Function validate_join_condition

python/pathway/internals/joins.py:1137–1168

(
    cond: expr.ColumnExpression, left: Table, right: Table
)

def validate_join_condition(
    cond: expr.ColumnExpression, left: Table, right: Table
) -> tuple[expr.ColumnReference, expr.ColumnReference, expr.ColumnBinaryOpExpression]:
    cond = validate_shape(cond)
    try:
        eval_type(cond)
    except TypeError:
        raise TypeError(
            "Incompatible types in a join condition.\n"
            + f"The types are: {eval_type(cond._left)} and {eval_type(cond._right)}. "
            + "You might try casting the respective columns to Any type to circumvent this,"
            + " but this is most probably an error."
        )
    cond_left = cast(expr.ColumnReference, cond._left)
    cond_right = cast(expr.ColumnReference, cond._right)
    if cond_left.table == right and cond_right.table == left:
        raise ValueError(
            "The boolean condition is not properly ordered.\n"
            + "The left part should refer to left joinable and the right one should refer to the right joinable,"
            + " e.g. t1.join(t2, t1.bar==t2.foo)."
        )
    if cond_left.table != left:
        raise ValueError(
            "Left part of a join condition has to be a reference to a table "
            + "on the left side of a join"
        )
    if cond_right.table != right:
        raise ValueError(
            "Right part of a join condition has to be a reference to a table "
            + "on the right side of a join"
        )
    return cond_left, cond_right, cond


def join(