Row multiplication, unmatched keys and uniqueness violations before a table join

Overview

Takes the join keys of two tables (every row's key, or distinct keys with row counts) and computes the exact output row count of an inner, left, right or full equi-join with SQL NULL semantics, the observed cardinality (one-to-one, one-to-many, many-to-one, many-to-many), the keys that multiply rows the most, unmatched keys on each side and the first duplicate row when a side was assumed unique. It also flags keys that match only after loose coercion (7 vs "7", "007" vs 7, tr

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