Category Archives: Databases Administration

Covering NoSQL, Relational Database, Data Visualization, and Reporting.

Quick Start To Using MongoDB with Python on Linux

With it’s rapid growth in popularity MongoDB is quickly becoming one of the top NoSQL Databases out there and with Python being one of the top ten programming languages according to Tiobe Software’s Programming Community Index. I’ve decided to write a quick how-to to show you just how easy it is to get started with MongoDB and Python.

 

Assuming that you all ready have Python installed on your system. We’ll start with downloading and installing MongoDB. The first that you will need to do is download the appropriate package from http://www.mongodb.org/downloads to your /tmp directory.

 

$ curl http://fastdl.mongodb.org/linux/mongodb-linux-i686-1.6.3.tgz > /tmp/mongo.tgz

 

Once you have downloaded the correct package, find a suitable directory to unpack it and move it to, such as /opt/mongodb.

 

$ cd /tmp

$ tar -zxf mongo.tgz

$ sudo mv mongodb-linux-i686-1.6.3 /opt/mongodb

 

Now you will need to create the data directory. By default, MongoDB stores it’s data in “/data/db”, but if for some reason you need to change the location of the data directory you will need to use the “–dbpath” option when starting the server. However I am sticking with the default directory.

 

$ sudo mkdir -p /data/db

$ sudo chown -R owerid /data/db

 

You can start MongoDB with the following command.

 

$ /opt/mongodb/bin/mongod

 

Now, test it out by using the MongoDB shell to connect to the server as follows.

 

$ /opt/mongodb/bin/mongo

MongoDB shell version: 1.6.3

connecting to: test

> db.foo.save( { Message : “Hello World” } )

> db.foo.find()

{ “_id” : ObjectId(“4cdd92bc4f6fb75dd2a7642d”), “Message” : “Hello World” }

>

 

Once you have verified that MongoDB is working you will need to download the Python driver for it which are called “PyMongo”. If you have the Python “setuptools” installed you should be able to do “easy_install pymongo” to install the drivers. Otherwise you can download the project source from http://pypi.python.org/pypi/pymongo/ to install the MongoDB drivers.

 

$ curl http://pypi.python.org/packages/source/p/pymongo/pymongo-1.9.tar.gz  > /tmp/pymongo-1.9.tar.gz

$ tar -zxf pymongo-1.9.tar.gz

$ cd pymongo-1.9/

$ python setup.py install

 

After everything is installed it’s time to test it all out, so just pop open your favor Python IDE or the Python Console and give it a go. Here is a simple example.

 

$ python

Python 2.4.3 (#1, Nov 11 2010, 13:34:43)

[GCC 4.1.2 20080704 (Red Hat 4.1.2-48)] on linux2

Type “help”, “copyright”, “credits” or “license” for more information.

>>> import pymongo

>>> connection = pymongo.Connection( “localhost”, 27017 )

>>> db = connection.test

>>> db.foo.save({ “Message” : “Hello World 2” })

ObjectId(‘4cdd95bfe1382330b5000000′)

>>> for message in db.foo.find():

… print message

…

{u’Message’: u’Hello World’, u’_id’: ObjectId(‘4cdd92bc4f6fb75dd2a7642d’)}

{u’Message’: u’Hello World 2′, u’_id’: ObjectId(‘4cdd95bfe1382330b5000000’)}

>>>

$

 

For more information on the PyMongo check out the website athttp://api.mongodb.org/python/1.9%2B/index.html.

 

Connecting Python to Oracle.

In the current world of heterogeneous networks it seems that you need to be able to connect to ever type of database system out there. In a recent project, I was asked, to take an existing MySQL and Python system and get it to connect to an existing Oracle Data Warehouse system. To be honest, I hadn’t actually ever connected Python to an Oracle Database before and from experience this would be either very painful or pretty straight forward.

Of course like everything Python it was pretty straight forward. The first thing you will need to get is the correct cx_Oracle module from http://cx-oracle.sourceforge.net/. The cx_Oracle module allows you to connect to Oracle databases and it conforms to the Python database API specification. Which makes life easier for everyone. After you have installed the module the rest is just a matter having the right permission to connect to the Oracle Database and writing the code.

Here is quick script showing you how to connect to Oracle with Python.

