python/pyspark/sql/context.py

#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

import sys
import warnings
import json

if sys.version >= '3':
    basestring = unicode = str
else:
    from itertools import imap as map

from py4j.protocol import Py4JError

from pyspark.rdd import RDD, _prepare_for_python_RDD, ignore_unicode_prefix
from pyspark.serializers import AutoBatchedSerializer, PickleSerializer
from pyspark.sql import since
from pyspark.sql.types import Row, StringType, StructType, _verify_type, \
    _infer_schema, _has_nulltype, _merge_type, _create_converter
from pyspark.sql.dataframe import DataFrame
from pyspark.sql.readwriter import DataFrameReader
from pyspark.sql.utils import install_exception_handler
from pyspark.sql.functions import UserDefinedFunction

try:
    import pandas
    has_pandas = True
except Exception:
    has_pandas = False

__all__ = ["SQLContext", "HiveContext", "UDFRegistration"]


def _monkey_patch_RDD(sqlContext):
    def toDF(self, schema=None, sampleRatio=None):
        """
        Converts current :class:`RDD` into a :class:`DataFrame`

        This is a shorthand for ``sqlContext.createDataFrame(rdd, schema, sampleRatio)``

        :param schema: a StructType or list of names of columns
        :param samplingRatio: the sample ratio of rows used for inferring
        :return: a DataFrame

        >>> rdd.toDF().collect()
        [Row(name=u'Alice', age=1)]
        """
        return sqlContext.createDataFrame(self, schema, sampleRatio)

    RDD.toDF = toDF


class SQLContext(object):
    """Main entry point for Spark SQL functionality.

    A SQLContext can be used create :class:`DataFrame`, register :class:`DataFrame` as
    tables, execute SQL over tables, cache tables, and read parquet files.

    :param sparkContext: The :class:`SparkContext` backing this SQLContext.
    :param sqlContext: An optional JVM Scala SQLContext. If set, we do not instantiate a new
        SQLContext in the JVM, instead we make all calls to this object.
    """

    _instantiatedContext = None

    @ignore_unicode_prefix
    def __init__(self, sparkContext, sqlContext=None):
        """Creates a new SQLContext.

        >>> from datetime import datetime
        >>> sqlContext = SQLContext(sc)
        >>> allTypes = sc.parallelize([Row(i=1, s="string", d=1.0, l=1,
        ...     b=True, list=[1, 2, 3], dict={"s": 0}, row=Row(a=1),
        ...     time=datetime(2014, 8, 1, 14, 1, 5))])
        >>> df = allTypes.toDF()
        >>> df.registerTempTable("allTypes")
        >>> sqlContext.sql('select i+1, d+1, not b, list[1], dict["s"], time, row.a '
        ...            'from allTypes where b and i > 0').collect()
        [Row(_c0=2, _c1=2.0, _c2=False, _c3=2, _c4=0, \
            time=datetime.datetime(2014, 8, 1, 14, 1, 5), a=1)]
        >>> df.map(lambda x: (x.i, x.s, x.d, x.l, x.b, x.time, x.row.a, x.list)).collect()
        [(1, u'string', 1.0, 1, True, datetime.datetime(2014, 8, 1, 14, 1, 5), 1, [1, 2, 3])]
        """
        self._sc = sparkContext
        self._jsc = self._sc._jsc
        self._jvm = self._sc._jvm
        self._scala_SQLContext = sqlContext
        _monkey_patch_RDD(self)
        install_exception_handler()
        SQLContext._instantiatedContext = self

    @property
    def _ssql_ctx(self):
        """Accessor for the JVM Spark SQL context.

        Subclasses can override this property to provide their own
        JVM Contexts.
        """
        if self._scala_SQLContext is None:
            self._scala_SQLContext = self._jvm.SQLContext(self._jsc.sc())
        return self._scala_SQLContext

    @since(1.3)
    def setConf(self, key, value):
        """Sets the given Spark SQL configuration property.
        """
        self._ssql_ctx.setConf(key, value)

    @since(1.3)
    def getConf(self, key, defaultValue):
        """Returns the value of Spark SQL configuration property for the given key.

        If the key is not set, returns defaultValue.
        """
        return self._ssql_ctx.getConf(key, defaultValue)

    @property
    @since("1.3.1")
    def udf(self):
        """Returns a :class:`UDFRegistration` for UDF registration.

