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https://issues.apache.org/jira/browse/FLINK-6097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15930087#comment-15930087
]
ASF GitHub Bot commented on FLINK-6097:
---------------------------------------
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.
> Guaranteed the order of the extracted field references
> ------------------------------------------------------
>
> Key: FLINK-6097
> URL: https://issues.apache.org/jira/browse/FLINK-6097
> Project: Flink
> Issue Type: Improvement
> Components: Table API & SQL
> Reporter: sunjincheng
> Assignee: sunjincheng
>
> The current `ProjectionTranslator # identifyFieldReferences` method uses the`
> Set` temporary save field, when the number of elements in the Set is less
> than 5, the Set takes the Se1, Se2, Se3, Se4 data structures. When the number
> of elements is greater than or equal to 5, the Set takes HashSet #
> HashTrieSet and which will cause the data to be out of order. although the
> out of order is also working, but I think the order is better than out of
> order. So I want to improve it,Orderly extraction field.i.e.Guaranteed the
> order of the extracted field references as input order.
> e.g.:
> Add the following elements in turn:
> {code}
> A, b, c, d, e
> Set (a)
> Class scala.collection.immutable.Set $ Set1
> Set (a, b)
> Class scala.collection.immutable.Set $ Set2
> Set (a, b, c)
> Class scala.collection.immutable.Set $ Set3
> Set (a, b, c, d)
> Class scala.collection.immutable.Set $ Set4
> Set (e, a, b, c, d) -> I want (a, b, c, d, e)
> Class scala.collection.immutable.HashSet $ HashTrieSet
> {code}
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