Ticket #1077 (new enhancement) — at Version 5

Opened 3 years ago

Last modified 23 months ago

Move to simpler vdm system

Reported by: rgrp Owned by: kindly
Priority: awaiting triage Milestone: ckan-backlog
Component: ckan Keywords:
Cc: Repository: ckan
Theme: none

Description (last modified by rgrp) (diff)

Option 1: 'Changeset' Model

See ticket:1135 for vdm ticket. This would involve a) moving to changeset in vdm b) doing the migration in ckan to support this.

Have developed a new "changeset" based model for revisioning in vdm.

Implementation

  • The main challenge with this change is schema and data migration

Every revisioned object has a revision_id and revision attribute.

Approximate algorithm:

Revision -> Changeset

for revtype in [PackageRevision, ...]:
    for pkgrev in package_revision:
        changeset = lookupchangeset(package_revision)
        ChangeObject(cset, (table, id), dictize(pkgrev))

Question:

  • does pkg include tags attributes or not? or we have to dictize, pkgrev, pkg2tagrev, and tag. Probably the latter.

Option 2: Simplify Revision Object Model

Just use a simpler vdm, see ticket:1136 (move to SessionExtension) and ticket:1137 (remove need for statefulness in vdm).

Discussion

Advantage of Option 1 versus 2:

  • Easier support for pending state and similar behaviour
  • No need to introduce new tables (and hence migrations) when making something revisioned (or not).

Disadvantages

  • Migration is required
  • More difficult to query revision history.
    • Could be addressed by having ChangeObject have separate cols for table name and id but would likely be more difficult.
  • Performance (?)
    • Have one big ChangeObject table to query when looking at changed objects rather than many revision tables.
      • Not sure this is a biggie as even with Revision model biggest revision object tables are probably on the order of the ChangeObject table

Conclusion

Implement Option 2 and leave Option 1 for present.

Option 1 includes Option 2 so it seems that that is required in either case (so we may as well with Option 2).

Option 1 requires significant effort (esp migration) so leave for present and then review the situation at some later date.

Change History

comment:1 Changed 3 years ago by rgrp

  • Priority changed from awaiting triage to critical
  • Description modified (diff)

comment:2 Changed 3 years ago by kindly

  • Description modified (diff)

comment:3 Changed 3 years ago by rgrp

  • state set to draft
  • Description modified (diff)

comment:4 Changed 3 years ago by kindly

  • Description modified (diff)

comment:5 Changed 3 years ago by rgrp

  • Description modified (diff)
  • Summary changed from Switch to new vdm changeset model to Move to simpler vdm system
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