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"""Transfers data from AWS Redshift into a S3 Bucket."""
from typing import TYPE_CHECKING, Iterable, List, Mapping, Optional, Sequence, Union
from airflow.models import BaseOperator
from airflow.providers.amazon.aws.hooks.redshift_sql import RedshiftSQLHook
from airflow.providers.amazon.aws.hooks.s3 import S3Hook
from airflow.providers.amazon.aws.utils.redshift import build_credentials_block
if TYPE_CHECKING:
from airflow.utils.context import Context
[docs]class RedshiftToS3Operator(BaseOperator):
"""
Executes an UNLOAD command to s3 as a CSV with headers
.. seealso::
For more information on how to use this operator, take a look at the guide:
:ref:`howto/operator:RedshiftToS3Operator`
:param s3_bucket: reference to a specific S3 bucket
:param s3_key: reference to a specific S3 key. If ``table_as_file_name`` is set
to False, this param must include the desired file name
:param schema: reference to a specific schema in redshift database
Applicable when ``table`` param provided.
:param table: reference to a specific table in redshift database
Used when ``select_query`` param not provided.
:param select_query: custom select query to fetch data from redshift database
:param redshift_conn_id: reference to a specific redshift database
:param aws_conn_id: reference to a specific S3 connection
If the AWS connection contains 'aws_iam_role' in ``extras``
the operator will use AWS STS credentials with a token
https://docs.aws.amazon.com/redshift/latest/dg/copy-parameters-authorization.html#copy-credentials
:param verify: Whether or not to verify SSL certificates for S3 connection.
By default SSL certificates are verified.
You can provide the following values:
- ``False``: do not validate SSL certificates. SSL will still be used
(unless use_ssl is False), but SSL certificates will not be
verified.
- ``path/to/cert/bundle.pem``: A filename of the CA cert bundle to uses.
You can specify this argument if you want to use a different
CA cert bundle than the one used by botocore.
:param unload_options: reference to a list of UNLOAD options
:param autocommit: If set to True it will automatically commit the UNLOAD statement.
Otherwise it will be committed right before the redshift connection gets closed.
:param include_header: If set to True the s3 file contains the header columns.
:param parameters: (optional) the parameters to render the SQL query with.
:param table_as_file_name: If set to True, the s3 file will be named as the table.
Applicable when ``table`` param provided.
"""
[docs] template_fields: Sequence[str] = (
's3_bucket',
's3_key',
'schema',
'table',
'unload_options',
'select_query',
)
[docs] template_ext: Sequence[str] = ('.sql',)
[docs] template_fields_renderers = {'select_query': 'sql'}
def __init__(
self,
*,
s3_bucket: str,
s3_key: str,
schema: Optional[str] = None,
table: Optional[str] = None,
select_query: Optional[str] = None,
redshift_conn_id: str = 'redshift_default',
aws_conn_id: str = 'aws_default',
verify: Optional[Union[bool, str]] = None,
unload_options: Optional[List] = None,
autocommit: bool = False,
include_header: bool = False,
parameters: Optional[Union[Mapping, Iterable]] = None,
table_as_file_name: bool = True, # Set to True by default for not breaking current workflows
**kwargs,
) -> None:
super().__init__(**kwargs)
self.s3_bucket = s3_bucket
self.s3_key = f'{s3_key}/{table}_' if (table and table_as_file_name) else s3_key
self.schema = schema
self.table = table
self.redshift_conn_id = redshift_conn_id
self.aws_conn_id = aws_conn_id
self.verify = verify
self.unload_options = unload_options or [] # type: List
self.autocommit = autocommit
self.include_header = include_header
self.parameters = parameters
self.table_as_file_name = table_as_file_name
if select_query:
self.select_query = select_query
elif self.schema and self.table:
self.select_query = f"SELECT * FROM {self.schema}.{self.table}"
else:
raise ValueError(
'Please provide both `schema` and `table` params or `select_query` to fetch the data.'
)
if self.include_header and 'HEADER' not in [uo.upper().strip() for uo in self.unload_options]:
self.unload_options = list(self.unload_options) + [
'HEADER',
]
def _build_unload_query(
self, credentials_block: str, select_query: str, s3_key: str, unload_options: str
) -> str:
return f"""
UNLOAD ('{select_query}')
TO 's3://{self.s3_bucket}/{s3_key}'
credentials
'{credentials_block}'
{unload_options};
"""
[docs] def execute(self, context: 'Context') -> None:
redshift_hook = RedshiftSQLHook(redshift_conn_id=self.redshift_conn_id)
conn = S3Hook.get_connection(conn_id=self.aws_conn_id)
if conn.extra_dejson.get('role_arn', False):
credentials_block = f"aws_iam_role={conn.extra_dejson['role_arn']}"
else:
s3_hook = S3Hook(aws_conn_id=self.aws_conn_id, verify=self.verify)
credentials = s3_hook.get_credentials()
credentials_block = build_credentials_block(credentials)
unload_options = '\n\t\t\t'.join(self.unload_options)
unload_query = self._build_unload_query(
credentials_block, self.select_query, self.s3_key, unload_options
)
self.log.info('Executing UNLOAD command...')
redshift_hook.run(unload_query, self.autocommit, parameters=self.parameters)
self.log.info("UNLOAD command complete...")
