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The AlloyDB ODBC Driver is a powerful tool that allows you to connect with live data from AlloyDB, directly from any applications that support ODBC connectivity.

Access AlloyDB data like you would a database - read, write, and update AlloyDB 0, etc. through a standard ODBC Driver interface.

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How to Connect to AlloyDB Data in Python on Linux/UNIX


Create Python applications on Linux/UNIX machines with connectivity to AlloyDB data. Leverage the pyodbc module for ODBC in Python.

The rich ecosystem of Python modules lets you get to work quicker and integrate your systems more effectively. With the CData Linux/UNIX ODBC Driver for AlloyDB and the pyodbc module, you can easily build AlloyDB-connected Python applications. This article shows how to use the pyodbc built-in functions to connect to AlloyDB data, execute queries, and output the results.

Using the CData ODBC Drivers on a UNIX/Linux Machine

The CData ODBC Drivers are supported in various Red Hat-based and Debian-based systems, including Ubuntu, Debian, RHEL, CentOS, and Fedora. There are also several libraries and packages that are required, many of which may be installed by default, depending on your system. For more information on the supported versions of Linux operating systems and the required libraries, please refer to the "Getting Started" section in the help documentation (installed and found online).

Installing the Driver Manager

Before installing the driver, check that your system has a driver manager. For this article, you will use unixODBC, a free and open source ODBC driver manager that is widely supported.

For Debian-based systems like Ubuntu, you can install unixODBC with the APT package manager:

$ sudo apt-get install unixodbc unixodbc-dev

For systems based on Red Hat Linux, you can install unixODBC with yum or dnf:

$ sudo yum install unixODBC unixODBC-devel

The unixODBC driver manager reads information about drivers from an odbcinst.ini file and about data sources from an odbc.ini file. You can determine the location of the configuration files on your system by entering the following command into a terminal:

$ odbcinst -j

The output of the command will display the locations of the configuration files for ODBC data sources and registered ODBC drivers. User data sources can only be accessed by the user account whose home folder the odbc.ini is located in. System data sources can be accessed by all users. Below is an example of the output of this command:

DRIVERS............: /etc/odbcinst.ini SYSTEM DATA SOURCES: /etc/odbc.ini FILE DATA SOURCES..: /etc/ODBCDataSources USER DATA SOURCES..: /home/myuser/.odbc.ini SQLULEN Size.......: 8 SQLLEN Size........: 8 SQLSETPOSIROW Size.: 8

Installing the Driver

You can download the driver in standard package formats: the Debian .deb package format or the .rpm file format. Once you have downloaded the file, you can install the driver from the terminal.

The driver installer registers the driver with unixODBC and creates a system DSN, which can be used later in any tools or applications that support ODBC connectivity.

For Debian-based systems like Ubuntu, run the following command with sudo or as root: $ dpkg -i /path/to/package.deb

For Red Hat systems and other systems that support .rpms, run the following command with sudo or as root: $ rpm -i /path/to/package.rpm

Once the driver is installed, you can list the registered drivers and defined data sources using the unixODBC driver manager:

List the Registered Driver(s)

$ odbcinst -q -d CData ODBC Driver for AlloyDB ...

List the Defined Data Source(s)

$ odbcinst -q -s CData AlloyDB Source ...

To use the CData ODBC Driver for AlloyDB with unixODBC, ensure that the driver is configured to use UTF-16. To do so, edit the INI file for the driver (cdata.odbc.alloydb.ini), which can be found in the lib folder in the installation location (typically /opt/cdata/cdata-odbc-driver-for-alloydb), as follows:

cdata.odbc.alloydb.ini

... [Driver] DriverManagerEncoding = UTF-16

Modifying the DSN

The driver installation predefines a system DSN. You can modify the DSN by editing the system data sources file (/etc/odbc.ini) and defining the required connection properties. Additionally, you can create user-specific DSNs that will not require root access to modify in $HOME/.odbc.ini.

