diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java
index f7cbb9d..02dc6f6 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/subplan/InlineAllNtsInSubplanVisitor.java
@@ -655,7 +655,17 @@
 
     @Override
     public ILogicalOperator visitWindowOperator(WindowOperator op, Void arg) throws AlgebricksException {
-        return visitSingleInputOperator(op);
+        visitSingleInputOperator(op);
+        List<LogicalVariable> partitionByVars = op.getPartitionVarList();
+        for (LogicalVariable keyVar : correlatedKeyVars) {
+            if (!partitionByVars.contains(keyVar)) {
+                VariableReferenceExpression keyVarRef = new VariableReferenceExpression(keyVar);
+                keyVarRef.setSourceLocation(op.getSourceLocation());
+                op.getPartitionExpressions().add(new MutableObject<>(keyVarRef));
+            }
+        }
+        context.computeAndSetTypeEnvironmentForOperator(op);
+        return op;
     }
 
     /**
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815-2.sqlpp b/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815-2.sqlpp
new file mode 100644
index 0000000..74034d6
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815-2.sqlpp
@@ -0,0 +1,42 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+drop dataverse test if exists;
+create dataverse test;
+
+use test;
+
+create type t1 as {
+ _id: uuid
+};
+
+create dataset RawTweet(t1) primary key _id autogenerated;
+
+create dataset Evidence(t1) primary key _id autogenerated;
+
+create dataset Verification(t1) primary key _id autogenerated;
+
+select t.id, array_sort(ranks) ranks
+from RawTweet t
+let ranks = (
+  select value rank() over(order by e.url)
+  from Verification v, v.evidence ve, Evidence e
+  where t.id = v.tweet_id and ve = e.ev_id
+)
+order by t.id;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815-3.sqlpp b/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815-3.sqlpp
new file mode 100644
index 0000000..6b0501e
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/queries/subquery/query-ASTERIXDB-2815-3.sqlpp
@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+drop dataverse test if exists;
+create dataverse test;
+
+use test;
+
+create type t1 as {
+ _id: uuid
+};
+
+create dataset RawTweet(t1) primary key _id autogenerated;
+
+create dataset Evidence(t1) primary key _id autogenerated;
+
+create dataset Verification(t1) primary key _id autogenerated;
+
+select t.id, array_sort(ranks) ranks
+from RawTweet t
+let ranks = (
+  select value rank() over(
+    partition by (tobigint(substring(e.url, -4)) % 2)
+    order by e.url
+  )
+  from Verification v, v.evidence ve, Evidence e
+  where t.id = v.tweet_id and ve = e.ev_id
+)
+order by t.id;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815-2.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815-2.plan
new file mode 100644
index 0000000..897163e
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815-2.plan
@@ -0,0 +1,72 @@
+-- DISTRIBUTE_RESULT  |PARTITIONED|
+  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+    -- STREAM_PROJECT  |PARTITIONED|
+      -- ASSIGN  |PARTITIONED|
+        -- SORT_MERGE_EXCHANGE [$$82(ASC) ]  |PARTITIONED|
+          -- STABLE_SORT [$$82(ASC)]  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+              -- STREAM_PROJECT  |PARTITIONED|
+                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                  -- PRE_CLUSTERED_GROUP_BY[$$78]  |PARTITIONED|
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- STREAM_SELECT  |LOCAL|
+                                -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
+                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                      -- STREAM_PROJECT  |PARTITIONED|
+                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                          -- HYBRID_HASH_JOIN [$$78][$$89]  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- STREAM_PROJECT  |PARTITIONED|
+                                -- ASSIGN  |PARTITIONED|
+                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                    -- REPLICATE  |PARTITIONED|
+                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                        -- STREAM_PROJECT  |PARTITIONED|
+                                          -- ASSIGN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- DATASOURCE_SCAN (test.RawTweet)  |PARTITIONED|
+                                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                  -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- ASSIGN  |PARTITIONED|
+                                -- STREAM_PROJECT  |PARTITIONED|
+                                  -- WINDOW_STREAM  |PARTITIONED|
+                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                      -- STABLE_SORT [$$89(ASC), $$e.url(ASC)]  |PARTITIONED|
