sarutak opened a new pull request #33106:
URL: https://github.com/apache/spark/pull/33106
### What changes were proposed in this pull request?
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This PR fixes an issue that field names of structs generated by `arrays_zip`
function could be unexpectedly re-written by analyzer/optimizer.
Here is an example.
```
val df = sc.parallelize(Seq((Array(1, 2), Array(3, 4)))).toDF("a1",
"b1").selectExpr("arrays_zip(a1, b1) as zipped")
df.printSchema
root
|-- zipped: array (nullable = true)
| |-- element: struct (containsNull = false)
| | |-- a1: integer (nullable = true)
// OK. a1 is expected name
| | |-- b1: integer (nullable = true)
// OK. b1 is expected name
df.explain
== Physical Plan ==
*(1) Project [arrays_zip(_1#3, _2#4) AS zipped#12] // Not OK.
field names are re-written as _1 and _2 respectively
df.write.parquet("/tmp/test.parquet")
val df2 = spark.read.parquet("/tmp/test.parquet")
df2.printSchema
root
|-- zipped: array (nullable = true)
| |-- element: struct (containsNull = true)
| | |-- _1: integer (nullable = true)
// Not OK. a1 is expected but got _1
| | |-- _2: integer (nullable = true)
// Not OK. b1 is expected but got _2
```
This issue happens when `AliasHelper.replaceAliasButKeepName` or
`AliasHelper.trimNonTopLevelAliases` called via analyzer/optimizer is applied.
https://github.com/apache/spark/blob/b89cd8d75a0e78c6953cdd21c6e9c41495ed018f/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala#L883
https://github.com/apache/spark/blob/b89cd8d75a0e78c6953cdd21c6e9c41495ed018f/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala#L3759
I investigated functions which can be affected this issue but I found only
`arrays_zip` so far.
To fix this issue, this PR changes the definition of `ArraysZip` to retain
field names to avoid being re-written by analyzer/optimizer.
### Why are the changes needed?
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This is apparently a bug.
### Does this PR introduce _any_ user-facing change?
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the documentation fix.
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No. After this change, the field names are no longer re-written but it
should be expected behavior for users.
### How was this patch tested?
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New tests.
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