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#!/usr/bin/env python
#
# Copyright 2009 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""A lightweight wrapper around MySQLdb."""
import copy
import MySQLdb.constants
import MySQLdb.converters
import MySQLdb.cursors
import itertools
import logging
class Connection(object):
"""A lightweight wrapper around MySQLdb DB-API connections.
The main value we provide is wrapping rows in a dict/object so that
columns can be accessed by name. Typical usage:
db = database.Connection("localhost", "mydatabase")
for article in db.query("SELECT * FROM articles"):
print article.title
Cursors are hidden by the implementation, but other than that, the methods
are very similar to the DB-API.
We explicitly set the timezone to UTC and the character encoding to
UTF-8 on all connections to avoid time zone and encoding errors.
"""
def __init__(self, host, database, user=None, password=None):
self.host = host
self.database = database
args = dict(conv=CONVERSIONS, use_unicode=True, charset="utf8",
db=database, init_command='SET time_zone = "+0:00"',
sql_mode="TRADITIONAL")
if user is not None:
args["user"] = user
if password is not None:
args["passwd"] = password
# We accept a path to a MySQL socket file or a host(:port) string
if "/" in host:
args["unix_socket"] = host
else:
self.socket = None
pair = host.split(":")
if len(pair) == 2:
args["host"] = pair[0]
args["port"] = int(pair[1])
else:
args["host"] = host
args["port"] = 3306
self._db = None
self._db_args = args
try:
self.reconnect()
except:
logging.error("Cannot connect to MySQL on %s", self.host,
exc_info=True)
def __del__(self):
self.close()
def close(self):
"""Closes this database connection."""
if getattr(self, "_db", None) is not None:
self._db.close()
self._db = None
def reconnect(self):
"""Closes the existing database connection and re-opens it."""
self.close()
self._db = MySQLdb.connect(**self._db_args)
self._db.autocommit(True)
def iter(self, query, *parameters):
"""Returns an iterator for the given query and parameters."""
if self._db is None: self.reconnect()
cursor = MySQLdb.cursors.SSCursor(self._db)
try:
self._execute(cursor, query, parameters)
column_names = [d[0] for d in cursor.description]
for row in cursor:
yield Row(zip(column_names, row))
finally:
cursor.close()
def query(self, query, *parameters):
"""Returns a row list for the given query and parameters."""
cursor = self._cursor()
try:
self._execute(cursor, query, parameters)
column_names = [d[0] for d in cursor.description]
return [Row(itertools.izip(column_names, row)) for row in cursor]
finally:
cursor.close()
def get(self, query, *parameters):
"""Returns the first row returned for the given query."""
rows = self.query(query, *parameters)
if not rows:
return None
elif len(rows) > 1:
raise Exception("Multiple rows returned for Database.get() query")
else:
return rows[0]
def execute(self, query, *parameters):
"""Executes the given query, returning the lastrowid from the query."""
cursor = self._cursor()
try:
self._execute(cursor, query, parameters)
return cursor.lastrowid
finally:
cursor.close()
def executemany(self, query, parameters):
"""Executes the given query against all the given param sequences.
We return the lastrowid from the query.
"""
cursor = self._cursor()
try:
cursor.executemany(query, parameters)
return cursor.lastrowid
finally:
cursor.close()
def _cursor(self):
if self._db is None: self.reconnect()
return self._db.cursor()
def _execute(self, cursor, query, parameters):
try:
return cursor.execute(query, parameters)
except OperationalError:
logging.error("Error connecting to MySQL on %s", self.host)
self.close()
raise
class Row(dict):
"""A dict that allows for object-like property access syntax."""
def __getattr__(self, name):
try:
return self[name]
except KeyError:
raise AttributeError(name)
# Fix the access conversions to properly recognize unicode/binary
FIELD_TYPE = MySQLdb.constants.FIELD_TYPE
FLAG = MySQLdb.constants.FLAG
CONVERSIONS = copy.deepcopy(MySQLdb.converters.conversions)
field_types = [FIELD_TYPE.BLOB, FIELD_TYPE.STRING, FIELD_TYPE.VAR_STRING]
if 'VARCHAR' in vars(FIELD_TYPE):
field_types.append(FIELD_TYPE.VARCHAR)
for field_type in field_types:
CONVERSIONS[field_type].insert(0, (FLAG.BINARY, str))
# Alias some common MySQL exceptions
IntegrityError = MySQLdb.IntegrityError
OperationalError = MySQLdb.OperationalError
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