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from airflow.hooks.postgres_hook import PostgresHook
from airflow.hooks.S3_hook import S3Hook
from airflow.models import BaseOperator
from airflow.utils.decorators import apply_defaults
[docs]class RedshiftToS3Transfer(BaseOperator):
"""
Executes an UNLOAD command to s3 as a CSV with headers
:param schema: reference to a specific schema in redshift database
:type schema: str
:param table: reference to a specific table in redshift database
:type table: str
:param s3_bucket: reference to a specific S3 bucket
:type s3_bucket: str
:param s3_key: reference to a specific S3 key
:type s3_key: str
:param redshift_conn_id: reference to a specific redshift database
:type redshift_conn_id: str
:param aws_conn_id: reference to a specific S3 connection
:type aws_conn_id: str
: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.
:type verify: bool or str
:param unload_options: reference to a list of UNLOAD options
:type unload_options: list
"""
@apply_defaults
def __init__(
self,
schema,
table,
s3_bucket,
s3_key,
redshift_conn_id='redshift_default',
aws_conn_id='aws_default',
verify=None,
unload_options=tuple(),
autocommit=False,
include_header=False,
*args, **kwargs):
super(RedshiftToS3Transfer, self).__init__(*args, **kwargs)
self.schema = schema
self.table = table
self.s3_bucket = s3_bucket
self.s3_key = s3_key
self.redshift_conn_id = redshift_conn_id
self.aws_conn_id = aws_conn_id
self.verify = verify
self.unload_options = unload_options
self.autocommit = autocommit
self.include_header = include_header
if self.include_header and \
'PARALLEL OFF' not in [uo.upper().strip() for uo in unload_options]:
self.unload_options = list(unload_options) + ['PARALLEL OFF', ]
[docs] def execute(self, context):
self.hook = PostgresHook(postgres_conn_id=self.redshift_conn_id)
self.s3 = S3Hook(aws_conn_id=self.aws_conn_id, verify=self.verify)
credentials = self.s3.get_credentials()
unload_options = '\n\t\t\t'.join(self.unload_options)
if self.include_header:
self.log.info("Retrieving headers from %s.%s...",
self.schema, self.table)
columns_query = """SELECT column_name
FROM information_schema.columns
WHERE table_schema = '{schema}'
AND table_name = '{table}'
ORDER BY ordinal_position
""".format(schema=self.schema,
table=self.table)
cursor = self.hook.get_conn().cursor()
cursor.execute(columns_query)
rows = cursor.fetchall()
columns = [row[0] for row in rows]
column_names = ', '.join("{0}".format(c) for c in columns)
column_headers = ', '.join("\\'{0}\\'".format(c) for c in columns)
column_castings = ', '.join("CAST({0} AS text) AS {0}".format(c)
for c in columns)
select_query = """SELECT {column_names} FROM
(SELECT 2 sort_order, {column_castings}
FROM {schema}.{table}
UNION ALL
SELECT 1 sort_order, {column_headers})
ORDER BY sort_order"""\
.format(column_names=column_names,
column_castings=column_castings,
column_headers=column_headers,
schema=self.schema,
table=self.table)
else:
select_query = "SELECT * FROM {schema}.{table}"\
.format(schema=self.schema,
table=self.table)
unload_query = """
UNLOAD ('{select_query}')
TO 's3://{s3_bucket}/{s3_key}/{table}_'
with credentials
'aws_access_key_id={access_key};aws_secret_access_key={secret_key}'
{unload_options};
""".format(select_query=select_query,
table=self.table,
s3_bucket=self.s3_bucket,
s3_key=self.s3_key,
access_key=credentials.access_key,
secret_key=credentials.secret_key,
unload_options=unload_options)
self.log.info('Executing UNLOAD command...')
self.hook.run(unload_query, self.autocommit)
self.log.info("UNLOAD command complete...")