[GitHub] [flink] swuferhong commented on a diff in pull request #21490: [FLINK-30368][table-planner] Fix calcite method RelMdUtil$numDistinctVals() wrongly return zero if the method input domainSize much larger than numSelected

[GitBox <gi...@apache.org>]

swuferhong commented on code in PR #21490:
URL: https://github.com/apache/flink/pull/21490#discussion_r1057401207


##########
flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/plan/utils/FlinkRelMdUtil.scala:
##########
@@ -247,6 +248,77 @@ object FlinkRelMdUtil {
     RexUtil.composeConjunction(rexBuilder, pushable, true)
   }
 
+  /**
+   * This method is copied from calcite RelMdUtil. This method should be removed once CALCITE-4351
+   * is fixed. See CALCITE-4351 and FLINK-19780.
+   *
+   * Computes the number of distinct rows for a set of keys returned from a join. Also known as NDV
+   * (number of distinct values).
+   *
+   * @param joinRel
+   *   RelNode representing the join
+   * @param joinType
+   *   type of join
+   * @param groupKey
+   *   keys that the distinct row count will be computed for
+   * @param predicate
+   *   join predicate
+   * @param useMaxNdv
+   *   If true use formula <code>max(left NDV, right NDV)</code>, otherwise use <code>left NDV *
+   *   right NDV</code>.
+   * @return
+   *   number of distinct rows
+   */
+  def getJoinDistinctRowCount(
+      mq: RelMetadataQuery,
+      joinRel: RelNode,
+      joinType: JoinRelType,
+      groupKey: ImmutableBitSet,
+      predicate: RexNode,
+      useMaxNdv: Boolean): Double = {
+    if ((predicate == null || predicate.isAlwaysTrue) && groupKey.isEmpty) return 1d

Review Comment:
   > please format the copied code
   
   Done!



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