vertica-python

📢 08/14/2018: vertica-python becomes Vertica’s first officially supported open source database client, see the blog here.

0.6.x adds python3 support (unicode namedparams support is currently broken in python3, see issue 112)

0.5.x changes the connection method to accept kwargs instead of a dict to be more dbapi compliant. copy methods improved and consolidated in 0.5.1

0.4.x breaks some of the older query interfaces (row_handler callback, and connection.query). It replaces the row_handler callback with an iterate() method. Please see examples below If you are on 0.4.x, please upgrade to 0.4.6 as there are various bug fixes

vertica-python is a native Python adapter for the Vertica (http://www.vertica.com) database.

vertica-python is currently in beta stage; it has been tested for functionality and has a very basic test suite. Please use with caution, and feel free to submit issues and/or pull requests (after running the unit tests).

vertica-python has been tested with Vertica 6.1.2/7.0.0+ and Python 2.7/3.4.

Installation

If you're using pip >= 1.4 and you don't already have pytz installed:

pip install --pre pytz

If you're using pip >= 1.4 and you don't already have python-dateutil installed:

pip install --pre python-dateutil

To install vertica-python with pip:

pip install vertica-python

To install vertica-python with pip (with optional namedparams dependencies):

# see 'Using named parameters' section below
pip install 'vertica-python[namedparams]'

Source code for vertica-python can be found at:

https://github.com/vertica/vertica-python

Usage

Create connection

import vertica_python

conn_info = {'host': '127.0.0.1',
             'port': 5433,
             'user': 'some_user',
             'password': 'some_password',
             'database': 'a_database',
             # autogenerated session label by default,
             'session_label': 'some_label',
             # 10 minutes timeout on queries
             'read_timeout': 600,
             # default throw error on invalid UTF-8 results
             'unicode_error': 'strict',
             # SSL is disabled by default
             'ssl': False,
             # connection timeout is not enabled by default
             'connection_timeout': 5}

# simple connection, with manual close
connection = vertica_python.connect(**conn_info)
# do things
connection.close()

# using with for auto connection closing after usage
with vertica_python.connect(**conn_info) as connection:
    # do things

You can pass an ssl.SSLContext to ssl to customize the SSL connection options. For example,

import vertica_python
import ssl

ssl_context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
ssl_context.verify_mode = ssl.CERT_REQUIRED
ssl_context.check_hostname = True
ssl_context.load_verify_locations(cafile='/path/to/ca_file.pem')

conn_info = {'host': '127.0.0.1',
             'port': 5433,
             'user': 'some_user',
             'password': 'some_password',
             'database': 'a_database',
             'ssl': ssl_context}
connection = vertica_python.connect(**conn_info)

See more on SSL options here.

Logging is disabled by default if you do not pass values to both log_level and log_path. The default value of log_level is logging.WARNING. You can find all levels here. The default value of log_path is 'vertica_python.log', the log file will be in the current execution directory. For example,

import vertica_python
import logging

## Example 1: write DEBUG level logs to './vertica_python.log'
conn_info = {'host': '127.0.0.1',
             'port': 5433,
             'user': 'some_user',
             'password': 'some_password',
             'database': 'a_database',
             'log_level': logging.DEBUG}
with vertica_python.connect(**conn_info) as connection:
    # do things

## Example 2: write WARNING level logs to './path/to/logs/client.log'
conn_info = {'host': '127.0.0.1',
             'port': 5433,
             'user': 'some_user',
             'password': 'some_password',
             'database': 'a_database',
             'log_path': 'path/to/logs/client.log'}
with vertica_python.connect(**conn_info) as connection:
   # do things

## Example 3: write INFO level logs to '/home/admin/logs/vClient.log'
conn_info = {'host': '127.0.0.1',
             'port': 5433,
             'user': 'some_user',
             'password': 'some_password',
             'database': 'a_database',
             'log_level': logging.INFO,
             'log_path': '/home/admin/logs/vClient.log'}
with vertica_python.connect(**conn_info) as connection:
   # do things

Connection Failover: Supply a list of backup hosts to backup_server_node for the client to try if the primary host you specify in the connection parameters (host, port) is unreachable. Each item in the list should be either a host string (using default port 5433) or a (host, port) tuple. A host can be a host name or an IP address.

import vertica_python

conn_info = {'host': 'unreachable.server.com',
             'port': 888,
             'user': 'some_user',
             'password': 'some_password',
             'database': 'a_database',
             'backup_server_node': ['123.456.789.123', 'invalid.com', ('10.20.82.77', 6000)]}
connection = vertica_python.connect(**conn_info)

Connection Load Balancing helps automatically spread the overhead caused by client connections across the cluster by having hosts redirect client connections to other hosts. Both the server and the client need to enable load balancing for it to function. If the server disables connection load balancing, the load balancing request from client will be ignored.

import vertica_python

conn_info = {'host': '127.0.0.1',
             'port': 5433,
             'user': 'some_user',
             'password': 'some_password',
             'database': 'vdb',
             'connection_load_balance': True}

