diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/aggregate/constant-gby-agg.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/aggregate/constant-gby-agg.plan
index 773be15..94bf390 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/aggregate/constant-gby-agg.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/aggregate/constant-gby-agg.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$26]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$26]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$26(ASC)] HASH:[$$26]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$26]  |PARTITIONED|
               -- SORT_GROUP_BY[$$22]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/consolidate-selects-complex.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/consolidate-selects-complex.plan
index 3abde90..aa8c7e6 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/consolidate-selects-complex.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/consolidate-selects-complex.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/count-tweets.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/count-tweets.plan
index 5db2633..a17020e 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/count-tweets.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/count-tweets.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$14]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$14]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$14(ASC)] HASH:[$$14]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$14]  |PARTITIONED|
               -- SORT_GROUP_BY[$$4]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/fj-phase1.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/fj-phase1.plan
index 64c0b06..83af511 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/fj-phase1.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/fj-phase1.plan
@@ -31,12 +31,12 @@
                                 -- SORT_MERGE_EXCHANGE [$$23(DESC) ]  |PARTITIONED|
                                   -- STABLE_SORT [$$23(DESC)]  |PARTITIONED|
                                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                      -- PRE_CLUSTERED_GROUP_BY[$$30]  |PARTITIONED|
+                                      -- SORT_GROUP_BY[$$30]  |PARTITIONED|
                                               {
                                                 -- AGGREGATE  |LOCAL|
                                                   -- NESTED_TUPLE_SOURCE  |LOCAL|
                                               }
-                                        -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$30(ASC)] HASH:[$$30]  |PARTITIONED|
+                                        -- HASH_PARTITION_EXCHANGE [$$30]  |PARTITIONED|
                                           -- SORT_GROUP_BY[$$3]  |PARTITIONED|
                                                   {
                                                     -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/inlined_q18_large_volume_customer.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/inlined_q18_large_volume_customer.plan
index f438fac..b2d5267 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/inlined_q18_large_volume_customer.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/inlined_q18_large_volume_customer.plan
@@ -8,12 +8,12 @@
               -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                 -- STABLE_SORT [topK: 100] [$$12(DESC), $$11(ASC)]  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- PRE_CLUSTERED_GROUP_BY[$$72, $$73]  |PARTITIONED|
+                    -- SORT_GROUP_BY[$$72, $$73]  |PARTITIONED|
                             {
                               -- AGGREGATE  |LOCAL|
                                 -- NESTED_TUPLE_SOURCE  |LOCAL|
                             }
-                      -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$72(ASC), $$73(ASC)] HASH:[$$72, $$73]  |PARTITIONED|
+                      -- HASH_PARTITION_EXCHANGE [$$72, $$73]  |PARTITIONED|
                         -- SORT_GROUP_BY[$$56, $$57]  |PARTITIONED|
                                 {
                                   -- AGGREGATE  |LOCAL|
@@ -49,12 +49,12 @@
                                             -- STREAM_PROJECT  |PARTITIONED|
                                               -- STREAM_SELECT  |PARTITIONED|
                                                 -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                  -- PRE_CLUSTERED_GROUP_BY[$$69]  |PARTITIONED|
+                                                  -- SORT_GROUP_BY[$$69]  |PARTITIONED|
                                                           {
                                                             -- AGGREGATE  |LOCAL|
                                                               -- NESTED_TUPLE_SOURCE  |LOCAL|
                                                           }
-                                                    -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$69(ASC)] HASH:[$$69]  |PARTITIONED|
+                                                    -- HASH_PARTITION_EXCHANGE [$$69]  |PARTITIONED|
                                                       -- PRE_CLUSTERED_GROUP_BY[$$58]  |PARTITIONED|
                                                               {
                                                                 -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-aggreg.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-aggreg.plan
index c100a31..45b584a 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-aggreg.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-aggreg.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$24]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$24]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$24(ASC)] HASH:[$$24]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$24]  |PARTITIONED|
               -- SORT_GROUP_BY[$$16]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_01.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_01.plan
index 3fbd339..e0a20c8 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_01.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_01.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_02.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_02.plan
index e3baddf..c30de53 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_02.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive-open_02.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_01.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_01.plan
