hezuojiao opened a new pull request #32417:
URL: https://github.com/apache/spark/pull/32417
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### What changes were proposed in this pull request?
This patch proposes to make CatalogString contains nullable information to
help understand Casting failure message.
### Why are the changes needed?
When trying to cast ArrayType/MapType/StructType from containing NULL to not
contain NULL, we will get a confusing failure message.
Here's a example:
```scala
test("array casting") {
val arrayContainsNull = Literal.create(Seq("contains", "null", null),
ArrayType(StringType, containsNull = true))
val ret = cast(arrayContainsNull, ArrayType(StringType, containsNull =
false))
assert(ret.resolved === false)
println(ret.typeCheckFailureMessage)
}
```
Failure massage:
```
cannot cast array<string> to array<string>
```
From the above error message, it is not clear why the error is reported,
because the data type before and after is the same.
Therefore, we need to specify nullable info for
ArrayType/MapType?/StructType in the Catalog String to identify the reason for
Casting Failures.
Failure massage after this patch:
```
cannot cast array<string(nullable=true)> to array<string(nullable=false)>
```
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
New UT
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