Jungtaek Lim created FLINK-9742:
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Summary: Widen scope of Expression.resultType to 'public'
Key: FLINK-9742
URL: https://issues.apache.org/jira/browse/FLINK-9742
Project: Flink
Issue Type: Improvement
Components: Table API & SQL
Affects Versions: 1.5.0
Reporter: Jungtaek Lim
I have use case of TableSource which requires custom implementation of
TimestampExtractor. To ensure new TimestampExtractor to cover more general use
cases, accessing Expression.resultType is necessary, but its scope is now
defined as package private for "org.apache.flink".
Below is the implementation of custom TimestampExtractor which leverages
Expression.resultType, hence had to place it to org.apache.flink package (looks
like a hack).
{code:java}
class IsoDateStringAwareExistingField(val field: String) extends
TimestampExtractor {
override def getArgumentFields: Array[String] = Array(field)
override def validateArgumentFields(argumentFieldTypes:
Array[TypeInformation[_]]): Unit = {
val fieldType = argumentFieldTypes(0)
fieldType match {
case Types.LONG => // OK
case Types.SQL_TIMESTAMP => // OK
case Types.STRING => // OK
case _: TypeInformation[_] =>
throw ValidationException(
s"Field '$field' must be of type Long or Timestamp or String but is
of type $fieldType.")
}
}
override def getExpression(fieldAccesses: Array[ResolvedFieldReference]):
Expression = {
val fieldAccess: Expression = fieldAccesses(0)
fieldAccess.resultType match {
case Types.LONG =>
// access LONG field
fieldAccess
case Types.SQL_TIMESTAMP =>
// cast timestamp to long
Cast(fieldAccess, Types.LONG)
case Types.STRING =>
Cast(Cast(fieldAccess, SqlTimeTypeInfo.TIMESTAMP), Types.LONG)
}
}
}{code}
It would be better to just make Expression.resultType public to cover other
cases as well. (I'm not sure other methods would be also better to be public as
well.)
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