        :return: :class:`UDFRegistration`
        """
        return UDFRegistration(self)

    @since(1.4)
    def range(self, start, end=None, step=1, numPartitions=None):
        """
        Create a :class:`DataFrame` with single LongType column named `id`,
        containing elements in a range from `start` to `end` (exclusive) with
        step value `step`.

        :param start: the start value
        :param end: the end value (exclusive)
        :param step: the incremental step (default: 1)
        :param numPartitions: the number of partitions of the DataFrame
        :return: :class:`DataFrame`

        >>> sqlContext.range(1, 7, 2).collect()
        [Row(id=1), Row(id=3), Row(id=5)]

        If only one argument is specified, it will be used as the end value.

        >>> sqlContext.range(3).collect()
        [Row(id=0), Row(id=1), Row(id=2)]
        """
        if numPartitions is None:
            numPartitions = self._sc.defaultParallelism

        if end is None:
            jdf = self._ssql_ctx.range(0, int(start), int(step), int(numPartitions))
        else:
            jdf = self._ssql_ctx.range(int(start), int(end), int(step), int(numPartitions))

        return DataFrame(jdf, self)

    @ignore_unicode_prefix
    @since(1.2)
    def registerFunction(self, name, f, returnType=StringType()):
        """Registers a lambda function as a UDF so it can be used in SQL statements.

        In addition to a name and the function itself, the return type can be optionally specified.
        When the return type is not given it default to a string and conversion will automatically
        be done.  For any other return type, the produced object must match the specified type.

        :param name: name of the UDF
        :param samplingRatio: lambda function
        :param returnType: a :class:`DataType` object

        >>> sqlContext.registerFunction("stringLengthString", lambda x: len(x))
        >>> sqlContext.sql("SELECT stringLengthString('test')").collect()
        [Row(_c0=u'4')]

        >>> from pyspark.sql.types import IntegerType
        >>> sqlContext.registerFunction("stringLengthInt", lambda x: len(x), IntegerType())
        >>> sqlContext.sql("SELECT stringLengthInt('test')").collect()
        [Row(_c0=4)]

        >>> from pyspark.sql.types import IntegerType
        >>> sqlContext.udf.register("stringLengthInt", lambda x: len(x), IntegerType())
        >>> sqlContext.sql("SELECT stringLengthInt('test')").collect()
        [Row(_c0=4)]
        """
        udf = UserDefinedFunction(f, returnType, name)
        self._ssql_ctx.udf().registerPython(name, udf._judf)

    def _inferSchemaFromList(self, data):
        """
        Infer schema from list of Row or tuple.

        :param data: list of Row or tuple
        :return: StructType
        """
        if not data:
            raise ValueError("can not infer schema from empty dataset")
        first = data[0]
        if type(first) is dict:
            warnings.warn("inferring schema from dict is deprecated,"
                          "please use pyspark.sql.Row instead")
        schema = _infer_schema(first)
        if _has_nulltype(schema):
            for r in data:
                schema = _merge_type(schema, _infer_schema(r))
                if not _has_nulltype(schema):
                    break
            else:
                raise ValueError("Some of types cannot be determined after inferring")
        return schema

    def _inferSchema(self, rdd, samplingRatio=None):
        """
        Infer schema from an RDD of Row or tuple.

        :param rdd: an RDD of Row or tuple
        :param samplingRatio: sampling ratio, or no sampling (default)
        :return: StructType
        """
        first = rdd.first()
        if not first:
            raise ValueError("The first row in RDD is empty, "
                             "can not infer schema")
        if type(first) is dict:
            warnings.warn("Using RDD of dict to inferSchema is deprecated. "
                          "Use pyspark.sql.Row instead")

        if samplingRatio is None:
            schema = _infer_schema(first)
            if _has_nulltype(schema):
                for row in rdd.take(100)[1:]:
                    schema = _merge_type(schema, _infer_schema(row))
                    if not _has_nulltype(schema):
                        break
                else:
                    raise ValueError("Some of types cannot be determined by the "
                                     "first 100 rows, please try again with sampling")
        else:
            if samplingRatio < 0.99:
                rdd = rdd.sample(False, float(samplingRatio))
            schema = rdd.map(_infer_schema).reduce(_merge_type)
        return schema

    @ignore_unicode_prefix
    def inferSchema(self, rdd, samplingRatio=None):
        """
        .. note:: Deprecated in 1.3, use :func:`createDataFrame` instead.
        """
        warnings.warn("inferSchema is deprecated, please use createDataFrame instead.")

