Re: [boost] [std_rdb] [rdb] 0.0.09

Subject: Re: [boost] [std_rdb] [rdb] 0.0.09
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-09-30 11:37:11

Jean-Louis Leroy wrote:
>
> my plan is
> to support native bindings. In ODBC a transaction looks like this :
>
>     set autocommit off
>     do work
>     commit or roll back
>     do work
>     commit or roll back
>     etc
>
> This pattern is directly reflected in the current implementation. See
> the test suite in libs/rdb/test/test_odbc.cpp.
>
> Other vendors may have a different pattern :
>
>     begin transaction
>     do work
>     commit or roll back
>      begin transaction
>     do work
>     commit or roll back

If you provide an RAII class that does a start/begin/whatever in the ctor, a roll back in the dtor unless cancelled or committed, and provides member functions to commit or cancel on demand, then all back end schemes should be covered.

The ctor can throw an exception should a particular back end not support transactions.

Whether a back end supports nested transactions or not puts a wrinkle in the abstraction, of course.  I suggest that you model nested transactions and simulate them for back ends that don't support them.  In the latter case, the transaction class must use functions in some implementation layer that will track outstanding "nested" transaction objects in order to correctly decide whether to actually roll back when a transaction object's dtor runs or when commit() and roll_back() are called based upon what has already happened to the underlying, tracked state.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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