The following connection properties are usually required in order to connect to AlloyDB.

  • Server: The host name or IP of the server hosting the AlloyDB database.
  • User: The user which will be used to authenticate with the AlloyDB server.
  • Password: The password which will be used to authenticate with the AlloyDB server.

You can also optionally set the following:

  • Database: The database to connect to when connecting to the AlloyDB Server. If this is not set, the user's default database will be used.
  • Port: The port of the server hosting the AlloyDB database. This property is set to 5432 by default.

Authenticating with Standard Authentication

Standard authentication (using the user/password combination supplied earlier) is the default form of authentication.

No further action is required to leverage Standard Authentication to connect.

Authenticating with pg_hba.conf Auth Schemes

There are additional methods of authentication available which must be enabled in the pg_hba.conf file on the AlloyDB server.

Find instructions about authentication setup on the AlloyDB Server here.

Authenticating with MD5 Authentication

This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to md5.

Authenticating with SASL Authentication

This authentication method must be enabled by setting the auth-method in the pg_hba.conf file to scram-sha-256.

Authenticating with Kerberos

The authentication with Kerberos is initiated by AlloyDB Server when the ∏ is trying to connect to it. You should set up Kerberos on the AlloyDB Server to activate this authentication method. Once you have Kerberos authentication set up on the AlloyDB Server, see the Kerberos section of the help documentation for details on how to authenticate with Kerberos.

/etc/odbc.ini or $HOME/.odbc.ini

[CData AlloyDB Source] Driver = CData ODBC Driver for AlloyDB Description = My Description User = alloydb Password = admin Database = alloydb Server = 127.0.0.1 Port = 5432

For specific information on using these configuration files, please refer to the help documentation (installed and found online).

You can follow the procedure below to install pyodbc and start accessing AlloyDB through Python objects.

Install pyodbc

You can use the pip utility to install the module:

pip install pyodbc

Be sure to import with the module with the following:

import pyodbc

Connect to AlloyDB Data in Python

You can now connect with an ODBC connection string or a DSN. Below is the syntax for a connection string:

cnxn = pyodbc.connect('DRIVER={CData ODBC Driver for AlloyDB};User=alloydb;Password=admin;Database=alloydb;Server=127.0.0.1;Port=5432')

Below is the syntax for a DSN:

cnxn = pyodbc.connect('DSN=CData AlloyDB Sys;')

Execute SQL to AlloyDB

Instantiate a Cursor and use the execute method of the Cursor class to execute any SQL statement.

cursor = cnxn.cursor()

Select

You can use fetchall, fetchone, and fetchmany to retrieve Rows returned from SELECT statements:

import pyodbc cursor = cnxn.cursor() cnxn = pyodbc.connect('DSN=CData AlloyDB Source;User=MyUser;Password=MyPassword') cursor.execute("SELECT ShipName, ShipCity FROM Orders WHERE ShipCountry = 'USA'") rows = cursor.fetchall() for row in rows: print(row.ShipName, row.ShipCity)

You can provide parameterized queries in a sequence or in the argument list:

cursor.execute( "SELECT ShipName, ShipCity FROM Orders WHERE ShipCountry = ?", 'USA',1)

Insert

INSERT commands also use the execute method; however, you must subsequently call the commit method after an insert or you will lose your changes:

cursor.execute("INSERT INTO Orders (ShipCountry) VALUES ('USA')") cnxn.commit()

Update and Delete

As with an insert, you must also call commit after calling execute for an update or delete:

cursor.execute("UPDATE Orders SET ShipCountry = 'USA'") cnxn.commit()

Metadata Discovery

You can use the getinfo method to retrieve data such as information about the data source and the capabilities of the driver. The getinfo method passes through input to the ODBC SQLGetInfo method.

cnxn.getinfo(pyodbc.SQL_DATA_SOURCE_NAME)

You are now ready to build Python apps in Linux/UNIX environments with connectivity to AlloyDB data, using the CData ODBC Driver for AlloyDB.