Open Stack

Hi Glance team,

The question is from a bug https://bugs.launchpad.net/glance/+bug/1462315,

If an image-member is deleted, then create it again with the same
parameters, glance searches db to see if there is already an existing one,
but the result doesn't include the record which was marked as deleted,
glance will try to create a new one with the same parameters, it works well
on mysql. But it is failed on DB2 with SQL0803N error.

The root cause is that DB2 constraint is more restricted than mysql. For
db2, the columns under unique constrains should be "NOT NULL", currently
the column "deleted_at" which is one of unique constrain of image_members
is nullable. A possible solution is to alter it to "not null" in migration.
that means we have to insert a default timestamp value for the new created
image-member, an active member with a no-blank timestamp for "deleted_at"
seems very confusing.

Another fix is: we may check all existing image-member records including
the deleted image-member before create image-member, then update it if it
exists, otherwise create a new one, that is proposed in
https://review.openstack.org/#/c/190895/


I'm wondering why can't we use only one record to maintain the member-ship
between a pair of image and tenant. Maybe there is some other
consideration, I'd like to know more. Thanks.


Best regards,
LongQuan
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