joinAsofFrames

DataFrame joinAsofFrames(DataFrame left,  DataFrame right,
       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 (in order, at most one right row), BACKWARD takes the last right row with rightKey <= leftKey, FORWARD the first with `>=`, NEAREST the smaller distance with exact ties toward BACKWARD. Duplicate right keys at the chosen position: BACKWARD the last duplicate, FORWARD the first. Tolerance is inclusive (|leftKey - matchKey| <= tolerance, key units); the default is unbounded. Both sides must already be sorted ascending by the key (non-decreasing over the valid values) - validated, never sorted silently. Left null keys stay null-padded; right null rows never match. The key dtypes must be the same ordered kind (the temporal kinds and the numerics).

Parameters

`left`	the left frame
`right`	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 (nulls

where unmatched).

Throws

DataFrameException on missing columns, kind violations,

unsorted input or an out-of-range tolerance.