index 3fbd339..e0a20c8 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_01.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_01.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_02.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_02.plan
index e3baddf..c30de53 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_02.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/orders-index-search-conjunctive_02.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/q01_pricing_summary_report_nt.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/q01_pricing_summary_report_nt.plan
index fb35c0c..d0b7ef3 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/q01_pricing_summary_report_nt.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/q01_pricing_summary_report_nt.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC), $$3(ASC)] HASH:[$$2, $$3]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC), $$3(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2, $$3]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/q2.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/q2.plan
index 87aa995..cdcee3a 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/q2.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/q2.plan
@@ -22,21 +22,23 @@
                                         }
                                   -- NESTED_TUPLE_SOURCE  |LOCAL|
                             }
-                      -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$32(ASC), $$33(ASC)] HASH:[$$32]  |PARTITIONED|
-                        -- SORT_GROUP_BY[$$23, $$24]  |PARTITIONED|
-                                {
-                                  -- AGGREGATE  |LOCAL|
-                                    -- NESTED_TUPLE_SOURCE  |LOCAL|
-                                }
-                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                            -- STREAM_PROJECT  |PARTITIONED|
-                              -- ASSIGN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- STABLE_SORT [$$32(ASC), $$33(ASC)]  |PARTITIONED|
+                          -- HASH_PARTITION_EXCHANGE [$$32]  |PARTITIONED|
+                            -- SORT_GROUP_BY[$$23, $$24]  |PARTITIONED|
+                                    {
+                                      -- AGGREGATE  |LOCAL|
+                                        -- NESTED_TUPLE_SOURCE  |LOCAL|
+                                    }
+                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                                 -- STREAM_PROJECT  |PARTITIONED|
-                                  -- UNNEST  |PARTITIONED|
+                                  -- ASSIGN  |PARTITIONED|
                                     -- STREAM_PROJECT  |PARTITIONED|
-                                      -- ASSIGN  |PARTITIONED|
+                                      -- UNNEST  |PARTITIONED|
                                         -- STREAM_PROJECT  |PARTITIONED|
-                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                            -- DATASOURCE_SCAN  |PARTITIONED|
+                                          -- ASSIGN  |PARTITIONED|
+                                            -- STREAM_PROJECT  |PARTITIONED|
                                               -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                -- DATASOURCE_SCAN  |PARTITIONED|
+                                                  -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1263.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1263.plan
index 8532218..ab10f2d 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1263.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1263.plan
@@ -19,17 +19,19 @@
                           -- ASSIGN  |LOCAL|
                             -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$27(ASC), $$28(ASC)] HASH:[$$27]  |PARTITIONED|
-              -- SORT_GROUP_BY[$$18, $$24]  |PARTITIONED|
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                  -- STREAM_PROJECT  |PARTITIONED|
-                    -- ASSIGN  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+              -- STABLE_SORT [$$27(ASC)]  |PARTITIONED|
+                -- HASH_PARTITION_EXCHANGE [$$27]  |PARTITIONED|
+                  -- SORT_GROUP_BY[$$18, $$24]  |PARTITIONED|
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
+                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                       -- STREAM_PROJECT  |PARTITIONED|
-                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                          -- DATASOURCE_SCAN  |PARTITIONED|
+                        -- ASSIGN  |PARTITIONED|
+                          -- STREAM_PROJECT  |PARTITIONED|
                             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                              -- DATASOURCE_SCAN  |PARTITIONED|
+                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                  -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-2.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-2.plan
index 1dac8b2..cb833a5 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-2.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-2.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$3(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$39]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$39]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$39(ASC)] HASH:[$$39]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$39]  |PARTITIONED|
               -- SORT_GROUP_BY[$$27]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
@@ -29,11 +29,13 @@
                                         -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                           -- PRE_SORTED_DISTINCT_BY  |PARTITIONED|
-                            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$31(ASC)] HASH:[$$31]  |PARTITIONED|
-                              -- STREAM_PROJECT  |PARTITIONED|
-                                -- STREAM_SELECT  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- STABLE_SORT [$$31(ASC)]  |PARTITIONED|
+                                -- HASH_PARTITION_EXCHANGE [$$31]  |PARTITIONED|
                                   -- STREAM_PROJECT  |PARTITIONED|
-                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                      -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- STREAM_SELECT  |PARTITIONED|
+                                      -- STREAM_PROJECT  |PARTITIONED|
                                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                          -- DATASOURCE_SCAN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-3.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-3.plan
