Refactor PredicateBuilder from singleton to instance

[mrgilman]

No description provided.

[rafaelfranca]

Thanks! What is the reason for this change?

[rafaelfranca]

In fact this is reverting a change @tenderlove made some time ago to avoid instantiating objects 83633b8

[sgrif]

I had asked her to work on this, it's part of the larger refactoring to remove type casting from Arel. One of the things we need to do in order to make that easier is remove the duplication inside of the ArrayHandler with regards to ranges and single value equality. The easiest path to do that is to pass the predicate builder into the handler, but for that to work we need a single method we can call with reasonable parameters.

[sgrif]

We can probably reduce this down to a single allocation per AR class later to keep the work of 83633b8

[rafaelfranca]

👍, just wondering what was the reason. The code seems good to me.