Function join_outer

python/pathway/internals/joins.py:1482–1566

Outer-joins two tables or join results. Args: self: the left side of the join, ``Table`` or ``JoinResult``. other: the right side of the join, ``Table`` or ``JoinResult``. *on: Columns to join, syntax `self.col1 == other.col2` id: optional id column of the resu

(
    left: Joinable,
    right: Joinable,
    *on: expr.ColumnExpression,
    id: expr.ColumnReference | None = None,
    left_instance: expr.ColumnReference | None = None,
    right_instance: expr.ColumnReference | None = None,
    left_exactly_once: bool = False,
    right_exactly_once: bool = False,
)

def join_outer(
    left: Joinable,
    right: Joinable,
    *on: expr.ColumnExpression,
    id: expr.ColumnReference | None = None,
    left_instance: expr.ColumnReference | None = None,
    right_instance: expr.ColumnReference | None = None,
    left_exactly_once: bool = False,
    right_exactly_once: bool = False,
) -> JoinResult:
    """Outer-joins two tables or join results.

    Args:
        self:  the left side of the join, ``Table`` or ``JoinResult``.
        other:  the right side of the join, ``Table`` or ``JoinResult``.
        *on: Columns to join, syntax `self.col1 == other.col2`
        id: optional id column of the result
        left_instance/right_instance: optional arguments describing partitioning of the data into separate
            instances
        left_exactly_once: if you can guarantee that each row on the left side of the join will be
            joined at most once, then you can set this parameter to ``True``. Then each row after
            getting a match is removed from the join state. As a result, less memory is needed.
            Works only for append-only tables.
        right_exactly_once: if you can guarantee that each row on the right side of the join will be
            joined at most once, then you can set this parameter to ``True``. Then each row after
            getting a match is removed from the join state. As a result, less memory is needed.
            Works only for append-only tables.

    Remarks: args cannot contain id column from either of tables, \
        as the result table has id column with auto-generated ids; \
        it can be selected by assigning it to a column with defined \
        name (passed in kwargs)

    Behavior:
    - for rows from the left side that were not matched with the right side,
    missing values on the right are replaced with `None`
    - for rows from the right side that were not matched with the left side,
    missing values on the left are replaced with `None`
    - for rows that were matched the behavior is the same as that of an inner join.

    Returns:
        JoinResult: an object on which `.select()` may be called to extract relevant
        columns from the result of the join.

    Example:

    >>> import pathway as pw
    >>> t1 = pw.debug.table_from_markdown(
    ...     '''
    ...         | a  | b
    ...       1 | 11 | 111
    ...       2 | 12 | 112
    ...       3 | 13 | 113
    ...       4 | 13 | 114
    ...     '''
    ... )
    >>> t2 = pw.debug.table_from_markdown(
    ...     '''