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Re: Why does "update" treat an obstruction differently if adding without history?

From: Julian Foad <julianfoad_at_btopenworld.com>
Date: Thu, 30 Oct 2008 12:54:30 +0000

On Wed, 2008-10-29 at 12:09 -0700, Greg Stein wrote:
> On Wed, Oct 29, 2008 at 9:46 AM, Stephen Butler <sbutler_at_elego.de> wrote:
> > Quoting Greg Stein <gstein_at_gmail.com>:
> >
> >> On Wed, Oct 29, 2008 at 8:03 AM, Stephen Butler <sbutler_at_elego.de> wrote:
> >>>
> >>> ...
> >>> I'm hacking away at the skipping problem, too. For the
> >>> allow-existing-add
> >>> feature, I simply gave check_tree_conflicts() a ptr-to-bool arg. Here's
> >>> the signature for that function in my incomplete patch:
> >>
> >> How big and ugly is that function? update_editor.c has a ton of these
> >> huge nasty functions. The code complexity is really bad.
> >
> > Maybe I've been working in the update-editor mine too long and lost
> > perspective...
>
> Um... is it? or not? If it is a straightforward function, then ignore
> me. But given the lengthy parameter list, I'm guessing "long", so that
> was my question to you.
>
> >> I'm assuming this is similar, and so in that vein:
> >>
> >>> /* First, check whether a significant conflict has already been raised
> >>> * on FULL_PATH. For any incoming change ACTION, check for a tree
> >>> * conflict. When adding an item, text and prop conflicts may also be
> >>> * checked. If an existing conflict is found, return NULL in
> >>> * *PCONFLICT and set *SKIP_P to TRUE.
> >>
> >> Can this first check be broken out into a function, say,
> >> covered_by_existing_conflict(...) ?
> >
> > Yes. Actually, it already is. Doh!
>
> Okay. So it *is*. Does that mean you're going to keep it that way, or
> are you proposing to mush the two together? Not sure what your answer
> meant.
>
> >>> * Second, check whether the incoming change ACTION on FULL_PATH would
> >>> * conflict with FULL_PATH's scheduled change. If so, then FULL_PATH
> >>> * is a new tree conflict victim. Raise a persistent tree conflict by
> >>> * appending log actions to LOG_ACCUM. Return a conflict description
> >>> * in *PCONFLICT and set *SKIP_P to TRUE.
> >>
> >> Rather than taking LOG_ACCUM, can this function instead rely on the
> >> caller to perform log actions. IOW, only *check* for a conflict. Don't
> >> take any actions on it.
> >
> > We could pull out the code that writes the tree conflict data to the
> > parent dir's entry. But if we find a new tree conflict, we always
> > write it.
>
> Hunh? I mean the code that puts stuff into LOG_ACCUM. Can we move that
> code out of this function, thereby not need to take a LOG_ACCUM
> parameter? And thus also making this file a *check* rather than a
> *modify*.
>
> > On a related note, we expect the caller to flush and run the log
> > (for update and switch).
>
> Assumed so, yeah.
>
> >>> * If no conflicts are found, return NULL in *PCONFLICT and set
> >>> * *SKIP_P to FALSE.
> >>> *
> >>> * When adding a file or directory, the KIND is the kind of the item
> >>> * to be added, and *ADD_EXISTED_P will be set to TRUE if the item is
> >>> * already scheduled for add without history (which is not a
> >>> * conflict). For other actions, KIND and ADD_EXISTED_P are ignored.
> >>
> >> Can this be left to the caller? This doesn't seem to be related to
> >> tree conflicts.
> >
> > Actually it is. It's a special case where Subversion automatically
> > resolves a potential tree conflict without raising it.
>
> Alrighty. And I presume the caller needs to know this for some reason.
>
> Would the argument better be named something like ADD_CONFLICT_CLEARED
> ? Or whatever. It seems to suggest that a conflict should be
> *cleared*. Sure, there was an add, but what is the *actual* semantic
> of what happened or should happen?
>
> >>> * The edit baton EB gives information including whether the operation is
> >>> * an update or a switch.
> >>
> >> How many pieces of EB are accessed? Having "the whole EB" can give
> >> this function ugly powers. If you only need one or two parameters,
> >> then I'd suggest passing those directly.
> >
> > Let's see, from the edit baton we need these members for the tree
> > conflict check:
> >
> > allow_unver_obstructions
> > cancel_func
> > cancel_baton
> >
> > And one more for the tree conflict persistence:
> >
> > switch_url (just a boolean if-null check)
> >
> > Not so many after all.
>
> Then I might suggest a couple booleans, and a cancel func/baton pair.
>
> Part of the problem in update_editor is the prevelent use of the
> batons as a pseudo-global variable space. As a result, data flow and
> coupling is near-impossible to track down. I just spent a great number
> of days unwinding some of that around fb->new_text_base_path. After
> unwinding all of that, plus some previous work, I turned *four* passes
> over a file into *one*. We're pretty inefficient :-(
>
> >>> * PARENT_ADM_ACCESS is the admin access baton of FULL_PATH's parent
> >>> * directory.
> >>
> >> Parent? Why not pass the corresponding access baton, and if/when this
> >> function needs it, then it can retrieve it itself. Maybe this is
> >> nomenclature. Consider:
> >>
> >> If kind==file, then is this baton, the directory that the file resides
> >> in? Or the parent of *that* directory?
> >>
> >> If kind==dir, then is this baton related to self, or is this the
> >> parent of the directory?
> >>
> >> Please clarify.
> >
> > It's always the parent dir of the potential tree conflict victim.
>
> Okay. In pseudo-code: get_access_baton(get_dirname(full_path)).
>
> > Should each function retrieve this dir's access baton on its own?
> > Or is it better to pass around the same baton, which the caller
> > can use later (if there's no conflict and the update proceeds)?
>
> Doesn't really matter. The access batons can quickly translate between
> all affected directories. So if you have one, then you have all of
> them.

Steve, the stuff Greg says makes sense to me too :-) I'm not saying you
necessarily have to do all of it.

- Julian

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Received on 2008-10-30 13:54:49 CET

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