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import os
import psycopg2
import psycopg2.extensions
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}``.
Note: For Redshift, use keepalives_idle in the extra connection parameters
and set it to less than 300 seconds.
"""
conn_name_attr = 'postgres_conn_id'
default_conn_name = 'postgres_default'
supports_autocommit = True
def __init__(self, *args, **kwargs):
super(PostgresHook, self).__init__(*args, **kwargs)
self.schema = kwargs.pop("schema", None)
[docs] def get_conn(self):
conn = self.get_connection(self.postgres_conn_id)
conn_args = dict(
host=conn.host,
user=conn.login,
password=conn.password,
dbname=self.schema or conn.schema,
port=conn.port)
# 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
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