[jira] [Updated] (SPARK-33184) spark doesn't read data source column if it is used as an index to an array under a struct

["colin fang (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-33184?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

colin fang updated SPARK-33184:
-------------------------------
    Summary: spark doesn't read data source column if it is used as an index to an array under a struct  (was: spark doesn't read data source column if it is needed as an index to an array in a nested struct)

> spark doesn't read data source column if it is used as an index to an array under a struct
> ------------------------------------------------------------------------------------------
>
>                 Key: SPARK-33184
>                 URL: https://issues.apache.org/jira/browse/SPARK-33184
>             Project: Spark
>          Issue Type: Improvement
>          Components: Spark Core
>    Affects Versions: 3.0.0
>            Reporter: colin fang
>            Priority: Minor
>
> {code:python}
> df = spark.createDataFrame([[1, [[1, 2]]]], schema='x:int,y:struct<a:array<int>>')
> df.write.mode('overwrite').parquet('test')
> {code}
> {code:python}
> # This causes an error "Caused by: java.lang.RuntimeException: Couldn't find x#720 in [y#721]"
> spark.read.parquet('test').select(F.expr('y.a[x]')).show()
> # Explain works fine, note it doesn't read x in ReadSchema
> spark.read.parquet('test').select(F.expr('y.a[x]')).explain()
> == Physical Plan ==
> *(1) !Project [y#713.a[x#712] AS y.a AS `a`[x]#717]
> +- FileScan parquet [y#713] Batched: false, DataFilters: [], Format: Parquet, Location: InMemoryFileIndex, PartitionFilters: [], PushedFilters: [], ReadSchema: struct<y:struct<a:array<int>>>
> {code}
> The code works well if I 
> {code:python}
> # manually select the column it misses
> spark.read.parquet('test').select(F.expr('y.a[x]'), F.col('x')).show()
> # use element_at function
> spark.read.parquet('test').select(F.element_at('y.a', F.col('x') + 1)).show()
> {code}



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