examples/src/main/python/sql.py

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import os

from pyspark import SparkContext
from pyspark.sql import SQLContext
from pyspark.sql.types import Row, StructField, StructType, StringType, IntegerType


if __name__ == "__main__":
    sc = SparkContext(appName="PythonSQL")
    sqlContext = SQLContext(sc)

    # RDD is created from a list of rows
    some_rdd = sc.parallelize([Row(name="John", age=19),
                              Row(name="Smith", age=23),
                              Row(name="Sarah", age=18)])
    # Infer schema from the first row, create a DataFrame and print the schema
    some_df = sqlContext.createDataFrame(some_rdd)
    some_df.printSchema()

    # Another RDD is created from a list of tuples
    another_rdd = sc.parallelize([("John", 19), ("Smith", 23), ("Sarah", 18)])
    # Schema with two fields - person_name and person_age
    schema = StructType([StructField("person_name", StringType(), False),
                        StructField("person_age", IntegerType(), False)])
    # Create a DataFrame by applying the schema to the RDD and print the schema
    another_df = sqlContext.createDataFrame(another_rdd, schema)
    another_df.printSchema()
    # root
    #  |-- age: integer (nullable = true)
    #  |-- name: string (nullable = true)

    # A JSON dataset is pointed to by path.
    # The path can be either a single text file or a directory storing text files.
    path = os.path.join(os.environ['SPARK_HOME'], "examples/src/main/resources/people.json")
    # Create a DataFrame from the file(s) pointed to by path
    people = sqlContext.jsonFile(path)
    # root
    #  |-- person_name: string (nullable = false)
    #  |-- person_age: integer (nullable = false)

    # The inferred schema can be visualized using the printSchema() method.
    people.printSchema()
    # root
    #  |-- age: IntegerType
    #  |-- name: StringType

    # Register this DataFrame as a table.
    people.registerAsTable("people")

    # SQL statements can be run by using the sql methods provided by sqlContext
    teenagers = sqlContext.sql("SELECT name FROM people WHERE age >= 13 AND age <= 19")

    for each in teenagers.collect():
        print each[0]

    sc.stop()