Major Description
BindReferences contains a n^2 loop which causes performance issues when operating over large schemas: to determine the ordinal of an input, we perform a linear scan over the input array. Because input can sometimes be a List, the call to input(ordinal).nullable can also be O( n ).
Instead of performing a linear scan, we can convert the input into an array and build a hash map to map from expression ids to ordinals. The greater up-front cost of the map construction is offset by the fact that an expression can contain multiple attribute references, so the cost of the map construction is amortized across a number of lookups.
