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

colin fang updated SPARK-33184:
-------------------------------
    Description: 
{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 

- manually select the column it misses 
`spark.read.parquet('test').select(F.expr('y.a[x]'), F.col('x')).show()` 
- or use `F.element_at` function 
`spark.read.parquet('test').select(F.element_at('y.a', F.col('x') + 1)).show()`



  was:
```
df = spark.createDataFrame([[1, [[1, 2]]]], 
schema='x:int,y:struct<a:array<int>>')
df.write.mode('overwrite').parquet('test')
```

```
# 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>>>

```


The code works well if I 

- manually select the column it misses 
`spark.read.parquet('test').select(F.expr('y.a[x]'), F.col('x')).show()` 
- or use `F.element_at` function 
`spark.read.parquet('test').select(F.element_at('y.a', F.col('x') + 1)).show()`



```


> spark doesn't read data source column if it is needed as an index to an array 
> in a nested 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 
> - manually select the column it misses 
> `spark.read.parquet('test').select(F.expr('y.a[x]'), F.col('x')).show()` 
> - or use `F.element_at` function 
> `spark.read.parquet('test').select(F.element_at('y.a', F.col('x') + 
> 1)).show()`



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