Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/23042#discussion_r234401696
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
---
@@ -138,6 +138,11 @@ object TypeCoercion {
case (DateType, TimestampType)
=> if (conf.compareDateTimestampInTimestamp) Some(TimestampType)
else Some(StringType)
+ // to support a popular use case of tables using Decimal(X, 0) for
long IDs instead of strings
+ // see SPARK-26070 for more details
+ case (n: DecimalType, s: StringType) if n.scale == 0 =>
Some(DecimalType(n.precision, n.scale))
--- End diff --
> no implicit cast at all
Is that too strict? I feel it's OK to compare an int with long. Maybe we
should come up with a list of "definitely safe" type coercions, and allow them
only.
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