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from airflow.contrib.hooks.bigquery_hook import BigQueryHook
from airflow.models import BaseOperator
from airflow.utils.decorators import apply_defaults


class BigQueryToBigQueryOperator(BaseOperator):
    """
    Copies data from one BigQuery table to another.

    .. seealso::
        For more details about these parameters:
        https://cloud.google.com/bigquery/docs/reference/v2/jobs#configuration.copy

    :param source_project_dataset_tables: One or more
        dotted ``(project:|project.)<dataset>.<table>`` BigQuery tables to use as the
        source data. If ``<project>`` is not included, project will be the
        project defined in the connection json. Use a list if there are multiple
        source tables. (templated)
    :type source_project_dataset_tables: list|string
    :param destination_project_dataset_table: The destination BigQuery
        table. Format is: ``(project:|project.)<dataset>.<table>`` (templated)
    :type destination_project_dataset_table: str
    :param write_disposition: The write disposition if the table already exists.
    :type write_disposition: str
    :param create_disposition: The create disposition if the table doesn't exist.
    :type create_disposition: str
    :param bigquery_conn_id: reference to a specific BigQuery hook.
    :type bigquery_conn_id: str
    :param delegate_to: The account to impersonate, if any.
        For this to work, the service account making the request must have domain-wide
        delegation enabled.
    :type delegate_to: str
    :param labels: a dictionary containing labels for the job/query,
        passed to BigQuery
    :type labels: dict
    """
    template_fields = ('source_project_dataset_tables',
                       'destination_project_dataset_table', 'labels')
    template_ext = ('.sql',)
    ui_color = '#e6f0e4'

    @apply_defaults
    def __init__(self,
                 source_project_dataset_tables,
                 destination_project_dataset_table,
                 write_disposition='WRITE_EMPTY',
                 create_disposition='CREATE_IF_NEEDED',
                 bigquery_conn_id='bigquery_default',
                 delegate_to=None,
                 labels=None,
                 *args,
                 **kwargs):
        super(BigQueryToBigQueryOperator, self).__init__(*args, **kwargs)
        self.source_project_dataset_tables = source_project_dataset_tables
        self.destination_project_dataset_table = destination_project_dataset_table
        self.write_disposition = write_disposition
        self.create_disposition = create_disposition
        self.bigquery_conn_id = bigquery_conn_id
        self.delegate_to = delegate_to
        self.labels = labels

    def execute(self, context):
        self.log.info(
            'Executing copy of %s into: %s',
            self.source_project_dataset_tables, self.destination_project_dataset_table
        )
        hook = BigQueryHook(bigquery_conn_id=self.bigquery_conn_id,
                            delegate_to=self.delegate_to)
        conn = hook.get_conn()
        cursor = conn.cursor()
        cursor.run_copy(
            self.source_project_dataset_tables,
            self.destination_project_dataset_table,
            self.write_disposition,
            self.create_disposition,
            self.labels)