        if isinstance(rdd, DataFrame):
            raise TypeError("Cannot apply schema to DataFrame")

        return self.createDataFrame(rdd, None, samplingRatio)

    @ignore_unicode_prefix
    def applySchema(self, rdd, schema):
        """
        .. note:: Deprecated in 1.3, use :func:`createDataFrame` instead.
        """
        warnings.warn("applySchema is deprecated, please use createDataFrame instead")

        if isinstance(rdd, DataFrame):
            raise TypeError("Cannot apply schema to DataFrame")

        if not isinstance(schema, StructType):
            raise TypeError("schema should be StructType, but got %s" % type(schema))

        return self.createDataFrame(rdd, schema)

    def _createFromRDD(self, rdd, schema, samplingRatio):
        """
        Create an RDD for DataFrame from an existing RDD, returns the RDD and schema.
        """
        if schema is None or isinstance(schema, (list, tuple)):
            struct = self._inferSchema(rdd, samplingRatio)
            converter = _create_converter(struct)
            rdd = rdd.map(converter)
            if isinstance(schema, (list, tuple)):
                for i, name in enumerate(schema):
                    struct.fields[i].name = name
                    struct.names[i] = name
            schema = struct

        elif isinstance(schema, StructType):
            # take the first few rows to verify schema
            rows = rdd.take(10)
            for row in rows:
                _verify_type(row, schema)

        else:
            raise TypeError("schema should be StructType or list or None, but got: %s" % schema)

        # convert python objects to sql data
        rdd = rdd.map(schema.toInternal)
        return rdd, schema

    def _createFromLocal(self, data, schema):
        """
        Create an RDD for DataFrame from an list or pandas.DataFrame, returns
        the RDD and schema.
        """
        if has_pandas and isinstance(data, pandas.DataFrame):
            if schema is None:
                schema = [str(x) for x in data.columns]
            data = [r.tolist() for r in data.to_records(index=False)]

        # make sure data could consumed multiple times
        if not isinstance(data, list):
            data = list(data)

        if schema is None or isinstance(schema, (list, tuple)):
            struct = self._inferSchemaFromList(data)
            if isinstance(schema, (list, tuple)):
                for i, name in enumerate(schema):
                    struct.fields[i].name = name
                    struct.names[i] = name
            schema = struct

        elif isinstance(schema, StructType):
            for row in data:
                _verify_type(row, schema)

        else:
            raise TypeError("schema should be StructType or list or None, but got: %s" % schema)

        # convert python objects to sql data
        data = [schema.toInternal(row) for row in data]
        return self._sc.parallelize(data), schema

    @since(1.3)
    @ignore_unicode_prefix
    def createDataFrame(self, data, schema=None, samplingRatio=None):
        """
        Creates a :class:`DataFrame` from an :class:`RDD` of :class:`tuple`/:class:`list`,
        list or :class:`pandas.DataFrame`.

        When ``schema`` is a list of column names, the type of each column
        will be inferred from ``data``.

        When ``schema`` is ``None``, it will try to infer the schema (column names and types)
        from ``data``, which should be an RDD of :class:`Row`,
        or :class:`namedtuple`, or :class:`dict`.

        If schema inference is needed, ``samplingRatio`` is used to determined the ratio of
        rows used for schema inference. The first row will be used if ``samplingRatio`` is ``None``.

        :param data: an RDD of :class:`Row`/:class:`tuple`/:class:`list`/:class:`dict`,
            :class:`list`, or :class:`pandas.DataFrame`.
        :param schema: a :class:`StructType` or list of column names. default None.
        :param samplingRatio: the sample ratio of rows used for inferring
        :return: :class:`DataFrame`

        >>> l = [('Alice', 1)]
        >>> sqlContext.createDataFrame(l).collect()
        [Row(_1=u'Alice', _2=1)]
        >>> sqlContext.createDataFrame(l, ['name', 'age']).collect()
        [Row(name=u'Alice', age=1)]

        >>> d = [{'name': 'Alice', 'age': 1}]
        >>> sqlContext.createDataFrame(d).collect()
        [Row(age=1, name=u'Alice')]

        >>> rdd = sc.parallelize(l)
        >>> sqlContext.createDataFrame(rdd).collect()
        [Row(_1=u'Alice', _2=1)]
        >>> df = sqlContext.createDataFrame(rdd, ['name', 'age'])
        >>> df.collect()
        [Row(name=u'Alice', age=1)]

