RewriteJoins

The immutable state of the phase that can also be accessed by other phases.

Run the phase

Recursively push refs from the right-hand side of a Join to the left-hand side out of the join. This is only possible when they occur in a a mapping Bind(_, _, Pure(StructNode)) directly at the RHS of a Join. Returns the (possibly transformed) Join and replacements for forward paths into it.

TODO: If the remainder of the mapping Bind is purely aliasing, eliminate it entirely.

Merge nested mapping operations of the form Bind(_, Bind(_, _, Pure(StructNode(p1), _)), Pure(StructNode(p2), _)) into a single Bind, provided that each element of either p1 or p2 contains not more than one path. This transformation is not required for the correctness of join rewriting but it keeps the tree smaller to speed up subsequent phases.

Recursively hoist Filter out of of Bind(_, Filter, Pure(StructNode)). Returns the possibly modified tree plus a set of invalidated TypeSymbols (non-empty if additional columns have to be added to the base projection for the filters).

Hoist Filter nodes in Join generators into join predicates.

In a Join(s1, _, _, Join(_, _, _, _, JoinType.Inner, on2), JoinType.Inner, on1) where parts of on2 refer to s1, merge them into on1. Nested joins are processed recursively. The same is done in the opposite direction, pushing predicates down into sub-joins if they only reference one side of the join.

Returns a string representation of the object.

The default representation is platform dependent.

The unique name of the phase