[teiid-issues] [JBoss JIRA] Created: (TEIID-897) Create a new autowrap mode to replace pessimistic/optimistic

[Steven Hawkins (JIRA)]

Create a new autowrap mode to replace pessimistic/optimistic
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                 Key: TEIID-897
                 URL: https://jira.jboss.org/jira/browse/TEIID-897
             Project: Teiid
          Issue Type: Feature Request
          Components: Query Engine
    Affects Versions: 7.0
            Reporter: Steven Hawkins
            Assignee: Steven Hawkins
             Fix For: 7.0


There are issues with pessimistic/optimistic autowrap modes:

1. optimistic transaction autowrap is no longer needed since all installations of Teiid have a transaction manager available.  This mode is really only useful as a development time aid - there is also a case to replace it with a readonly mode to prevent all updates.

2. the detection of when a transaction is needed is based upon the resolved from of a command and not the actual plan/execution.  This has led to progressively more pessimistic logic to capture when a transaction is needed (being fully pessimistic we'd have to assume that any procedure with an update count of 1 also needs a transaction since an error can occur during the conversion of output parameters that should cause a rollback).  We should either do a better job based upon the plan/execution, or just state simple assumptions (select -no txn, source insert, update, delete, exec w/ update count <=1 -no txn, else txn).

3. the terminology is confusing since it's evocative of locking semantics

I therefore propose we change these to txnAutoWrap=AUTO, which would be similar to pessimistic mode and would change the detection strategy to one of the proposals from 2.

We should also be explicit that this mode is based upon the assumption that multiple selects do not need to be grouped in the same transaction.  However when there is a transaction, then the selects will be performed in the same transaction.



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