joinKeys

DataFrame joinKeys(DataFrame left,  DataFrame right,  string[]  leftOn,
       string[]  rightOn,  JoinKind kind =  JoinKind.INNER,
       string suffix =  "_right")

The multi-column join (ADR-2026-10-30-03): a row matches only when every key pair holds under the existing per-kind rules; any null component never matches (LEFT keeps the row null-padded, SEMI drops it, ANTI keeps it - the single-key doctrine componentwise). OUTER coalesces every paired key column. Emission stays left-order with right-row order within a left row and the deterministic unmatched-right tail.

Parameters

`left`	the left frame
`right`	the right frame
`leftOn`	the left key column names
`rightOn`	the right key column names (same length)
`kind`	the join kind
`suffix`	the collision suffix for non-key right columns

Returns

the joined frame.

Throws

DataFrameException on missing columns, length-mismatched

key arrays, empty keys, dtype/kind violations per pair.