Change in ovirt-engine[master]: engine: remove snapshots table constraints

[Code Review]

>From Tal Nisan <tnisan at redhat.com>:

Tal Nisan has submitted this change and it was merged.

Change subject: engine: remove snapshots table constraints
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engine: remove snapshots table constraints

The RestoreAllSnapshotsCommand is a transactive command.
As part of the flow, first the snapshot entry is locked, then if
needed memory volumes will be deleted.
However, the RemoveDiskCommand is a non-transactive command and when
it will try to delete the memory disk, it will need to update also
the snapshot row that contains the memory disk id.
But since that the snapshot row is already locked by the first
command, the RemoveDiskCommand will fail to get the lock.

This patch remove the constraints between the base_disks and the
snapshots.

A better solution is to make RestoreAllSnapshotsCommand a
non-transactive command, and add compensation logic.

Also, newer version of Postgres will permit better locking, avoiding
this situation.

Bugs:
BZ 1454823:
     Restore the constraints after upgrading the Postgres version.
BZ 1454830:
     Make RestoreAllSnapshotsCommand non-transactive command and add
     compensation logic

Change-Id: Iffc45d2ef28b65894504e49f6e966c81c4a16c3f
Bug-Url: https://bugzilla.redhat.com/1427104
Signed-off-by: Fred Rolland <frolland at redhat.com>
---
A packaging/dbscripts/upgrade/04_02_0270_drop_memory_snapshot_constraints.sql
1 file changed, 2 insertions(+), 0 deletions(-)

Approvals:
  Tal Nisan: Looks good to me, approved; Passed CI tests
  Allon Mureinik: Looks good to me, but someone else must approve
  Freddy Rolland: Verified



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Gerrit-MessageType: merged
Gerrit-Change-Id: Iffc45d2ef28b65894504e49f6e966c81c4a16c3f
Gerrit-PatchSet: 3
Gerrit-Project: ovirt-engine
Gerrit-Branch: master
Gerrit-Owner: Freddy Rolland <frolland at redhat.com>
Gerrit-Reviewer: Allon Mureinik <amureini at redhat.com>
Gerrit-Reviewer: Benny Zlotnik <bzlotnik at redhat.com>
Gerrit-Reviewer: Fred Rolland <frolland at redhat.com>
Gerrit-Reviewer: Freddy Rolland <frolland at redhat.com>
Gerrit-Reviewer: Idan Shaby <ishaby at redhat.com>
Gerrit-Reviewer: Jenkins CI
Gerrit-Reviewer: Liron Aravot <laravot at redhat.com>
Gerrit-Reviewer: Tal Nisan <tnisan at redhat.com>
Gerrit-Reviewer: gerrit-hooks <automation at ovirt.org>