Github user KurtYoung commented on a diff in the pull request:
https://github.com/apache/flink/pull/3560#discussion_r106669352
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/ProjectionTranslator.scala
---
@@ -227,18 +227,23 @@ object ProjectionTranslator {
* @param exprs a list of expressions to extract
* @return a list of field references extracted from the given
expressions
*/
- def extractFieldReferences(exprs: Seq[Expression]): Seq[NamedExpression]
= {
- exprs.foldLeft(Set[NamedExpression]()) {
+ def extractFieldReferences(exprs: Seq[Expression]):
List[NamedExpression] = {
+ exprs.foldLeft(List[NamedExpression]()) {
(fieldReferences, expr) => identifyFieldReferences(expr,
fieldReferences)
- }.toSeq
+ }
}
private def identifyFieldReferences(
expr: Expression,
- fieldReferences: Set[NamedExpression]): Set[NamedExpression] = expr
match {
+ fieldReferences: List[NamedExpression]): List[NamedExpression] =
expr match {
--- End diff --
I think using Set here gave us better intuition that we actually want to
count uniq fields, any reason why you want to keep the order? Especially the
order is not defined very well, it will change easily if we modify the code.
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