From f62cdecc08bdc6cd3ec691f885034adcaa0706fd Mon Sep 17 00:00:00 2001
From: minghong <englefly@gmail.com>
Date: Fri, 22 Mar 2024 20:53:30 +0800
Subject: [PATCH] [fix](Nereids) do not push down topn-filter through
 right/full outer join if the first orderkey is nulls first (#32633)

* do not push down topn-filter through right/full outer join if the first order key is nulls first
---
 .../nereids/processor/post/TopNScanOpt.java      | 16 +++++++++++++---
 .../nereids_tpch_p0/tpch/topn-filter.groovy      | 15 +++++++++++++++
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopNScanOpt.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopNScanOpt.java
index a9425cb715..63754afe4d 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopNScanOpt.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/processor/post/TopNScanOpt.java
@@ -22,6 +22,7 @@ import org.apache.doris.nereids.trees.expressions.Expression;
 import org.apache.doris.nereids.trees.expressions.SlotReference;
 import org.apache.doris.nereids.trees.plans.Plan;
 import org.apache.doris.nereids.trees.plans.SortPhase;
+import org.apache.doris.nereids.trees.plans.algebra.Join;
 import org.apache.doris.nereids.trees.plans.algebra.OlapScan;
 import org.apache.doris.nereids.trees.plans.physical.PhysicalCatalogRelation;
 import org.apache.doris.nereids.trees.plans.physical.PhysicalDeferMaterializeTopN;
@@ -89,7 +90,9 @@ public class TopNScanOpt extends PlanPostProcessor {
         if (! (firstKey instanceof SlotReference)) {
             return Optional.empty();
         }
-        OlapScan olapScan = findScanNodeBySlotReference(topN, (SlotReference) firstKey);
+
+        boolean nullsFirst = topN.getOrderKeys().get(0).isNullFirst();
+        OlapScan olapScan = findScanNodeBySlotReference(topN, (SlotReference) firstKey, nullsFirst);
         if (olapScan != null
                 && olapScan.getTable().isDupKeysOrMergeOnWrite()
                 && olapScan instanceof PhysicalCatalogRelation) {
@@ -99,7 +102,14 @@ public class TopNScanOpt extends PlanPostProcessor {
         return Optional.empty();
     }
 
-    private OlapScan findScanNodeBySlotReference(Plan root, SlotReference slot) {
+    private OlapScan findScanNodeBySlotReference(Plan root, SlotReference slot, boolean nullsFirst) {
+        // topn-filter cannot be pushed through right/full outer join if the first orderKey is nulls first
+        if (nullsFirst && root instanceof Join) {
+            Join join = (Join) root;
+            if (join.getJoinType().isRightOuterJoin() || join.getJoinType().isFullOuterJoin()) {
+                return null;
+            }
+        }
         OlapScan target = null;
         if (root instanceof OlapScan && root.getOutputSet().contains(slot)) {
             return (OlapScan) root;
@@ -109,7 +119,7 @@ public class TopNScanOpt extends PlanPostProcessor {
                 // TODO for union, topn-filter can be pushed down to all of its children.
                 Plan child = root.child(0);
                 if (!(child instanceof PhysicalWindow) && child.getOutputSet().contains(slot)) {
-                    target = findScanNodeBySlotReference(child, slot);
+                    target = findScanNodeBySlotReference(child, slot, nullsFirst);
                     if (target != null) {
                         return target;
                     }
diff --git a/regression-test/suites/nereids_tpch_p0/tpch/topn-filter.groovy b/regression-test/suites/nereids_tpch_p0/tpch/topn-filter.groovy
index 14733d1303..3a29274a2f 100644
--- a/regression-test/suites/nereids_tpch_p0/tpch/topn-filter.groovy
+++ b/regression-test/suites/nereids_tpch_p0/tpch/topn-filter.groovy
@@ -116,6 +116,21 @@ suite("topn-filter") {
     }
 
     qt_groupingsets "select n_regionkey, sum(n_nationkey) from nation group by grouping sets((n_regionkey)) order by n_regionkey limit 2;"
+    
+    explain {
+        sql "select * from nation right outer join region on r_regionkey = n_regionkey order by n_regionkey nulls first limit 1; "
+        notContains "TOPN OPT:"
+    }
+
+    explain {
+        sql "select * from nation right outer join region on r_regionkey = n_regionkey order by n_regionkey nulls last limit 1; "
+        contains "TOPN OPT:"
+    }
+
+    explain {
+        sql "select * from nation right outer join region on r_regionkey = n_regionkey order by n_regionkey nulls last, n_name nulls first limit 1; "
+        contains "TOPN OPT:"
+    }
 
     sql "set enable_pipeline_engine=false;"
     sql "set enable_pipeline_x_engine=false;"