chenhao-db commented on PR #47796:
URL: https://github.com/apache/spark/pull/47796#issuecomment-2299989882
In `select
xpath('<a><b>b1</b><b>b2</b><b>b3</b><c>c1</c><c>c2</c></a>','a/b');`, the
Spark results before and after the change are the same: `[null,null,null]`. The
change only marks the return type correctly, but doesn't change the return
value.
However, in `select coalesce(xpath(repeat('<a></a>', id), 'a')[0], '') from
range(1, 2)`, the query would fail with an NPE in generated code before the
change, like:
```
Caused by: java.lang.NullPointerException
at
org.apache.spark.sql.catalyst.expressions.codegen.UnsafeWriter.write(UnsafeWriter.java:110)
at
org.apache.spark.sql.catalyst.expressions.GeneratedClass$SpecificUnsafeProjection.apply(Unknown
Source)
at
org.apache.spark.sql.catalyst.expressions.GeneratedClass$SpecificUnsafeProjection.apply(Unknown
Source)
at scala.collection.Iterator$$anon$10.next(Iterator.scala:461)
...
```
But will return an empty string after the change.
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