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https://issues.apache.org/jira/browse/FLINK-6097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15930874#comment-15930874
]
ASF GitHub Bot commented on FLINK-6097:
---------------------------------------
Github user sunjincheng121 commented on a diff in the pull request:
https://github.com/apache/flink/pull/3560#discussion_r106761581
--- 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 --
Can you explain more about ` 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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