Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/18412#discussion_r124062223
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
---
@@ -482,15 +482,15 @@ case class Cast(child: Expression, dataType:
DataType, timeZoneId: Option[String
case (fromField, toField) => cast(fromField.dataType,
toField.dataType)
}
// TODO: Could be faster?
- val newRow = new GenericInternalRow(from.fields.length)
buildCast[InternalRow](_, row => {
+ val newRow = new GenericInternalRow(from.fields.length)
var i = 0
while (i < row.numFields) {
newRow.update(i,
if (row.isNullAt(i)) null else castFuncs(i)(row.get(i,
from.apply(i).dataType)))
i += 1
}
- newRow.copy()
--- End diff --
@hvanhovell I found the semantics of the original
`GenericMutableRow.copy()` pretty dangerous since it didn't properly implement
deep copy semantics. In fact, it's impossible to do a proper deep copy there.
We only copy the underlying field array but may still share field objects
accidentally.
If we do want to "fix" `GenericInternalRow.copy()`, I'd prefer throwing an
exception instead of following the old `GenericMutableRow.copy()` method.
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