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[SPARK-28706][SQL] Allow cast null type to any types #25425

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jiangxb1987 wants to merge 2 commits into from
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[SPARK-28706][SQL] Allow cast null type to any types #25425

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jiangxb1987 Aug 13, 2019
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jiangxb1987 Aug 13, 2019
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1 change: 1 addition & 0 deletions sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
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Expand Up @@ -134,6 +134,7 @@ object Cast {
case (DateType, TimestampType) => true
case (_: AtomicType, StringType) => true
case (_: CalendarIntervalType, StringType) => true
case (NullType, StringType) => true

@dongjoon-hyun dongjoon-hyun Aug 13, 2019

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So this is a logical partial recover of the previous code case (_, StringType) => true before #25242, right?

@cloud-fan cloud-fan Aug 13, 2019

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I think we can cast null type to any type, how about case (NullType, _) => true?

@dongjoon-hyun dongjoon-hyun Aug 13, 2019

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+1, @cloud-fan 's comment.

In that case, let's create a new JIRA instead of FOLLOWUP, @jiangxb1987 .

@gengliangwang gengliangwang Aug 13, 2019

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+1, @cloud-fan 's comment.


// Spark supports casting between long and timestamp, please see `longToTimestamp` and
// `timestampToLong` for details.
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2 changes: 2 additions & 0 deletions sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastSuite.scala
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Expand Up @@ -1008,6 +1008,8 @@ class CastSuite extends SparkFunSuite with ExpressionEvalHelper {
assert(!Cast.canUpCast(complexType, StringType))
}
}

assert(Cast.canUpCast(NullType, StringType))
}

test("SPARK-27671: cast from nested null type in struct") {
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