refactor: UpdateDistinct and Duplicate operations.

[drupol]

This PR:

• Align the Duplicate operation on Distinct
• Update the Distinct operation
  The distinct operation was not designed in a lazy way.
  The previous version was storing in an array each pair of key-value from the iterator. This is not how we should do that.
  The previous version was based on Reduce and was traversing the whole iterator before going to the next operation.
  This is not really optimal and we should update that.
• Has updated documentation and examples
• The Duplicate implementation is ready and I'm happy of it

Because of the nature of these operations and their side effects (the $stack variable), I'm unable to test them completely, especially the continue 2 statement. Infection will most probably detect that without any trouble (Basically, there is no need to go through the whole $seen array once the inner condition is met).
I haven't found a better way to achieve this, maybe the enlightenment will come another day.

[AlexandruGG]

Nice one 👍 .

This would be the kind of refactoring that would really benefit from having PHPBench so we could see the difference in runtime and memory used by the operations.

[drupol]

Nice one +1 .

This would be the kind of refactoring that would really benefit from having PHPBench so we could see the difference in runtime and memory used by the operations.

I definitely agree.

That said, I did the tests locally and the difference is significant!

[AlexandruGG]

Nice one +1 .
This would be the kind of refactoring that would really benefit from having PHPBench so we could see the difference in runtime and memory used by the operations.

I definitely agree.

That said, I did the tests locally and the difference is significant!

I'll find the time at some point to play around with phpbench and see how we introduce it into this project