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Posted to issues@flink.apache.org by "swuferhong (via GitHub)" <gi...@apache.org> on 2023/03/01 07:37:13 UTC

[GitHub] [flink] swuferhong opened a new pull request, #22049: [FLINK-31273][table-planner] Fix left join with IS_NULL filter be wrongly pushed down and get wrong join results

swuferhong opened a new pull request, #22049:
URL: https://github.com/apache/flink/pull/22049

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   ## What is the purpose of the change
   
   This pr is aims to fix left join with IS_NULL filter be wrongly pushed down and get wrong join results. The example case is:
   `SELECT * FROM MyTable1 LEFT JOIN MyTable2 ON a1 = a2 WHERE a2 IS NULL AND a1 < 10`. For this query, the planner will get a wrong plan:
   
   `LogicalProject(a1=[$0], b1=[$1], c1=[$2], b2=[$3], c2=[$4], a2=[$5])
   +- LogicalFilter(condition=[IS NULL($5)])
      +- LogicalJoin(condition=[=($0, $5)], joinType=[left])
         :- LogicalValues(tuples=[[]])
         +- LogicalTableScan(table=[[default_catalog, default_database, MyTable2]]) `
   
   For this case, even if there is a filter  `a2 IS NULL`, the `a1 IS NULL` cannot be generated for left join by rule `FlinkFilterJoinRule` and this filter cannot be pushed down to both MyTable1 and MyTable2.
   
   ## Brief change log
   
   - Change rule `FlinkFilterJoinRule`
   - Adding UT and IT
   
   
   ## Verifying this change
   
   - Adding UT and IT
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): no
     - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: no
     - The serializers: no
     - The runtime per-record code paths (performance sensitive): no
     - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper:  no
     - The S3 file system connector: no
   
   ## Documentation
   
     - Does this pull request introduce a new feature? no
     - If yes, how is the feature documented? no docs
   


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[GitHub] [flink] godfreyhe commented on a diff in pull request #22049: [FLINK-31273][table-planner] Fix left join with IS_NULL filter be wrongly pushed down and get wrong join results

Posted by "godfreyhe (via GitHub)" <gi...@apache.org>.

godfreyhe commented on code in PR #22049:
URL: https://github.com/apache/flink/pull/22049#discussion_r1135047849


##########
flink-table/flink-table-planner/src/test/resources/org/apache/flink/table/planner/plan/batch/sql/MultipleInputCreationTest.xml:
##########
@@ -136,11 +136,9 @@ LogicalProject(a=[$0], d=[$1], e=[$2], f=[$3], ny=[$4], a0=[$5], b=[$6], c=[$7])
       <![CDATA[
 MultipleInput(readOrder=[0,0,1], members=[\nNestedLoopJoin(joinType=[LeftOuterJoin], where=[(a = a0)], select=[a, d, e, f, ny, a0, b, c], build=[right])\n:- NestedLoopJoin(joinType=[LeftOuterJoin], where=[(a = d)], select=[a, d, e, f, ny], build=[right])\n:  :- Calc(select=[a], where=[(a > 10)])\n:  :  +- [#3] BoundedStreamScan(table=[[default_catalog, default_database, chainable]], fields=[a])\n:  +- [#2] Exchange(distribution=[broadcast])\n+- [#1] Exchange(distribution=[broadcast])\n])
 :- Exchange(distribution=[broadcast])
-:  +- Calc(select=[a, b, c], where=[(a > 10)])

Review Comment:
   why the left side filters can not be pushed down ?



##########
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/FlinkFilterJoinRule.java:
##########
@@ -386,6 +387,21 @@ private void pushFiltersToAnotherSide(
         }
     }
 
+    private boolean isSuitableFilterToPush(RexNode filter, JoinRelType joinType) {
+        if (filter.isAlwaysTrue()) {
+            return false;
+        }
+        // For left/right outer join, we cannot push down IS_NULL filter to other side. Take left
+        // outer join as an example, If the join right side contains an IS_NULL filter, while we try
+        // to push it to the join left side and the left side have any other filter on this column,
+        // which will conflict and generate wrong plan.
+        if ((joinType == JoinRelType.LEFT || joinType == JoinRelType.RIGHT)

Review Comment:
   please also take care about `a2 = null`



##########
flink-table/flink-table-planner/src/test/java/org/apache/flink/table/planner/plan/rules/logical/FlinkFilterJoinRuleTest.java:
##########
@@ -240,6 +240,21 @@ public void testLeftJoinWithAllFiltersFromWhere() {
                 "SELECT * FROM MyTable1 LEFT JOIN MyTable2 ON true WHERE b1 = b2 AND c1 = c2 AND a2 = 2 AND b2 > 10 AND COALESCE(c1, c2) <> '' ");
     }
 
+    @Test

Review Comment:
   please add some tests (including IT case) for inner joins



##########
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/FlinkFilterJoinRule.java:
##########
@@ -386,6 +387,21 @@ private void pushFiltersToAnotherSide(
         }
     }
 
+    private boolean isSuitableFilterToPush(RexNode filter, JoinRelType joinType) {
+        if (filter.isAlwaysTrue()) {
+            return false;
+        }
+        // For left/right outer join, we cannot push down IS_NULL filter to other side. Take left
+        // outer join as an example, If the join right side contains an IS_NULL filter, while we try
+        // to push it to the join left side and the left side have any other filter on this column,
+        // which will conflict and generate wrong plan.
+        if ((joinType == JoinRelType.LEFT || joinType == JoinRelType.RIGHT)

Review Comment:
   additional, less(or equal) than, greater (or equal) than  a literal can also be supported



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[GitHub] [flink] godfreyhe commented on a diff in pull request #22049: [FLINK-31273][table-planner] Fix left join with IS_NULL filter be wrongly pushed down and get wrong join results

Posted by "godfreyhe (via GitHub)" <gi...@apache.org>.

godfreyhe commented on code in PR #22049:
URL: https://github.com/apache/flink/pull/22049#discussion_r1134883506


##########
flink-table/flink-table-planner/src/main/java/org/apache/flink/table/planner/plan/rules/logical/FlinkFilterJoinRule.java:
##########
@@ -386,6 +387,21 @@ private void pushFiltersToAnotherSide(
         }
     }
 
+    private boolean isSuitableFilterToPush(RexNode filter, JoinRelType joinType) {
+        if (filter.isAlwaysTrue()) {
+            return false;
+        }
+        // For left/right outer join, we cannot push down IS_NULL filter to other side. Take left
+        // outer join as an example, If the join right side contains an IS_NULL filter, while we try
+        // to push it to the join left side and the left side have any other filter on this column,
+        // which will conflict and generate wrong plan.
+        if ((joinType == JoinRelType.LEFT || joinType == JoinRelType.RIGHT)

Review Comment:
   for left outer join, only the equal conditions from right side can be push to the left side. and vice versa for right outer join.
   
   please add some non equal conditions (such as a2 <> 10 ) in the IT case



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