index b084028..336d7d4 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-3.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-3.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$3(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$39]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$39]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$39(ASC)] HASH:[$$39]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$39]  |PARTITIONED|
               -- SORT_GROUP_BY[$$27]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
@@ -29,11 +29,13 @@
                                         -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                           -- PRE_SORTED_DISTINCT_BY  |PARTITIONED|
-                            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$31(ASC)] HASH:[$$31]  |PARTITIONED|
-                              -- STREAM_PROJECT  |PARTITIONED|
-                                -- STREAM_SELECT  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- STABLE_SORT [$$31(ASC)]  |PARTITIONED|
+                                -- HASH_PARTITION_EXCHANGE [$$31]  |PARTITIONED|
                                   -- STREAM_PROJECT  |PARTITIONED|
-                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                      -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- STREAM_SELECT  |PARTITIONED|
+                                      -- STREAM_PROJECT  |PARTITIONED|
                                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                          -- DATASOURCE_SCAN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-4.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-4.plan
index 4a3162f..5e3d14a 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-4.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343-4.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$3(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$39]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$39]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$39(ASC)] HASH:[$$39]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$39]  |PARTITIONED|
               -- SORT_GROUP_BY[$$27]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
@@ -36,11 +36,13 @@
                                                       -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                           -- PRE_SORTED_DISTINCT_BY  |PARTITIONED|
-                            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$31(ASC)] HASH:[$$31]  |PARTITIONED|
-                              -- STREAM_PROJECT  |PARTITIONED|
-                                -- STREAM_SELECT  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- STABLE_SORT [$$31(ASC)]  |PARTITIONED|
+                                -- HASH_PARTITION_EXCHANGE [$$31]  |PARTITIONED|
                                   -- STREAM_PROJECT  |PARTITIONED|
-                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                      -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- STREAM_SELECT  |PARTITIONED|
+                                      -- STREAM_PROJECT  |PARTITIONED|
                                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                          -- DATASOURCE_SCAN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343.plan
index 1dac8b2..cb833a5 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-1343.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$3(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$39]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$39]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$39(ASC)] HASH:[$$39]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$39]  |PARTITIONED|
               -- SORT_GROUP_BY[$$27]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
@@ -29,11 +29,13 @@
                                         -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                           -- PRE_SORTED_DISTINCT_BY  |PARTITIONED|
-                            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$31(ASC)] HASH:[$$31]  |PARTITIONED|
-                              -- STREAM_PROJECT  |PARTITIONED|
-                                -- STREAM_SELECT  |PARTITIONED|
+                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                              -- STABLE_SORT [$$31(ASC)]  |PARTITIONED|
+                                -- HASH_PARTITION_EXCHANGE [$$31]  |PARTITIONED|
                                   -- STREAM_PROJECT  |PARTITIONED|
-                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                      -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- STREAM_SELECT  |PARTITIONED|
+                                      -- STREAM_PROJECT  |PARTITIONED|
                                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                          -- DATASOURCE_SCAN  |PARTITIONED|
+                                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                              -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-830.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-830.plan
index ef384eb..26185a2 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-830.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-ASTERIXDB-830.plan
@@ -12,39 +12,41 @@
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$32(ASC)] HASH:[$$32]  |PARTITIONED|
-              -- PRE_CLUSTERED_GROUP_BY[$$24]  |PARTITIONED|
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                  -- STABLE_SORT [$$24(ASC)]  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+              -- STABLE_SORT [$$32(ASC)]  |PARTITIONED|
+                -- HASH_PARTITION_EXCHANGE [$$32]  |PARTITIONED|
+                  -- PRE_CLUSTERED_GROUP_BY[$$24]  |PARTITIONED|
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                      -- STREAM_PROJECT  |PARTITIONED|
-                        -- ASSIGN  |PARTITIONED|
-                          -- STREAM_SELECT  |PARTITIONED|
+                      -- STABLE_SORT [$$24(ASC)]  |PARTITIONED|
+                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                          -- STREAM_PROJECT  |PARTITIONED|
                             -- ASSIGN  |PARTITIONED|
-                              -- STREAM_PROJECT  |PARTITIONED|
-                                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                  -- DATASOURCE_SCAN  |PARTITIONED|
+                              -- STREAM_SELECT  |PARTITIONED|
+                                -- ASSIGN  |PARTITIONED|