        >>> from pyspark.sql import Row
        >>> Person = Row('name', 'age')
        >>> person = rdd.map(lambda r: Person(*r))
        >>> df2 = sqlContext.createDataFrame(person)
        >>> df2.collect()
        [Row(name=u'Alice', age=1)]

        >>> from pyspark.sql.types import *
        >>> schema = StructType([
        ...    StructField("name", StringType(), True),
        ...    StructField("age", IntegerType(), True)])
        >>> df3 = sqlContext.createDataFrame(rdd, schema)
        >>> df3.collect()
        [Row(name=u'Alice', age=1)]

        >>> sqlContext.createDataFrame(df.toPandas()).collect()  # doctest: +SKIP
        [Row(name=u'Alice', age=1)]
        >>> sqlContext.createDataFrame(pandas.DataFrame([[1, 2]]).collect())  # doctest: +SKIP
        [Row(0=1, 1=2)]
        """
        if isinstance(data, DataFrame):
            raise TypeError("data is already a DataFrame")

        if isinstance(data, RDD):
            rdd, schema = self._createFromRDD(data, schema, samplingRatio)
        else:
            rdd, schema = self._createFromLocal(data, schema)
        jrdd = self._jvm.SerDeUtil.toJavaArray(rdd._to_java_object_rdd())
        jdf = self._ssql_ctx.applySchemaToPythonRDD(jrdd.rdd(), schema.json())
        df = DataFrame(jdf, self)
        df._schema = schema
        return df

    @since(1.3)
    def registerDataFrameAsTable(self, df, tableName):
        """Registers the given :class:`DataFrame` as a temporary table in the catalog.

        Temporary tables exist only during the lifetime of this instance of :class:`SQLContext`.

        >>> sqlContext.registerDataFrameAsTable(df, "table1")
        """
        if (df.__class__ is DataFrame):
            self._ssql_ctx.registerDataFrameAsTable(df._jdf, tableName)
        else:
            raise ValueError("Can only register DataFrame as table")

    def parquetFile(self, *paths):
        """Loads a Parquet file, returning the result as a :class:`DataFrame`.

        .. note:: Deprecated in 1.4, use :func:`DataFrameReader.parquet` instead.

        >>> sqlContext.parquetFile('python/test_support/sql/parquet_partitioned').dtypes
        [('name', 'string'), ('year', 'int'), ('month', 'int'), ('day', 'int')]
        """
        warnings.warn("parquetFile is deprecated. Use read.parquet() instead.")
        gateway = self._sc._gateway
        jpaths = gateway.new_array(gateway.jvm.java.lang.String, len(paths))
        for i in range(0, len(paths)):
            jpaths[i] = paths[i]
        jdf = self._ssql_ctx.parquetFile(jpaths)
        return DataFrame(jdf, self)

    def jsonFile(self, path, schema=None, samplingRatio=1.0):
        """Loads a text file storing one JSON object per line as a :class:`DataFrame`.

        .. note:: Deprecated in 1.4, use :func:`DataFrameReader.json` instead.

        >>> sqlContext.jsonFile('python/test_support/sql/people.json').dtypes
        [('age', 'bigint'), ('name', 'string')]
        """
        warnings.warn("jsonFile is deprecated. Use read.json() instead.")
        if schema is None:
            df = self._ssql_ctx.jsonFile(path, samplingRatio)
        else:
            scala_datatype = self._ssql_ctx.parseDataType(schema.json())
            df = self._ssql_ctx.jsonFile(path, scala_datatype)
        return DataFrame(df, self)

    @ignore_unicode_prefix
    @since(1.0)
    def jsonRDD(self, rdd, schema=None, samplingRatio=1.0):
        """Loads an RDD storing one JSON object per string as a :class:`DataFrame`.

        If the schema is provided, applies the given schema to this JSON dataset.
        Otherwise, it samples the dataset with ratio ``samplingRatio`` to determine the schema.