#!/usr/bin/python

import cx_Oracle

connstr=’scott/tiger’
conn = cx_Oracle.connect(connstr)
curs = conn.cursor()
curs.arraysize=50
curs.execute(‘select 2+2 “aaa” ,3*3 from dual’)
print curs.description
print curs.fetchone()
conn.close()

For more information check out the Python Programming Language – Official Website

Calculating The Percentage of Max Connections in with MySQL 5.1.9 and higher

For longest time it had bugged me that there wasn’t an easy way to put “SHOW STATUS”, “SHOW VARIABLES”, or “SHOW PROCESSLIST” variables into queries, so I could easily calculate stuff like max connections percentage. Then MySQL 5.1.9 came out and you could final start to do SELECT statements on information_schema.GLOBAL_STATUS, information_schema.SESSION_STATUS, information_schema.GLOBAL_VARIABLES, information_schema.SESSION_VARIABLES and information_schema.PROCESSLIST.

The STATUS and VARIABLES tables have basically two columns VARIABLE_NAME and VARIABLE_VALUE. These correspond with the “SHOW STATUS” and “SHOW VARIABLES” command’s Variable_name and Value. The PROCESSLIST table has all the same columns as the “SHOW PROCESSLIST” command.

So now with that being said here is a quick little query that returns the Max Connection Limit, Connection Count, and Connect Percentage of max allowed connections.

/* requires MySQL 5.1.19 or higher */

SELECT v.VARIABLE_VALUE as “Max Connections”,
s.processcount as “Connection Count”,
((s.processcount/v.VARIABLE_VALUE)*100) as “% of max connections allowed”
FROM information_schema.GLOBAL_VARIABLES v,
(SELECT (@proc_connect:=count(*)) processcount FROM information_schema.PROCESSLIST) s
WHERE v.VARIABLE_NAME = ‘max_connections’;

 

MySQL Functions for Converting IP Address to an Integer and Back Again

So after my MySQL server-id idea. I was asked to come up with a function to Convert IP Address. So here it is.

use test;
DROP FUNCTION IF EXISTS IpToInteger;
DELIMITER //
CREATE FUNCTION IpToInteger ( ipAddress CHAR(15) )
RETURNS INT UNSIGNED
DETERMINISTIC
BEGIN
DECLARE o1,o2,o3,o4 char(3);
DECLARE IpInteger INT UNSIGNED;
SET o1 = REPLACE(SUBSTRING(SUBSTRING_INDEX( ipAddress, ‘.’, 1), LENGTH(SUBSTRING_INDEX( ipAddress, ‘.’, 1 – 1) ) + 1), ‘.’, ” );
SET o2 = REPLACE(SUBSTRING(SUBSTRING_INDEX( ipAddress, ‘.’, 2), LENGTH(SUBSTRING_INDEX( ipAddress, ‘.’, 2 – 1) ) + 1), ‘.’, ” );
SET o3 = REPLACE(SUBSTRING(SUBSTRING_INDEX( ipAddress, ‘.’, 3), LENGTH(SUBSTRING_INDEX( ipAddress, ‘.’, 3 – 1) ) + 1), ‘.’, ” );
SET o4 = REPLACE(SUBSTRING(SUBSTRING_INDEX( ipAddress, ‘.’, 4), LENGTH(SUBSTRING_INDEX( ipAddress, ‘.’, 4 – 1) ) + 1), ‘.’, ” );
SELECT ( o1 << 24 ) + ( o2 << 16 ) + ( o3 << 8 ) + o4 INTO IpInteger;
RETURN IpInteger;
END//
DELIMITER ;

use test;
DROP FUNCTION IF EXISTS IntegerToIp;
DELIMITER //
CREATE FUNCTION IntegerToIp( ipInteger INT UNSIGNED )
RETURNS CHAR(16) DETERMINISTIC
BEGIN
DECLARE o1,o2,o3,o4 INT UNSIGNED;
SET o1 = ( ipInteger >> 24 );
SET o2 = ( ipInteger >> 16 << 16 )-( ipInteger >> 24 << 24) >> 16;
SET o3 = (ipInteger >> 8 << 8 ) – ( ipInteger >> 16 << 16 ) >> 8;
SET o4 = ipInteger – ( ipInteger >> 8 << 8 );
RETURN CONCAT( o1, “.” , o2, “.” , o3, “.”, o4 );
END//
DELIMITER ;

mysql> SELECT IpToInteger ( '10.8.208.30' ); +-------------------------------+ | IpToInteger ( '10.8.208.30' ) | +-------------------------------+ | 168349726 | +-------------------------------+ 1 row in set (0.00 sec) mysql> SELECT IntegerToIp( 168349726 ); +--------------------------+ | IntegerToIp( 168349726 ) | +--------------------------+ | 10.8.208.30 | +--------------------------+ 1 row in set (0.00 sec) mysql>