Don't use ModelBase.save() inside of block session.begin()

[ChangBo Guo(gcb)]

Current code use ModelBase.save() always submit a commit even inside a block fo with session.begin().
this is not purpose of using session.begin() to organize some operations in one transaction

1)session.begin() will return a SessionTransaction instance, then call SessionTransaction.__enter__()
and do something in with block, then call SessionTransaction.__exit__(), in method __exit__() will commit or rollback automatically. See https://github.com/zzzeek/sqlalchemy/blob/master/lib/sqlalchemy/orm/session.py#L454

2) There is also suggestion metioned in https://github.com/openstack/oslo-incubator/blob/master/openstack/common/db/sqlalchemy/session.py#L71

3) ModelBase.save() begin another transaction see https://github.com/openstack/oslo-incubator/blob/master/openstack/common/db/sqlalchemy/models.py#L47

so we'd better don't use ModelBase.save() inside of block session.begin()

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/46253

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/46258
Committed: http://github.com/stackforge/savanna/commit/9390ce7b035a7d60d0c665dc0891b67f7436e8f3
Submitter: Jenkins
Branch: master

commit 9390ce7b035a7d60d0c665dc0891b67f7436e8f3
Author: Chang Bo Guo <email address hidden>
Date: Thu Sep 12 04:45:31 2013 -0700

    Don't use ModelBase.save() inside of transaction

    We using block 'with session.begin()' to organize some operations in
    one transaction. session.begin() returns a transaction instance, then
    does some operations, and will commit or rollback automatically
    before leaving the block. ModelBase.save() always submit a commit,
    and that is not expected.
    When we get a persistent object from database, we just modify the
    object inside of block 'with session.begin()' and sqlalchemy will
    update it,don't need method session.add() or ModelBase.save()

    Fixes bug #1224429

    Change-Id: I2204b3023c01e65950e6131cd08b4ded5564e9b9

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/46253
Committed: http://github.com/openstack/nova/commit/037d1e9b1b89fb0a969b1b02ee4c74550b7864b0
Submitter: Jenkins
Branch: master

commit 037d1e9b1b89fb0a969b1b02ee4c74550b7864b0
Author: Chang Bo Guo <email address hidden>
Date: Thu Sep 12 04:27:40 2013 -0700

    Don't use ModelBase.save() inside of transaction

    We using block 'with session.begin()' to organize some operations in
    one transaction. session.begin() returns a transaction instance, then
    does some operations, and will commit or rollback automatically
    before leaving the block. ModelBase.save() always submit a commit,
    and that is not expected.
    When we get a persistent object from database, we just modify the
    object inside of block 'with session.begin()' and sqlalchemy will
    update it,don't need method session.add() or ModelBase.save()

    Fixes bug #1224429

    Change-Id: I8af3fd4b62a915833bf303b6892d432043fb57a9

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/78141

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/78141
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=13387c01390e70c9d7811760e603e6306d6d7ea7
Submitter: Jenkins
Branch: master

commit 13387c01390e70c9d7811760e603e6306d6d7ea7
Author: ChangBo Guo(gcb) <email address hidden>
Date: Wed Mar 5 17:00:58 2014 +0800

    Don't use ModelBase.save() inside of transaction

    'with session.begin()' makes some operations in one transaction.
    session.begin() returns a transaction instance, then does some operations,
    and will commit or rollback automatically before leaving the block.
    ModelBase.save() always submit a commit, and that is not expected.
    When we get a persistent object from database, we just modify the
    object inside of block 'with session.begin()' and sqlalchemy will
    update it, don't need method session.add() or ModelBase.save().

    Closes-Bug: #1224429
    Change-Id: I4af58e98b2783d3945d92e57680d58e7ae356a67