        >>> df1 = sqlContext.jsonRDD(json)
        >>> df1.first()
        Row(field1=1, field2=u'row1', field3=Row(field4=11, field5=None), field6=None)

        >>> df2 = sqlContext.jsonRDD(json, df1.schema)
        >>> df2.first()
        Row(field1=1, field2=u'row1', field3=Row(field4=11, field5=None), field6=None)

        >>> from pyspark.sql.types import *
        >>> schema = StructType([
        ...     StructField("field2", StringType()),
        ...     StructField("field3",
        ...                 StructType([StructField("field5", ArrayType(IntegerType()))]))
        ... ])
        >>> df3 = sqlContext.jsonRDD(json, schema)
        >>> df3.first()
        Row(field2=u'row1', field3=Row(field5=None))
        """

        def func(iterator):
            for x in iterator:
                if not isinstance(x, basestring):
                    x = unicode(x)
                if isinstance(x, unicode):
                    x = x.encode("utf-8")
                yield x
        keyed = rdd.mapPartitions(func)
        keyed._bypass_serializer = True
        jrdd = keyed._jrdd.map(self._jvm.BytesToString())
        if schema is None:
            df = self._ssql_ctx.jsonRDD(jrdd.rdd(), samplingRatio)
        else:
            scala_datatype = self._ssql_ctx.parseDataType(schema.json())
            df = self._ssql_ctx.jsonRDD(jrdd.rdd(), scala_datatype)
        return DataFrame(df, self)

    def load(self, path=None, source=None, schema=None, **options):
        """Returns the dataset in a data source as a :class:`DataFrame`.

        .. note:: Deprecated in 1.4, use :func:`DataFrameReader.load` instead.
        """
        warnings.warn("load is deprecated. Use read.load() instead.")
        return self.read.load(path, source, schema, **options)

    @since(1.3)
    def createExternalTable(self, tableName, path=None, source=None, schema=None, **options):
        """Creates an external table based on the dataset in a data source.

        It returns the DataFrame associated with the external table.

        The data source is specified by the ``source`` and a set of ``options``.
        If ``source`` is not specified, the default data source configured by
        ``spark.sql.sources.default`` will be used.

        Optionally, a schema can be provided as the schema of the returned :class:`DataFrame` and
        created external table.

        :return: :class:`DataFrame`
        """
        if path is not None:
            options["path"] = path
        if source is None:
            source = self.getConf("spark.sql.sources.default",
                                  "org.apache.spark.sql.parquet")
        if schema is None:
            df = self._ssql_ctx.createExternalTable(tableName, source, options)
        else:
            if not isinstance(schema, StructType):
                raise TypeError("schema should be StructType")
            scala_datatype = self._ssql_ctx.parseDataType(schema.json())
            df = self._ssql_ctx.createExternalTable(tableName, source, scala_datatype,
                                                    options)
        return DataFrame(df, self)

    @ignore_unicode_prefix
    @since(1.0)
    def sql(self, sqlQuery):
        """Returns a :class:`DataFrame` representing the result of the given query.

        :return: :class:`DataFrame`

        >>> sqlContext.registerDataFrameAsTable(df, "table1")
        >>> df2 = sqlContext.sql("SELECT field1 AS f1, field2 as f2 from table1")
        >>> df2.collect()
        [Row(f1=1, f2=u'row1'), Row(f1=2, f2=u'row2'), Row(f1=3, f2=u'row3')]
        """
        return DataFrame(self._ssql_ctx.sql(sqlQuery), self)

    @since(1.0)
    def table(self, tableName):
        """Returns the specified table as a :class:`DataFrame`.

        :return: :class:`DataFrame`

        >>> sqlContext.registerDataFrameAsTable(df, "table1")
        >>> df2 = sqlContext.table("table1")
        >>> sorted(df.collect()) == sorted(df2.collect())
        True
        """
        return DataFrame(self._ssql_ctx.table(tableName), self)

    @ignore_unicode_prefix
    @since(1.3)
    def tables(self, dbName=None):
        """Returns a :class:`DataFrame` containing names of tables in the given database.

        If ``dbName`` is not specified, the current database will be used.

        The returned DataFrame has two columns: ``tableName`` and ``isTemporary``
        (a column with :class:`BooleanType` indicating if a table is a temporary one or not).

        :param dbName: string, name of the database to use.
        :return: :class:`DataFrame`

        >>> sqlContext.registerDataFrameAsTable(df, "table1")
        >>> df2 = sqlContext.tables()
        >>> df2.filter("tableName = 'table1'").first()
        Row(tableName=u'table1', isTemporary=True)
        """
        if dbName is None:
            return DataFrame(self._ssql_ctx.tables(), self)
        else:
            return DataFrame(self._ssql_ctx.tables(dbName), self)

    @since(1.3)
    def tableNames(self, dbName=None):
        """Returns a list of names of tables in the database ``dbName``.

