Introduction

This package provides a client interface to query Presto a distributed SQL engine. It supports Python 2.7, 3.5, 3.6, and pypy.

Installation

$ pip install presto-client

Quick Start

Use the DBAPI interface to query Presto:

import presto
conn = presto.dbapi.connect(
    host='localhost',
    port=8080,
    user='the-user',
    catalog='the-catalog',
    schema='the-schema',
)
cur = conn.cursor()
cur.execute('SELECT * FROM system.runtime.nodes')
rows = cur.fetchall()

This will query the system.runtime.nodes system tables that shows the nodes in the Presto cluster.

The DBAPI implementation in presto.dbapi provides methods to retrieve fewer rows for example Cursorfetchone() or Cursor.fetchmany(). By default Cursor.fetchmany() fetches one row. Please set presto.dbapi.Cursor.arraysize accordingly.

Basic Authentication

The BasicAuthentication class can be used to connect to a LDAP-configured Presto cluster:

import presto
conn = presto.dbapi.connect(
    host='coordinator url',
    port=8443,
    user='the-user',
    catalog='the-catalog',
    schema='the-schema',
    http_scheme='https',
    auth=presto.auth.BasicAuthentication("principal id", "password"),
)
cur = conn.cursor()
cur.execute('SELECT * FROM system.runtime.nodes')
rows = cur.fetchall()

Transactions

The client runs by default in autocommit mode. To enable transactions, set isolation_level to a value different than IsolationLevel.AUTOCOMMIT:

import presto
from presto import transaction
with presto.dbapi.connect(
    host='localhost',
    port=8080,
    user='the-user',
    catalog='the-catalog',
    schema='the-schema',
    isolation_level=transaction.IsolationLevel.REPEATABLE_READ,
) as conn:
  cur = conn.cursor()
  cur.execute('INSERT INTO sometable VALUES (1, 2, 3)')
  cur.fetchone()
  cur.execute('INSERT INTO sometable VALUES (4, 5, 6)')
  cur.fetchone()

The transaction is created when the first SQL statement is executed. presto.dbapi.Connection.commit() will be automatically called when the code exits the with context and the queries succeed, otherwise `presto.dbapi.Connection.rollback()' will be called.

Development

Getting Started With Development

Start by forking the repository and then modify the code in your fork.

Clone the repository and go inside the code directory. Then you can get the version with ./setup.py --version.

We recommend that you use virtualenv for development:

$ virtualenv .venv
$ . .venv/bin/activate
# TODO add requirements.txt: pip install -r requirements.txt
$ pip install .

For development purpose, pip can reference the code you are modifying in a virtualenv:

$ pip install -e .[tests]

That way, you do not need to run pip install again to make your changes applied to the virtualenv.

When the code is ready, submit a Pull Request.

Code Style

For Python code, adhere to PEP 8.
Prefer code that is readable over one that is "clever".
When writing a Git commit message, follow these guidelines.

Running Tests

There is a helper scripts, run, that provides commands to run tests. Type ./run tests to run both unit and integration tests.

presto-python-client uses pytest for its tests. To run only unit tests, type:

$ pytest tests

Then you can pass options like --pdb or anything supported by pytest --help.

To run the tests with different versions of Python in managed virtualenvs, use tox (see the configuration in tox.ini):

$ tox

To run integration tests:

$ pytest integration_tests

They pull a Docker image and then run a container with a Presto server:

the image is named prestosql/presto:${PRESTO_VERSION}
the container is named presto-python-client-tests-{uuid4()[:7]}

Releasing

Set up your development environment.
Change version in presto/__init__.py.
Commit and create an annotated tag (git tag -m '' current_version)

Run the following:

. .venv/bin/activate &&
pip install twine &&
rm -rf dist/ &&
./setup.py sdist bdist_wheel &&
twine upload dist/* &&
open https://pypi.org/project/presto-client/ &&
echo "Released!"

Push the branch and the tag (git push upstream master current_version)
Send release announcement.

Need Help?

Feel free to create an issue as it make your request visible to other users and contributors.

If an interactive discussion would be better or if you just want to hangout and chat about the Presto Python client, you can join us on the #python-client channel on Presto Slack.

OneRaynyDay / presto-python-client