PushPredicateThroughJoin is a base logical optimization that FIXME.
PushPredicateThroughJoin is part of the Operator Optimization before Inferring Filters fixed-point batch in the standard batches of the Catalyst Optimizer.
PushPredicateThroughJoin is simply a Catalyst rule for transforming logical plans, i.e. Rule[LogicalPlan].
// FIXME Demo
apply(plan: LogicalPlan): LogicalPlan