        :param dbName: string, name of the database to use. Default to the current database.
        :return: list of table names, in string

        >>> sqlContext.registerDataFrameAsTable(df, "table1")
        >>> "table1" in sqlContext.tableNames()
        True
        >>> "table1" in sqlContext.tableNames("db")
        True
        """
        if dbName is None:
            return [name for name in self._ssql_ctx.tableNames()]
        else:
            return [name for name in self._ssql_ctx.tableNames(dbName)]

    @since(1.0)
    def cacheTable(self, tableName):
        """Caches the specified table in-memory."""
        self._ssql_ctx.cacheTable(tableName)

    @since(1.0)
    def uncacheTable(self, tableName):
        """Removes the specified table from the in-memory cache."""
        self._ssql_ctx.uncacheTable(tableName)

    @since(1.3)
    def clearCache(self):
        """Removes all cached tables from the in-memory cache. """
        self._ssql_ctx.clearCache()

    @property
    @since(1.4)
    def read(self):
        """
        Returns a :class:`DataFrameReader` that can be used to read data
        in as a :class:`DataFrame`.

        :return: :class:`DataFrameReader`
        """
        return DataFrameReader(self)


class HiveContext(SQLContext):
    """A variant of Spark SQL that integrates with data stored in Hive.

    Configuration for Hive is read from ``hive-site.xml`` on the classpath.
    It supports running both SQL and HiveQL commands.

    :param sparkContext: The SparkContext to wrap.
    :param hiveContext: An optional JVM Scala HiveContext. If set, we do not instantiate a new
        :class:`HiveContext` in the JVM, instead we make all calls to this object.
    """

    def __init__(self, sparkContext, hiveContext=None):
        SQLContext.__init__(self, sparkContext)
        if hiveContext:
            self._scala_HiveContext = hiveContext

    @property
    def _ssql_ctx(self):
        try:
            if not hasattr(self, '_scala_HiveContext'):
                self._scala_HiveContext = self._get_hive_ctx()
            return self._scala_HiveContext
        except Py4JError as e:
            raise Exception("You must build Spark with Hive. "
                            "Export 'SPARK_HIVE=true' and run "
                            "build/sbt assembly", e)

    def _get_hive_ctx(self):
        return self._jvm.HiveContext(self._jsc.sc())

    def refreshTable(self, tableName):
        """Invalidate and refresh all the cached the metadata of the given
        table. For performance reasons, Spark SQL or the external data source
        library it uses might cache certain metadata about a table, such as the
        location of blocks. When those change outside of Spark SQL, users should
        call this function to invalidate the cache.
        """
        self._ssql_ctx.refreshTable(tableName)


class UDFRegistration(object):
    """Wrapper for user-defined function registration."""

    def __init__(self, sqlContext):
        self.sqlContext = sqlContext

    def register(self, name, f, returnType=StringType()):
        return self.sqlContext.registerFunction(name, f, returnType)

    register.__doc__ = SQLContext.registerFunction.__doc__


def _test():
    import os
    import doctest
    from pyspark.context import SparkContext
    from pyspark.sql import Row, SQLContext
    import pyspark.sql.context

    os.chdir(os.environ["SPARK_HOME"])

    globs = pyspark.sql.context.__dict__.copy()
    sc = SparkContext('local[4]', 'PythonTest')
    globs['sc'] = sc
    globs['sqlContext'] = SQLContext(sc)
    globs['rdd'] = rdd = sc.parallelize(
        [Row(field1=1, field2="row1"),
         Row(field1=2, field2="row2"),
         Row(field1=3, field2="row3")]
    )
    globs['df'] = rdd.toDF()
    jsonStrings = [
        '{"field1": 1, "field2": "row1", "field3":{"field4":11}}',
        '{"field1" : 2, "field3":{"field4":22, "field5": [10, 11]},'
        '"field6":[{"field7": "row2"}]}',
        '{"field1" : null, "field2": "row3", '
        '"field3":{"field4":33, "field5": []}}'
    ]
    globs['jsonStrings'] = jsonStrings
    globs['json'] = sc.parallelize(jsonStrings)
    (failure_count, test_count) = doctest.testmod(
        pyspark.sql.context, globs=globs,
        optionflags=doctest.ELLIPSIS | doctest.NORMALIZE_WHITESPACE)
    globs['sc'].stop()
    if failure_count:
        exit(-1)


if __name__ == "__main__":
    _test()