document / provide clear path for custom SQL constructs that support autocommit

[Former user]

Following advice on http://www.sqlalchemy.org/docs/core/compiler.html I create a custom InsertFromSelect element. Unfortunately it seems that it doesn't make the actual insert, even though the SQL generated looks fine.

From a shallow look it seems no COMMIT-statement is issued when InsertFromSelect is executed.

It works fine, if instead of subclassing Executable, ClauseElement, we subclass UpdateBase.

See attached unittest-script for the code to recreate and "resolve" the problem.

[Mike Bayer]

since you're using connectionless execution with no transaction you need to apply autocommit to the construct in order for it to autocommit.

class InsertFromSelect(Executable, ClauseElement):
    _execution_options = \
        Executable._execution_options.union({'autocommit': True})

or:

insert = insert.execution_options(autocommit=True)

the path here should be clearer somehow, either AutocommitExecutable, or something like that.

[Mike Bayer]

we've had the _execution_options workaround documented for quite some time now so that's what we'll keep for now.

[Mike Bayer]

Removing milestone: 0.7.5 (automated comment)