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From "Sean Owen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-21392) Unable to infer schema when loading Parquet file
Date Wed, 12 Jul 2017 20:00:03 GMT

    [ https://issues.apache.org/jira/browse/SPARK-21392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16084583#comment-16084583
] 

Sean Owen commented on SPARK-21392:
-----------------------------------

Can you format this so it's readable?
I don't understand how "response" can be what appears to be a column name, but then also a
path to a Parquet file. Are you just mixing up arguments?

> Unable to infer schema when loading Parquet file
> ------------------------------------------------
>
>                 Key: SPARK-21392
>                 URL: https://issues.apache.org/jira/browse/SPARK-21392
>             Project: Spark
>          Issue Type: Bug
>          Components: PySpark
>    Affects Versions: 2.1.1
>         Environment: Spark 2.1.1. python 2.7.6
>            Reporter: Stuart Reynolds
>              Labels: parquet, pyspark
>
> The following boring code works
> {{    response = "mi_or_chd_5"
>     colname = "f_1000"
>     outcome = sqlc.sql("""select eid,{response} as response
>     from outcomes
>     where {response} IS NOT NULL""".format(response=response))
>     outcome.write.parquet(response, mode="overwrite")
>     
>     col = sqlc.sql("""select eid,{colname} as {colname}
>     from baseline_denull
>     where {colname} IS NOT NULL""".format(colname=colname))
>     col.write.parquet(colname, mode="overwrite")
>     >>> print outcome.schema
>     StructType(List(StructField(eid,IntegerType,true),StructField(response,ShortType,true)))
>     >>> print col.schema
>     StructType(List(StructField(eid,IntegerType,true),StructField(f_1000,DoubleType,true)))
> }}.
>     
> But then,
> {{
>     outcome2 = sqlc.read.parquet(response)  # fail
>     col2 = sqlc.read.parquet(colname) # fail
> }}.
> fails with:
> {{    AnalysisException: u'Unable to infer schema for Parquet. It must be specified manually.;'
> }}.
> in 
> {{    /usr/local/lib/python2.7/dist-packages/pyspark-2.1.0+hadoop2.7-py2.7.egg/pyspark/sql/utils.pyc
in deco(*a, **kw)
> }}.
> The documentation for parquet says the format is self describing, and the full schema
was available when the parquet file was saved. What gives?
> Seems related to: https://issues.apache.org/jira/browse/SPARK-16975, but which claims
it was fixed in 2.0.1, 2.1.0. (Current bug is 2.1.1)



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