XAException.XAER_RMERR);

          // Preconditions are met, Associate connection with the transaction