[GitHub] [flink] lincoln-lil commented on a diff in pull request #20745: [FLINK-28988] Don't push above filters down into the right table for temporal join

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

lincoln-lil commented on code in PR #20745:
URL: https://github.com/apache/flink/pull/20745#discussion_r1021669344


##########
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/FlinkFilterJoinRule.java:
##########
@@ -128,7 +129,9 @@ protected void perform(RelOptRuleCall call, Filter filter, Join join) {
                 joinType,
                 true,
                 !joinType.generatesNullsOnLeft(),
-                !joinType.generatesNullsOnRight(),
+                !joinType.generatesNullsOnRight()
+                        && !TemporalJoinUtil.containsInitialTemporalJoinCondition(

Review Comment:
   the filter added here and line 176 below are not enough to prevent pushing down a filter into the right   side input of event time temporal join, because this rule will also perform pushing both above and join filters to opposite side by transitive rule, e.g., think of such an query:
   
   ```sql
   SELECT *      
   FROM Orders AS o JOIN
   rates_last_row_rowtime FOR SYSTEM_TIME AS OF o.rowtime AS r
   ON o.currency = r.currency AND o.currency = 10
   ```
   though the local predicate 'o.currency = 10' is releated to left side, but by this transitive optimization, it will push a new filter 'r.currency = 10' to the right side, this will break our target, so we need to figure out a way to cover this case



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