无法使用pyspark shell中的jdbc连接到postgres

Question

I am using standalone cluster on my local windows and trying to load data from one of our server using following code -

from pyspark.sql import SQLContext
sqlContext = SQLContext(sc)
df = sqlContext.load(source="jdbc", url="jdbc:postgresql://host/dbname", dbtable="schema.tablename")

I have set the SPARK_CLASSPATH as -

os.environ['SPARK_CLASSPATH'] = "C:\Users\ACERNEW3\Desktop\Spark\spark-1.3.0-bin-hadoop2.4\postgresql-9.2-1002.jdbc3.jar"

While executing sqlContext.load, it throws error mentioning "No suitable driver found for jdbc:postgresql". I have tried searching web, but not able to find solution.

Answer 1

May be it will be helpful.

In my environment SPARK_CLASSPATH contains path to postgresql connector

from pyspark import SparkContext, SparkConf
from pyspark.sql import DataFrameReader, SQLContext
import os

sparkClassPath = os.getenv('SPARK_CLASSPATH', '/path/to/connector/postgresql-42.1.4.jar')

# Populate configuration
conf = SparkConf()
conf.setAppName('application')
conf.set('spark.jars', 'file:%s' % sparkClassPath)
conf.set('spark.executor.extraClassPath', sparkClassPath)
conf.set('spark.driver.extraClassPath', sparkClassPath)
# Uncomment line below and modify ip address if you need to use cluster on different IP address
#conf.set('spark.master', 'spark://127.0.0.1:7077')

sc = SparkContext(conf=conf)
sqlContext = SQLContext(sc)

url = 'postgresql://127.0.0.1:5432/postgresql'
properties = {'user':'username', 'password':'password'}

df = DataFrameReader(sqlContext).jdbc(url='jdbc:%s' % url, table='tablename', properties=properties)

df.printSchema()
df.show()

This piece of code allows to use pyspark where you need. For example, I've used it in Django project.

Answer 2

I had the same problem with mysql, and was never able to get it to work with the SPARK_CLASSPATH approach. However I did get it to work with extra command line arguments, see the answer to this question

To avoid having to click through to get it working, here's what you have to do:

pyspark --conf spark.executor.extraClassPath=<jdbc.jar> --driver-class-path <jdbc.jar> --jars <jdbc.jar> --master <master-URL>