# Server enables load balancing
with connect(**conn_info) as conn:
    cur = conn.cursor()
    cur.execute("SELECT NODE_NAME FROM V_MONITOR.CURRENT_SESSION")
    print("Client connects to primary node:", cur.fetchone()[0])
    cur.execute("SELECT SET_LOAD_BALANCE_POLICY('ROUNDROBIN')")

with connect(**conn_info) as conn:
    cur = conn.cursor()
    cur.execute("SELECT NODE_NAME FROM V_MONITOR.CURRENT_SESSION")
    print("Client redirects to node:", cur.fetchone()[0])

## Output
#  Client connects to primary node: v_vdb_node0003
#  Client redirects to node: v_vdb_node0005

Stream query results:

cur = connection.cursor()
cur.execute("SELECT * FROM a_table LIMIT 2")

for row in cur.iterate():
    print(row)
# [ 1, 'some text', datetime.datetime(2014, 5, 18, 6, 47, 1, 928014) ]
# [ 2, 'something else', None ]

Streaming is recommended if you want to further process each row, save the results in a non-list/dict format (e.g. Pandas DataFrame), or save the results in a file.

In-memory results as list:

cur = connection.cursor()
cur.execute("SELECT * FROM a_table LIMIT 2")
cur.fetchall()
# [ [1, 'something'], [2, 'something_else'] ]

In-memory results as dictionary:

cur = connection.cursor('dict')
cur.execute("SELECT * FROM a_table LIMIT 2")
cur.fetchall()
# [ {'id': 1, 'value': 'something'}, {'id': 2, 'value': 'something_else'} ]
connection.close()

Query using named parameters:

# Using named parameter bindings requires psycopg2>=2.5.1 which is not includes with the base vertica_python requirements.

cur = connection.cursor()
cur.execute("SELECT * FROM a_table WHERE a = :propA b = :propB", {'propA': 1, 'propB': 'stringValue'})

cur.fetchall()
# [ [1, 'something'], [2, 'something_else'] ]

Insert and commits :

cur = connection.cursor()

# inline commit
cur.execute("INSERT INTO a_table (a, b) VALUES (1, 'aa'); commit;")

# commit in execution
cur.execute("INSERT INTO a_table (a, b) VALUES (1, 'aa')")
cur.execute("INSERT INTO a_table (a, b) VALUES (2, 'bb')")
cur.execute("commit;")

# connection.commit()
cur.execute("INSERT INTO a_table (a, b) VALUES (1, 'aa')")
connection.commit()

Copy :

cur = connection.cursor()
cur.copy("COPY test_copy (id, name) from stdin DELIMITER ',' ",  csv)

Where csv is either a string or a file-like object (specifically, any object with a read() method). If using a file, the data is streamed.

Rowcount oddities

vertica_python behaves a bit differently than dbapi when returning rowcounts.

After a select execution, the rowcount will be -1, indicating that the row count is unknown. The rowcount value will be updated as data is streamed.

cur.execute('SELECT 10 things')

cur.rowcount == -1  # indicates unknown rowcount

cur.fetchone()
cur.rowcount == 1
cur.fetchone()
cur.rowcount == 2
cur.fetchall()
cur.rowcount == 10

After an insert/update/delete, the rowcount will be returned as a single element row:

cur.execute("DELETE 3 things")

cur.rowcount == -1  # indicates unknown rowcount
cur.fetchone()[0] == 3

Nextset

If you execute multiple statements in a single call to execute(), you can use cursor.nextset() to retrieve all of the data.

cur.execute('SELECT 1; SELECT 2;')

cur.fetchone()
# [1]
cur.fetchone()
# None

cur.nextset()
# True

cur.fetchone()
# [2]
cur.fetchone()
# None

cur.nextset()
# None

UTF-8 encoding issues

While Vertica expects varchars stored to be UTF-8 encoded, sometimes invalid strings get into the database. You can specify how to handle reading these characters using the unicode_error connection option. This uses the same values as the unicode type (https://docs.python.org/2/library/functions.html#unicode)

cur = vertica_python.Connection({..., 'unicode_error': 'strict'}).cursor()
cur.execute(r"SELECT E'\xC2'")
cur.fetchone()
# caught 'utf8' codec can't decode byte 0xc2 in position 0: unexpected end of data

cur = vertica_python.Connection({..., 'unicode_error': 'replace'}).cursor()
cur.execute(r"SELECT E'\xC2'")
cur.fetchone()
# �

cur = vertica_python.Connection({..., 'unicode_error': 'ignore'}).cursor()
cur.execute(r"SELECT E'\xC2'")
cur.fetchone()
#

License

Apache 2.0 License, please see LICENSE for details.

Contributing guidelines

Have a bug or an idea? Please see CONTRIBUTING.md for details.

Acknowledgements

We would like to thank the contributors to the Ruby Vertica gem (https://github.com/sprsquish/vertica), as this project gave us inspiration and help in understanding Vertica's wire protocol. These contributors are:

alexmilk / vertica-python