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import os
import psycopg2
import psycopg2.extensions
import psycopg2.extras
from contextlib import closing
from airflow.hooks.dbapi_hook import DbApiHook
[docs]class PostgresHook(DbApiHook):
"""
Interact with Postgres.
You can specify ssl parameters in the extra field of your connection
as ``{"sslmode": "require", "sslcert": "/path/to/cert.pem", etc}``.
Also you can choose cursor as ``{"cursor": "dictcursor"}``. Refer to the
psycopg2.extras for more details.
Note: For Redshift, use keepalives_idle in the extra connection parameters
and set it to less than 300 seconds.
Note: For AWS IAM authentication, use iam in the extra connection parameters
and set it to true. Leave the password field empty. This will use the
"aws_default" connection to get the temporary token unless you override
in extras.
extras example: ``{"iam":true, "aws_conn_id":"my_aws_conn"}``
For Redshift, also use redshift in the extra connection parameters and
set it to true. The cluster-identifier is extracted from the beginning of
the host field, so is optional. It can however be overridden in the extra field.
extras example: ``{"iam":true, "redshift":true, "cluster-identifier": "my_cluster_id"}``
"""
[docs] conn_name_attr = 'postgres_conn_id'
[docs] default_conn_name = 'postgres_default'
[docs] supports_autocommit = True
def __init__(self, *args, **kwargs):
super(PostgresHook, self).__init__(*args, **kwargs)
self.schema = kwargs.pop("schema", None)
[docs] def _get_cursor(self, raw_cursor):
_cursor = raw_cursor.lower()
if _cursor == 'dictcursor':
return psycopg2.extras.DictCursor
if _cursor == 'realdictcursor':
return psycopg2.extras.RealDictCursor
if _cursor == 'namedtuplecursor':
return psycopg2.extras.NamedTupleCursor
raise ValueError('Invalid cursor passed {}'.format(_cursor))
[docs] def get_conn(self):
conn_id = getattr(self, self.conn_name_attr)
conn = self.get_connection(conn_id)
# check for authentication via AWS IAM
if conn.extra_dejson.get('iam', False):
conn.login, conn.password, conn.port = self.get_iam_token(conn)
conn_args = dict(
host=conn.host,
user=conn.login,
password=conn.password,
dbname=self.schema or conn.schema,
port=conn.port)
raw_cursor = conn.extra_dejson.get('cursor', False)
if raw_cursor:
conn_args['cursor_factory'] = self._get_cursor(raw_cursor)
# check for ssl parameters in conn.extra
for arg_name, arg_val in conn.extra_dejson.items():
if arg_name in ['sslmode', 'sslcert', 'sslkey',
'sslrootcert', 'sslcrl', 'application_name',
'keepalives_idle']:
conn_args[arg_name] = arg_val
self.conn = psycopg2.connect(**conn_args)
return self.conn
[docs] def copy_expert(self, sql, filename, open=open):
"""
Executes SQL using psycopg2 copy_expert method.
Necessary to execute COPY command without access to a superuser.
Note: if this method is called with a "COPY FROM" statement and
the specified input file does not exist, it creates an empty
file and no data is loaded, but the operation succeeds.
So if users want to be aware when the input file does not exist,
they have to check its existence by themselves.
"""
if not os.path.isfile(filename):
with open(filename, 'w'):
pass
with open(filename, 'r+') as f:
with closing(self.get_conn()) as conn:
with closing(conn.cursor()) as cur:
cur.copy_expert(sql, f)
f.truncate(f.tell())
conn.commit()
[docs] def bulk_load(self, table, tmp_file):
"""
Loads a tab-delimited file into a database table
"""
self.copy_expert("COPY {table} FROM STDIN".format(table=table), tmp_file)
[docs] def bulk_dump(self, table, tmp_file):
"""
Dumps a database table into a tab-delimited file
"""
self.copy_expert("COPY {table} TO STDOUT".format(table=table), tmp_file)
@staticmethod
[docs] def _serialize_cell(cell, conn):
"""
Postgresql will adapt all arguments to the execute() method internally,
hence we return cell without any conversion.
See http://initd.org/psycopg/docs/advanced.html#adapting-new-types for
more information.
:param cell: The cell to insert into the table
:type cell: object
:param conn: The database connection
:type conn: connection object
:return: The cell
:rtype: object
"""
return cell
[docs] def get_iam_token(self, conn):
"""
Uses AWSHook to retrieve a temporary password to connect to Postgres
or Redshift. Port is required. If none is provided, default is used for
each service
"""
from airflow.contrib.hooks.aws_hook import AwsHook
redshift = conn.extra_dejson.get('redshift', False)
aws_conn_id = conn.extra_dejson.get('aws_conn_id', 'aws_default')
aws_hook = AwsHook(aws_conn_id)
login = conn.login
if conn.port is None:
port = 5439 if redshift else 5432
else:
port = conn.port
if redshift:
# Pull the custer-identifier from the beginning of the Redshift URL
# ex. my-cluster.ccdre4hpd39h.us-east-1.redshift.amazonaws.com returns my-cluster
cluster_identifier = conn.extra_dejson.get('cluster-identifier', conn.host.split('.')[0])
client = aws_hook.get_client_type('redshift')
cluster_creds = client.get_cluster_credentials(
DbUser=conn.login,
DbName=self.schema or conn.schema,
ClusterIdentifier=cluster_identifier,
AutoCreate=False)
token = cluster_creds['DbPassword']
login = cluster_creds['DbUser']
else:
client = aws_hook.get_client_type('rds')
token = client.generate_db_auth_token(conn.host, port, conn.login)
return login, token, port