# -*- coding: utf-8 -*-
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# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
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#
# http://www.apache.org/licenses/LICENSE-2.0
#
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from builtins import str
from pyhive import presto
from pyhive.exc import DatabaseError
from airflow.hooks.dbapi_hook import DbApiHook
class PrestoException(Exception):
pass
[docs]class PrestoHook(DbApiHook):
"""
Interact with Presto through PyHive!
>>> ph = PrestoHook()
>>> sql = "SELECT count(1) AS num FROM airflow.static_babynames"
>>> ph.get_records(sql)
[[340698]]
"""
conn_name_attr = 'presto_conn_id'
default_conn_name = 'presto_default'
[docs] def get_conn(self):
"""Returns a connection object"""
db = self.get_connection(self.presto_conn_id)
return presto.connect(
host=db.host,
port=db.port,
username=db.login,
catalog=db.extra_dejson.get('catalog', 'hive'),
schema=db.schema)
@staticmethod
def _strip_sql(sql):
return sql.strip().rstrip(';')
def _get_pretty_exception_message(self, e):
"""
Parses some DatabaseError to provide a better error message
"""
if (hasattr(e, 'message') and
'errorName' in e.message and
'message' in e.message):
return ('{name}: {message}'.format(
name=e.message['errorName'],
message=e.message['message']))
else:
return str(e)
[docs] def get_records(self, hql, parameters=None):
"""
Get a set of records from Presto
"""
try:
return super(PrestoHook, self).get_records(
self._strip_sql(hql), parameters)
except DatabaseError as e:
raise PrestoException(self._get_pretty_exception_message(e))
[docs] def get_first(self, hql, parameters=None):
"""
Returns only the first row, regardless of how many rows the query
returns.
"""
try:
return super(PrestoHook, self).get_first(
self._strip_sql(hql), parameters)
except DatabaseError as e:
raise PrestoException(self._get_pretty_exception_message(e))
[docs] def get_pandas_df(self, hql, parameters=None):
"""
Get a pandas dataframe from a sql query.
"""
import pandas
cursor = self.get_cursor()
try:
cursor.execute(self._strip_sql(hql), parameters)
data = cursor.fetchall()
except DatabaseError as e:
raise PrestoException(self._get_pretty_exception_message(e))
column_descriptions = cursor.description
if data:
df = pandas.DataFrame(data)
df.columns = [c[0] for c in column_descriptions]
else:
df = pandas.DataFrame()
return df
[docs] def run(self, hql, parameters=None):
"""
Execute the statement against Presto. Can be used to create views.
"""
return super(PrestoHook, self).run(self._strip_sql(hql), parameters)
# TODO Enable commit_every once PyHive supports transaction.
# Unfortunately, PyHive 0.5.1 doesn't support transaction for now,
# whereas Presto 0.132+ does.
[docs] def insert_rows(self, table, rows, target_fields=None):
"""
A generic way to insert a set of tuples into a table.
:param table: Name of the target table
:type table: str
:param rows: The rows to insert into the table
:type rows: iterable of tuples
:param target_fields: The names of the columns to fill in the table
:type target_fields: iterable of strings
"""
super(PrestoHook, self).insert_rows(table, rows, target_fields, 0)