| 524 | | Although the ``page.data = data`` statement tells SQLAlchemy to store the page |
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| 525 | | data in the database, nothing happens until the ``DBSession.commit()``. This |
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| 526 | | structure allows SQLAlchemy to combine many operations into a single database |
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| 527 | | transaction and thus be much more efficient. You can also call |
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| 528 | | ``DBSession.flush()`` to send changes to the database, then do more work, then |
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| 529 | | ``flush()`` again, before finally committing. When you do a ``commit()``, that |
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| 530 | | will flush automatically for you if you haven't flushed explicitly. |
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| 531 | | |
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| 532 | | You can now make changes and save the page we were editing, just like a real |
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| | 524 | Although the ``page.data = data`` statement tells SQLAlchemy that you intend to store the page data in the database, nothing happens until the ``DBSession.flush()`` method is called. This is commonly refered to as the "unit of work" pattern, and it's an important structure for database developers because it allows SQLAlchemy to combine many operations into a single database update (or a minimized number of updates if some changes depend upon earlier changes) and thus be much more efficient in the database resources used. |
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| | 525 | |
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| | 526 | SQLALchemy also provides a ``DBSession.commit() method which flushes and commits any changes you've made in a trasaction. TurboGears 2 provides a flexible transaction management system that automates this process wrapping each web request in it's own transaction and automatically rolling back that transaction if you get a python exception, or return an HTTP error code as your response. |
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| | 527 | |
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| | 528 | You don't have to do anything to use this transaction management system, it should just work. So, you can now make changes and save the page we were editing, just like a real |
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