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Impala Python Connector
Python Connector Libraries for Apache Impala Data Connectivity. Integrate Apache Impala with popular Python tools like Pandas, SQLAlchemy, Dash & petl.
How to use SQLAlchemy ORM to access Impala Data in Python
Create Python applications and scripts that use SQLAlchemy Object-Relational Mappings of Impala data.
The rich ecosystem of Python modules lets you get to work quickly and integrate your systems effectively. With the CData Python Connector for Impala and the SQLAlchemy toolkit, you can build Impala-connected Python applications and scripts. This article shows how to use SQLAlchemy to connect to Impala data to query, update, delete, and insert Impala data.
With built-in optimized data processing, the CData Python Connector offers unmatched performance for interacting with live Impala data in Python. When you issue complex SQL queries from Impala, the CData Connector pushes supported SQL operations, like filters and aggregations, directly to Impala and utilizes the embedded SQL engine to process unsupported operations client-side (often SQL functions and JOIN operations).
Connecting to Impala Data
Connecting to Impala data looks just like connecting to any relational data source. Create a connection string using the required connection properties. For this article, you will pass the connection string as a parameter to the create_engine function.
In order to connect to Apache Impala, set the Server, Port, and ProtocolVersion. You may optionally specify a default Database. To connect using alternative methods, such as NOSASL, LDAP, or Kerberos, refer to the online Help documentation.
Follow the procedure below to install SQLAlchemy and start accessing Impala through Python objects.
Install Required Modules
Use the pip utility to install the SQLAlchemy toolkit and SQLAlchemy ORM package:
pip install sqlalchemy
pip install sqlalchemy.orm
Be sure to import the appropriate modules:
from sqlalchemy import create_engine, String, Column
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
Model Impala Data in Python
You can now connect with a connection string. Use the create_engine function to create an Engine for working with Impala data.
NOTE: Users should URL encode the any connection string properties that include special characters. For more information, refer to the SQL Alchemy documentation.
engine = create_engine("apacheimpala:///?Server=127.0.0.1&Port=21050")
Declare a Mapping Class for Impala Data
After establishing the connection, declare a mapping class for the table you wish to model in the ORM (in this article, we will model the Customers table). Use the sqlalchemy.ext.declarative.declarative_base function and create a new class with some or all of the fields (columns) defined.
base = declarative_base()
class Customers(base):
__tablename__ = "Customers"
City = Column(String,primary_key=True)
CompanyName = Column(String)
...
Query Impala Data
With the mapping class prepared, you can use a session object to query the data source. After binding the Engine to the session, provide the mapping class to the session query method.
Using the query Method
engine = create_engine("apacheimpala:///?Server=127.0.0.1&Port=21050")
factory = sessionmaker(bind=engine)
session = factory()
for instance in session.query(Customers).filter_by(Country="US"):
print("City: ", instance.City)
print("CompanyName: ", instance.CompanyName)
print("---------")
Alternatively, you can use the execute method with the appropriate table object. The code below works with an active session.
Using the execute Method
Customers_table = Customers.metadata.tables["Customers"]
for instance in session.execute(Customers_table.select().where(Customers_table.c.Country == "US")):
print("City: ", instance.City)
print("CompanyName: ", instance.CompanyName)
print("---------")
For examples of more complex querying, including JOINs, aggregations, limits, and more, refer to the Help documentation for the extension.
Insert Impala Data
To insert Impala data, define an instance of the mapped class and add it to the active session. Call the commit function on the session to push all added instances to Impala.
new_rec = Customers(City="placeholder", Country="US")
session.add(new_rec)
session.commit()
Update Impala Data
To update Impala data, fetch the desired record(s) with a filter query. Then, modify the values of the fields and call the commit function on the session to push the modified record to Impala.
updated_rec = session.query(Customers).filter_by(SOME_ID_COLUMN="SOME_ID_VALUE").first()
updated_rec.Country = "US"
session.commit()
Delete Impala Data
To delete Impala data, fetch the desired record(s) with a filter query. Then delete the record with the active session and call the commit function on the session to perform the delete operation on the provided records (rows).
deleted_rec = session.query(Customers).filter_by(SOME_ID_COLUMN="SOME_ID_VALUE").first()
session.delete(deleted_rec)
session.commit()
Free Trial & More Information
Download a free, 30-day trial of the CData Python Connector for Impala to start building Python apps and scripts with connectivity to Impala data. Reach out to our Support Team if you have any questions.
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