DataFrame.joinAsof

DataFrame joinAsof(DataFrame other,  string leftOn,  string rightOn,
          AsofDirection direction =  AsofDirection.BACKWARD,
          long  tolerance =  long.max)

The sorted asof join (ADR-2026-10-30-03): for each left row, at most one right row - BACKWARD the last with rightKey <= leftKey, FORWARD the first with `>=`, NEAREST the smaller distance (exact ties toward BACKWARD). Both sides must already be sorted ascending by the key (validated, never silently sorted); the tolerance is inclusive, unbounded by default.

Parameters

`other`	the right frame
`leftOn`	the left key column
`rightOn`	the right key column
`direction`	the match direction
`tolerance`	the inclusive maximum distance (key units)

Returns

every left row with its matched right columns.

Throws

DataFrameException on missing columns, kind

violations, unsorted input or a negative tolerance.

DataFrame joinAsof(DataFrame other,  string on,
          AsofDirection direction =  AsofDirection.BACKWARD,
          long  tolerance =  long.max)

Ditto, the same key name on both sides.