Function split_is_not_distinct_from_and_other_join_predicate 

fn split_is_not_distinct_from_and_other_join_predicate(
    filter: Expr,
    left_schema: &DFSchema,
    right_schema: &DFSchema,
) -> Result<(Vec<(Expr, Expr)>, Option<Expr>)>

See split_eq_and_noneq_join_predicate’s comment for the idea. This function is splitting out is not distinct from expressions instead of equal exprs. The is not distinct from exprs will be return as EquijoinPredicate.

Example

• Input: a.id IS NOT DISTINCT FROM b.id AND a.x > 10 AND b.x > b.id
• Output from this splitter: Ok([a.id, b.id], Some((a.x > 10) AND (b.x > b.id)))

Note

Caller should be cautious – is not distinct from is not equivalent to an equal expression; the caller is responsible for correctly setting the nulls equals nulls property in the join operator (if it supports it) to make the transformation valid.

For the above example: in downstream, a valid plan that uses the extracted equijoin keys should look like:

HashJoin

• on: a.id = b.id (equality)
• join_filter: (a.x > 10) AND (b.x > b.id)
• nulls_equals_null: true

This reflects that IS NOT DISTINCT FROM treats NULL = NULL as true and thus requires setting NullEquality::NullEqualsNull in the join operator to preserve semantics while enabling an equi-join implementation (e.g., HashJoin).