SAWarning: The IN-predicate on tags.tag was invoked with an empty sequence

[Sergey Nikitin]

When the 'to_delete' list of instance tags in db method instance_tag_set() is empty, warnings are printed in the nova logs:

SAWarning: The IN-predicate on "tags.tag" was invoked with an empty sequence. This results in a contradiction, which nonetheless can be expensive to evaluate. Consider alternative strategies for improved performance.

The fix is to not query the DB in that case.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/207832

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/207832
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=edd01dc079accd31acf202189f78b5fc1eadb735
Submitter: Jenkins
Branch: master

commit edd01dc079accd31acf202189f78b5fc1eadb735
Author: Sergey Nikitin <email address hidden>
Date: Fri Jul 31 13:34:52 2015 +0300

    Don't query database with an empty list of tags for IN clause

    It raises SAWarning "The IN-predicate on tags.tag was invoked
    with an empty sequence".

    Closes-Bug: #1480226

    Change-Id: Id8fbd92618725f05d32f640f405db9edb0c3e6e5