Vertica Query Result Export and Import using Python - python-2.7

Question

I want to copy certain data from a Vertica cluster (lets say a test cluster) to another Vertica cluster (lets say QA cluster). Manually I can do this by dumping the result of a query into a CSV file and then importing it on the other cluster. But, how can I do it on a Python script without using os or system commands. I want to do it purely using some Python module or adapter. As of now I am using python-vertica adapter, I am able to connect to Test cluster and get the data into a python list, but I am unable to export it to a CSV file natively using the adapter (i.e. without using python csv module). Also, how can I import the CSV file in my QA cluster using the same adapter (or a different vertica module for python)?

Answer 1

You can do it with COPY FROM VERTICA for simple problems. Read here for more info.
For python you can use in my template:
Environment:
python=2.7.x
vertica-python==0.7.3
Vertica Analytic Database v8.1.1-10
Source code example:
#!/usr/bin/env python2
# coding: UTF-8
import csv
import cStringIO
# connection info: username, password, etc
SRC_DB_INFO = {...}
DST_DB_INFO = {...}
csvbuffer = cStringIO.StringIO()
csvwriter = csv.writer(csvbuffer, delimiter='|', lineterminator='\n', quoting=csv.QUOTE_MINIMAL)
# establish connection to source database
connection = vertica_python.connect(**SRC_DB_INFO)
cursor = connection.cursor()
cursor.execute('SELECT * FROM A')
# convert data to csv format
for row in cursor.iterate():
csvwriter.writerow(row)
# cleanup
cursor.close()
connection.close()
# establish connection to destination database
connection = vertica_python.connect(**DST_DB_INFO)
cursor = connection.cursor()
# copy data
cursor.copy('COPY B FROM STDIN ABORT ON ERROR', csvbuffer.getvalue())
connection.commit()
# cleanup
cursor.close()
connection.close()