Function write_snapshot

python/pathway/io/postgres/__init__.py:897–1051

**WARNING**: This method is deprecated. Please use ``pw.io.postgres.write`` with the parameter ``output_table_type="snapshot"`` instead. Note that the new version does not create the ``time`` and ``diff`` columns and maintains a current snapshot of the table you are writing. Maintai

(
    table: Table,
    postgres_settings: dict,
    table_name: str,
    primary_key: list[str],
    *,
    max_batch_size: int | None = None,
    init_mode: Literal["default", "create_if_not_exists", "replace"] = "default",
    name: str | None = None,
    sort_by: Iterable[ColumnReference] | None = None,
    _external_diff_column: ColumnReference | None = None,
)

@check_arg_types
def write_snapshot(
    table: Table,
    postgres_settings: dict,
    table_name: str,
    primary_key: list[str],
    *,
    max_batch_size: int | None = None,
    init_mode: Literal["default", "create_if_not_exists", "replace"] = "default",
    name: str | None = None,
    sort_by: Iterable[ColumnReference] | None = None,
    _external_diff_column: ColumnReference | None = None,
) -> None:
    """**WARNING**: This method is deprecated. Please use ``pw.io.postgres.write`` with
    the parameter ``output_table_type="snapshot"`` instead. Note that the new version
    does not create the ``time`` and ``diff`` columns and maintains a current snapshot
    of the table you are writing.

    Maintains a snapshot of a table within a Postgres table.

    In order for write to be successful, it is required that the table contains ``time``
    and ``diff`` columns of the integer type.

    Args:
        postgres_settings: Components of the connection string for Postgres.
        table_name: Name of the target table.
        primary_key: Names of the fields which serve as a primary key in the Postgres table.
        max_batch_size: Maximum number of entries allowed to be committed within a
            single transaction.
        init_mode: "default": The default initialization mode;
            "create_if_not_exists": initializes the SQL writer by creating the necessary table
            if they do not already exist;
            "replace": Initializes the SQL writer by replacing any existing table.
        name: A unique name for the connector. If provided, this name will be used in
            logs and monitoring dashboards.
        sort_by: If specified, the output will be sorted in ascending order based on the
            values of the given columns within each minibatch. When multiple columns are provided,
            the corresponding value tuples will be compared lexicographically.

    Returns:
        None

    Example:

    Consider there is a table ``stats`` in the Pathway Live Data Framework, containing the average
    number of requests to some
    service or operation per user, over some period of time. The number of requests
    can be large, so we decide not to store the whole stream of changes, but to only store
    a snapshot of the data, which can be actualized by the Pathway Live Data Framework.

    The minimum set-up would require us to have a Postgres table with two columns: the ID
    of the user ``user_id`` and the number of requests across some period of time ``number_of_requests``.
    In order to maintain consistency, we also need two extra columns: ``time`` and ``diff``.

    The SQL for the creation of such table would look as follows:

    .. code-block:: sql

        CREATE TABLE user_stats (