• Martin Atkins's avatar
    command/format: improve consistency of plan results · 3ea15929
    Martin Atkins authored
    Previously the rendered plan output was constructed directly from the
    core plan and then annotated with counts derived from the count hook.
    At various places we applied little adjustments to deal with the fact that
    the user-facing diff model is not identical to the internal diff model,
    including the special handling of data source reads and destroys. Since
    this logic was just muddled into the rendering code, it behaved
    inconsistently with the tally of adds, updates and deletes.
    
    This change reworks the plan formatter so that it happens in two stages:
    - First, we produce a specialized Plan object that is tailored for use
      in the UI. This applies all the relevant logic to transform the
      physical model into the user model.
    - Second, we do a straightforward visual rendering of the display-oriented
      plan object.
    
    For the moment this is slightly overkill since there's only one rendering
    path, but it does give us the benefit of letting the counts be derived
    from the same data as the full detailed diff, ensuring that they'll stay
    consistent.
    
    Later we may choose to have other UIs for plans, such as a
    machine-readable output intended to drive a web UI. In that case, we'd
    want the web UI to consume a serialization of the _display-oriented_ plan
    so that it doesn't need to re-implement all of these UI special cases.
    
    This introduces to core a new diff action type for "refresh". Currently
    this is used _only_ in the UI layer, to represent data source reads.
    Later it would be good to use this type for the core diff as well, to
    improve consistency, but that is left for another day to keep this change
    focused on the UI.
    3ea15929