[PATCH] revset: introduce optional 'while' predicate for ancestors()

[Mads Kiilerich]

On 10/08/2014 03:27 AM, Pierre-Yves David wrote:
>
>
> On 10/07/2014 05:22 PM, Mads Kiilerich wrote:
>> # HG changeset patch
>> # User Mads Kiilerich <madski at unity3d.com>
>> # Date 1412727753 -7200
>> #      Wed Oct 08 02:22:33 2014 +0200
>> # Node ID 7c48c97a07b865c86a75562f94656a64a8506273
>> # Parent  564ae7d2ec9bee86b00a6ba817271ac0b19deca7
>> revset: introduce optional 'while' predicate for ancestors()
>>
>> When specifying a 'while' set, ancestors() will now only visit 
>> parents that are
>> in that set. This makes it possible to prune while doing an ancestor 
>> traversal
>> and reduce the number of membership tests.  Such a pruning is very 
>> convenient
>> when expensive checks are involved.
>>
>> The primary initial use case for this feature is that filtering on 
>> branch name
>> is so expensive. Often it is just as relevant to prune everything not 
>> on the
>> branch.
>
> Feature seems interresting. However ther is a massive refactoring on 
> revset in progress. I'll look at the patch after the end of the 
> refactoring landed (opfully tomorrow).

Any news on this ... or general thoughts on it from others?

Do you guys agree such ancestor pruning is relevant? Can you imagine 
other kinds of pruning than when yielding ancestors?

Some related queries could be max(::.&branch(default)) or 
min(.::&branch(stable)), but I assume the optimizer should be able to 
figure out it has iterate in the right order and 'prune' after finding 
the first match.

Expressions with heads() and roots() are more tricky to optimize 
optimatically but should also be possible without special syntax / 
function parameters.

/Mads