From e306c82732eb09e55b4cc7693f4edda520310278 Mon Sep 17 00:00:00 2001
From: Thomas Rebele <thomas.rebele@gmail.com>
Date: Fri, 26 Jun 2026 10:26:15 +0200
Subject: [PATCH] HIVE-29688: HiveRelDecorrelator does not support semi-joins
 with correlation variables only in LHS

---
 .../calcite/rules/HiveRelDecorrelator.java    | 23 ++++++---
 .../clientpositive/decorrelate-semi-join.q    | 17 +++++++
 .../llap/decorrelate-semi-join.q.out          | 51 +++++++++++++++++++
 3 files changed, 84 insertions(+), 7 deletions(-)
 create mode 100644 ql/src/test/queries/clientpositive/decorrelate-semi-join.q
 create mode 100644 ql/src/test/results/clientpositive/llap/decorrelate-semi-join.q.out

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java b/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java
index 7769191e5d8a..9c83c3894a55 100644
--- a/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java
+++ b/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java
@@ -1353,7 +1353,7 @@ public Frame decorrelateRel(Join rel) {
       throw new UnsupportedOperationException("Correlated subqueries in outer join conditions not supported yet." +
         " Join condition: " + rel.getCondition());
     }
-    if (!rel.getJoinType().projectsRight()) {
+    if (JoinRelType.ANTI.equals(rel.getJoinType())) {
       return decorrelateRel((RelNode) rel);
     }
     //
@@ -1374,6 +1374,11 @@ public Frame decorrelateRel(Join rel) {
       return null;
     }
 
+    if (rel.getJoinType().projectsRight() && !rightFrame.corDefOutputs.isEmpty()) {
+      // decorrelating semi-join with correlation variables in the RHS is not supported yet
+      return null;
+    }
+
     final RelNode newJoin = HiveJoin.getJoin(rel.getCluster(), leftFrame.r, rightFrame.r,
         decorrelateExpr(rel.getCondition()), rel.getJoinType());
 
@@ -1385,16 +1390,20 @@ public Frame decorrelateRel(Join rel) {
     int newLeftFieldCount = leftFrame.r.getRowType().getFieldCount();
 
     int oldRightFieldCount = oldRight.getRowType().getFieldCount();
-    assert rel.getRowType().getFieldCount()
-            == oldLeftFieldCount + oldRightFieldCount;
+
+    int expectedRowCount = oldLeftFieldCount + (rel.getJoinType().projectsRight() ? oldRightFieldCount : 0);
+    if (rel.getRowType().getFieldCount() != expectedRowCount)
+      throw new AssertionError();
 
     // Left input positions are not changed.
     mapOldToNewOutputs.putAll(leftFrame.oldToNewOutputs);
 
-    // Right input positions are shifted by newLeftFieldCount.
-    for (int i = 0; i < oldRightFieldCount; i++) {
-      mapOldToNewOutputs.put(i + oldLeftFieldCount,
-              rightFrame.oldToNewOutputs.get(i) + newLeftFieldCount);
+    if (rel.getJoinType().projectsRight()) {
+      // Right input positions are shifted by newLeftFieldCount.
+      for (int i = 0; i < oldRightFieldCount; i++) {
+        mapOldToNewOutputs.put(i + oldLeftFieldCount,
+            rightFrame.oldToNewOutputs.get(i) + newLeftFieldCount);
+      }
     }
 
     final SortedMap<CorDef, Integer> corDefOutputs =
diff --git a/ql/src/test/queries/clientpositive/decorrelate-semi-join.q b/ql/src/test/queries/clientpositive/decorrelate-semi-join.q
new file mode 100644
index 000000000000..d4069f0fdf86
--- /dev/null
+++ b/ql/src/test/queries/clientpositive/decorrelate-semi-join.q
@@ -0,0 +1,17 @@
+DROP TABLE IF EXISTS `tab`;
+CREATE EXTERNAL TABLE `tab`(
+  `f1` string,
+  `f2` string,
+  `f3` string,
+  `f4` string,
+  `f5` string,
+  `f6` string);
+
+SELECT 1
+FROM tab a
+WHERE a.f4 IN ('1', '2')
+AND EXISTS (
+  SELECT 1
+  FROM tab b
+  WHERE  a.f6 = b.f1 AND b.f3 IN (SELECT 1)
+);
diff --git a/ql/src/test/results/clientpositive/llap/decorrelate-semi-join.q.out b/ql/src/test/results/clientpositive/llap/decorrelate-semi-join.q.out
new file mode 100644
index 000000000000..3f21b9c24ea9
--- /dev/null
+++ b/ql/src/test/results/clientpositive/llap/decorrelate-semi-join.q.out
@@ -0,0 +1,51 @@
+PREHOOK: query: DROP TABLE IF EXISTS `tab`
+PREHOOK: type: DROPTABLE
+PREHOOK: Output: database:default
+POSTHOOK: query: DROP TABLE IF EXISTS `tab`
+POSTHOOK: type: DROPTABLE
+POSTHOOK: Output: database:default
+PREHOOK: query: CREATE EXTERNAL TABLE `tab`(
+  `f1` string,
+  `f2` string,
+  `f3` string,
+  `f4` string,
+  `f5` string,
+  `f6` string)
+PREHOOK: type: CREATETABLE
+PREHOOK: Output: database:default
+PREHOOK: Output: default@tab
+POSTHOOK: query: CREATE EXTERNAL TABLE `tab`(
+  `f1` string,
+  `f2` string,
+  `f3` string,
+  `f4` string,
+  `f5` string,
+  `f6` string)
+POSTHOOK: type: CREATETABLE
+POSTHOOK: Output: database:default
+POSTHOOK: Output: default@tab
+Warning: Shuffle Join MERGEJOIN[29][tables = [$hdt$_1, $hdt$_2]] in Stage 'Reducer 2' is a cross product
+PREHOOK: query: SELECT 1
+FROM tab a
+WHERE a.f4 IN ('1', '2')
+AND EXISTS (
+  SELECT 1
+  FROM tab b
+  WHERE  a.f6 = b.f1 AND b.f3 IN (SELECT 1)
+)
+PREHOOK: type: QUERY
+PREHOOK: Input: _dummy_database@_dummy_table
+PREHOOK: Input: default@tab
+#### A masked pattern was here ####
+POSTHOOK: query: SELECT 1
+FROM tab a
+WHERE a.f4 IN ('1', '2')
+AND EXISTS (
+  SELECT 1
+  FROM tab b
+  WHERE  a.f6 = b.f1 AND b.f3 IN (SELECT 1)
+)
+POSTHOOK: type: QUERY
+POSTHOOK: Input: _dummy_database@_dummy_table
+POSTHOOK: Input: default@tab
+#### A masked pattern was here ####