+                                        -- HASH_PARTITION_EXCHANGE [$$89]  |PARTITIONED|
+                                          -- STREAM_PROJECT  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- HYBRID_HASH_JOIN [$$ve][$$81]  |PARTITIONED|
+                                                -- HASH_PARTITION_EXCHANGE [$$ve]  |PARTITIONED|
+                                                  -- STREAM_PROJECT  |PARTITIONED|
+                                                    -- UNNEST  |PARTITIONED|
+                                                      -- STREAM_PROJECT  |PARTITIONED|
+                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                          -- HYBRID_HASH_JOIN [$$87][$$83]  |PARTITIONED|
+                                                            -- HASH_PARTITION_EXCHANGE [$$87]  |PARTITIONED|
+                                                              -- REPLICATE  |PARTITIONED|
+                                                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                  -- STREAM_PROJECT  |PARTITIONED|
+                                                                    -- ASSIGN  |PARTITIONED|
+                                                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                        -- DATASOURCE_SCAN (test.RawTweet)  |PARTITIONED|
+                                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                            -- HASH_PARTITION_EXCHANGE [$$83]  |PARTITIONED|
+                                                              -- STREAM_PROJECT  |PARTITIONED|
+                                                                -- ASSIGN  |PARTITIONED|
+                                                                  -- STREAM_PROJECT  |PARTITIONED|
+                                                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                      -- DATASOURCE_SCAN (test.Verification)  |PARTITIONED|
+                                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                -- HASH_PARTITION_EXCHANGE [$$81]  |PARTITIONED|
+                                                  -- STREAM_PROJECT  |PARTITIONED|
+                                                    -- ASSIGN  |PARTITIONED|
+                                                      -- STREAM_PROJECT  |PARTITIONED|
+                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                          -- DATASOURCE_SCAN (test.Evidence)  |PARTITIONED|
+                                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815-3.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815-3.plan
new file mode 100644
index 0000000..6ca6f1c
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/query-ASTERIXDB-2815-3.plan
@@ -0,0 +1,73 @@
+-- DISTRIBUTE_RESULT  |PARTITIONED|
+  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+    -- STREAM_PROJECT  |PARTITIONED|
+      -- ASSIGN  |PARTITIONED|
+        -- SORT_MERGE_EXCHANGE [$$88(ASC) ]  |PARTITIONED|
+          -- STABLE_SORT [$$88(ASC)]  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+              -- STREAM_PROJECT  |PARTITIONED|
+                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                  -- PRE_CLUSTERED_GROUP_BY[$$84]  |PARTITIONED|
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- STREAM_SELECT  |LOCAL|
+                                -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
+                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                      -- STREAM_PROJECT  |PARTITIONED|
+                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                          -- HYBRID_HASH_JOIN [$$84][$$95]  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- STREAM_PROJECT  |PARTITIONED|
+                                -- ASSIGN  |PARTITIONED|
+                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                    -- REPLICATE  |PARTITIONED|
+                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                        -- STREAM_PROJECT  |PARTITIONED|
+                                          -- ASSIGN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- DATASOURCE_SCAN (test.RawTweet)  |PARTITIONED|
+                                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                  -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                            -- HASH_PARTITION_EXCHANGE [$$95]  |PARTITIONED|
+                              -- ASSIGN  |PARTITIONED|
+                                -- STREAM_PROJECT  |PARTITIONED|
+                                  -- WINDOW_STREAM  |PARTITIONED|
