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Spark Sql：TypeError（ "StructType can not accept object in type％s"％type（obj））

現在、PyODBCを使用してSQL Serverからデータをプルし、ほぼリアルタイム（NRT）の方法でHiveのテーブルに挿入しようとしています。

ソースから単一の行を取得し、List [Strings]に変換してプログラムでスキーマを作成しましたが、DataFrameの作成中にSparkがStructTypeエラーをスローしています。

>>> cnxn = pyodbc.connect(con_string)
>>> aj = cnxn.cursor()
>>>
>>> aj.execute("select * from tjob")
<pyodbc.Cursor object at 0x257b2d0>

>>> row = aj.fetchone()

>>> row
(1127, u'', u'8196660', u'', u'', 0, u'', u'', None, 35, None, 0, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, None, u'', 0, None, None)
>>> rowstr = map(str,row)
>>> rowstr
['1127', '', '8196660', '', '', '0', '', '', 'None', '35', 'None', '0', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', '', '0', 'None', 'None']

>>> schemaString = " ".join([row.column_name for row in aj.columns(table='tjob')])

>>> schemaString
u'ID ExternalID Name Description Notes Type Lot SubLot ParentJobID ProductID PlannedStartDateTime PlannedDurationSeconds Capture01 Capture02 Capture03 Capture04 Capture05 Capture06 Capture07 Capture08 Capture09 Capture10 Capture11 Capture12 Capture13 Capture14 Capture15 Capture16 Capture17 Capture18 Capture19 Capture20 User UserState ModifiedDateTime UploadedDateTime'

>>> fields = [StructField(field_name, StringType(), True) for field_name in schemaString.split()]
>>> schema = StructType(fields)

>>> [f.dataType for f in schema.fields]
[StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType, StringType]

>>> myrdd = sc.parallelize(rowstr)

>>> myrdd.collect()
['1127', '', '8196660', '', '', '0', '', '', 'None', '35', 'None', '0', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', 'None', '', '0', 'None', 'None']

>>> schemaPeople = sqlContext.createDataFrame(myrdd, schema)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/apps/opt/cloudera/parcels/CDH-5.5.2-1.cdh5.5.2.p0.4/lib/spark/python/pyspark/sql/context.py", line 404, in createDataFrame
    rdd, schema = self._createFromRDD(data, schema, samplingRatio)
  File "/apps/opt/cloudera/parcels/CDH-5.5.2-1.cdh5.5.2.p0.4/lib/spark/python/pyspark/sql/context.py", line 298, in _createFromRDD
    _verify_type(row, schema)
  File "/apps/opt/cloudera/parcels/CDH-5.5.2-1.cdh5.5.2.p0.4/lib/spark/python/pyspark/sql/types.py", line 1132, in _verify_type
    raise TypeError("StructType can not accept object in type %s" % type(obj))
TypeError: StructType can not accept object in type <type 'str'>
pythonapache-sparkapache-spark-sqlspark-dataframe
8
ThirdEye

エラーメッセージの理由は次のとおりです。

>>> rowstr
['1127', '', '8196660', '', '', '0', '', '', 'None' ... ]   
#rowstr is a list of str

>>> myrdd = sc.parallelize(rowstr)
#myrdd is a rdd of str

>>> schema = StructType(fields)
#schema is StructType([StringType, StringType, ....])

>>> schemaPeople = sqlContext.createDataFrame(myrdd, schema)
#myrdd should have been RDD([StringType, StringType,...]) but is RDD(str)

これを修正するには、RDDを適切なタイプにします。

>>> myrdd = sc.parallelize([rowstr])
12
Shyamendra Solanki