[openstack-dev] [heat] Support for an "undo" operation for migrating back resource_properties_data

Crag Wolfe cwolfe at redhat.com
Thu Sep 1 00:57:50 UTC 2016

I'm working on a migrate utility for
https://review.openstack.org/#/c/363415 . Quick summary: that means
moving resource.properties_data and event.properties_data to a new
table, resource_properties_data. Migrating to the new model is easy. The
questions come up with the inverse operation.

1) Would we even want to support undoing a migrate? I lean towards "no"
but if the answer is "yes," the next question comes up:

2) We need to indicate somewhere which resource_properties_data rows
were migrated to begin with. The reason being, we shouldn't support
trying to migrate recent (non-legacy) resource_properties_data data
backwards into the legacy columns in the resource and event tables.
There are a couple of ways to do that: a) add an is_legacy column to
resource_properties_data b) add another table which stores id's of those
that events and resources that have been migrated or c) for the super
paranoid same as b) only also store an extra copy of the original data
(partially motivated by the unfortunate situation we have of
events.properties_data being a PickleType and something going wrong with
the conversion to a Json column, not that I see that happening). c) also
opens up another can of worms with encrypt/decrypt operations. I lean
towards "b" here (well, after null set ;-).


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