+                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                      -- STABLE_SORT [$$72(ASC), $$95(ASC), $$83(ASC)]  |PARTITIONED|
+                                        -- HASH_PARTITION_EXCHANGE [$$72, $$95]  |PARTITIONED|
+                                          -- ASSIGN  |PARTITIONED|
+                                            -- STREAM_PROJECT  |PARTITIONED|
+                                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                -- HYBRID_HASH_JOIN [$$ve][$$87]  |PARTITIONED|
+                                                  -- HASH_PARTITION_EXCHANGE [$$ve]  |PARTITIONED|
+                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                      -- UNNEST  |PARTITIONED|
+                                                        -- STREAM_PROJECT  |PARTITIONED|
+                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                            -- HYBRID_HASH_JOIN [$$93][$$89]  |PARTITIONED|
+                                                              -- HASH_PARTITION_EXCHANGE [$$93]  |PARTITIONED|
+                                                                -- REPLICATE  |PARTITIONED|
+                                                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                                      -- ASSIGN  |PARTITIONED|
+                                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                          -- DATASOURCE_SCAN (test.RawTweet)  |PARTITIONED|
+                                                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                              -- HASH_PARTITION_EXCHANGE [$$89]  |PARTITIONED|
+                                                                -- STREAM_PROJECT  |PARTITIONED|
+                                                                  -- ASSIGN  |PARTITIONED|
+                                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                        -- DATASOURCE_SCAN (test.Verification)  |PARTITIONED|
+                                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                  -- HASH_PARTITION_EXCHANGE [$$87]  |PARTITIONED|
+                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                      -- ASSIGN  |PARTITIONED|
+                                                        -- STREAM_PROJECT  |PARTITIONED|
+                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                            -- DATASOURCE_SCAN (test.Evidence)  |PARTITIONED|
+                                                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                                -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.4.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.4.query.sqlpp
new file mode 100644
index 0000000..d94a669
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.4.query.sqlpp
@@ -0,0 +1,32 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Test decorrelation of window functions
+ */
+
+use test;
+
+select t.id, array_sort(ranks) ranks
+from RawTweet t
+let ranks = (
+  select value rank() over(order by e.url)
+  from Verification v, v.evidence ve, Evidence e
+  where t.id = v.tweet_id and ve = e.ev_id
+)
+order by t.id;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.5.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.5.query.sqlpp
new file mode 100644
index 0000000..3bec7f9
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.5.query.sqlpp
@@ -0,0 +1,35 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Test decorrelation of window functions
+ */
+
+use test;
+
+select t.id, array_sort(ranks) ranks
+from RawTweet t
+let ranks = (
+  select value rank() over(
+    partition by (tobigint(substring(e.url, -4)) % 2)
+    order by e.url
+  )
+  from Verification v, v.evidence ve, Evidence e
+  where t.id = v.tweet_id and ve = e.ev_id
+)
+order by t.id;
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.4.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.4.adm
new file mode 100644
index 0000000..c35bf4e
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.4.adm
@@ -0,0 +1,5 @@
+{ "ranks": [ 1, 2 ], "id": 1 }
+{ "ranks": [ 1, 2, 3, 4 ], "id": 2 }
+{ "ranks": [  ], "id": 3 }
+{ "ranks": [ 1, 2, 3, 4, 5, 6 ], "id": 4 }
+{ "ranks": [ 1 ], "id": 5 }
\ No newline at end of file
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.5.adm b/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.5.adm
new file mode 100644
index 0000000..9ddd8aa
--- /dev/null
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results/subquery/query-ASTERIXDB-2815/query-ASTERIXDB-2815.5.adm
@@ -0,0 +1,5 @@
+{ "ranks": [ 1, 1 ], "id": 1 }
+{ "ranks": [ 1, 1, 2, 2 ], "id": 2 }
+{ "ranks": [  ], "id": 3 }
+{ "ranks": [ 1, 1, 2, 2, 3, 3 ], "id": 4 }
+{ "ranks": [ 1 ], "id": 5 }
\ No newline at end of file