http://www.slony.info/bugzilla/show_bug.cgi?id=333

           Summary: Deadlock with application during minor version
                    upgrade.
           Product: Slony-I
           Version: devel
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: low
         Component: slonik
        AssignedTo: slony1-bugs at lists.slony.info
        ReportedBy: janwieck at yahoo.com
                CC: slony1-bugs at lists.slony.info
   Estimated Hours: 0.0


The Slony upgrade procedure for minor versions can collide with concurrently
running applications, even with read only transactions.

During the upgrade the stored procedures to upgrade the schema configure all
log and deny access triggers. This is done with an "ALTER TABLE ...
ENABLE/DISABLE TRIGGER ..." command. This command requires an access exclusive
lock on the table, which conflicts even with read only access.

This command could be skipped if the trigger in question is already configured
in that enable/disable state, which can be determined by a lookup in
pg_trigger. I believe that during a pure minor version upgrade, none of the
triggers actually needs to be reconfigured since they all should be in the
desired state already.

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