+                                  -- STREAM_PROJECT  |PARTITIONED|
                                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                      -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                      -- DATASOURCE_SCAN  |PARTITIONED|
+                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$40]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$40]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$40(ASC)] HASH:[$$40]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$40]  |PARTITIONED|
               -- SORT_GROUP_BY[$$30]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue562.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue562.plan
index 931ec7d..173aae7 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue562.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue562.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$7(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$82]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$82]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$82(ASC)] HASH:[$$82]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$82]  |PARTITIONED|
               -- SORT_GROUP_BY[$$11]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
@@ -19,12 +19,12 @@
                     -- STREAM_SELECT  |PARTITIONED|
                       -- STREAM_PROJECT  |PARTITIONED|
                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                          -- PRE_CLUSTERED_GROUP_BY[$$79]  |PARTITIONED|
+                          -- SORT_GROUP_BY[$$79]  |PARTITIONED|
                                   {
                                     -- AGGREGATE  |LOCAL|
                                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                                   }
-                            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$79(ASC)] HASH:[$$79]  |PARTITIONED|
+                            -- HASH_PARTITION_EXCHANGE [$$79]  |PARTITIONED|
                               -- PRE_CLUSTERED_GROUP_BY[$$75]  |PARTITIONED|
                                       {
                                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue601.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue601.plan
index 7b628a7..369f475 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue601.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue601.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$13]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$13]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$13(ASC)] HASH:[$$13]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$13]  |PARTITIONED|
               -- SORT_GROUP_BY[$$10]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue697.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue697.plan
index e2a985d..13fb7e1 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue697.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue697.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$19]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$19]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$19(ASC)] HASH:[$$19]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$19]  |PARTITIONED|
               -- PRE_CLUSTERED_GROUP_BY[$$16]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue785.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue785.plan
index ac2c294..4027e6a 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue785.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue785.plan
@@ -13,12 +13,12 @@
             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
               -- STABLE_SORT [$$7(ASC)]  |PARTITIONED|
                 -- HASH_PARTITION_EXCHANGE [$$7]  |PARTITIONED|
-                  -- PRE_CLUSTERED_GROUP_BY[$$69, $$70]  |PARTITIONED|
+                  -- SORT_GROUP_BY[$$69, $$70]  |PARTITIONED|
                           {
                             -- AGGREGATE  |LOCAL|
                               -- NESTED_TUPLE_SOURCE  |LOCAL|
                           }
-                    -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$69(ASC), $$70(ASC)] HASH:[$$69, $$70]  |PARTITIONED|
+                    -- HASH_PARTITION_EXCHANGE [$$69, $$70]  |PARTITIONED|
                       -- SORT_GROUP_BY[$$50, $$54]  |PARTITIONED|
                               {
                                 -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810-2.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810-2.plan
index 2b98aec..7b94c2a 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810-2.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810-2.plan
@@ -16,29 +16,31 @@
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$75(ASC), $$76(ASC)] HASH:[$$75, $$76]  |PARTITIONED|
-              -- PRE_CLUSTERED_GROUP_BY[$$42, $$43]  |PARTITIONED|
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- STREAM_SELECT  |LOCAL|
-                            -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- STREAM_SELECT  |LOCAL|
-                            -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                  -- STABLE_SORT [$$42(ASC), $$43(ASC)]  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+              -- STABLE_SORT [$$75(ASC), $$76(ASC)]  |PARTITIONED|
+                -- HASH_PARTITION_EXCHANGE [$$75, $$76]  |PARTITIONED|
+                  -- PRE_CLUSTERED_GROUP_BY[$$42, $$43]  |PARTITIONED|
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- STREAM_SELECT  |LOCAL|
+                                -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- STREAM_SELECT  |LOCAL|
+                                -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                      -- STREAM_SELECT  |PARTITIONED|
-                        -- ASSIGN  |PARTITIONED|
-                          -- STREAM_PROJECT  |PARTITIONED|
-                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                              -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- STABLE_SORT [$$42(ASC), $$43(ASC)]  |PARTITIONED|
+                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                          -- STREAM_SELECT  |PARTITIONED|
+                            -- ASSIGN  |PARTITIONED|
+                              -- STREAM_PROJECT  |PARTITIONED|
                                 -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                  -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                  -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                      -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810.plan
index fc4ab7d..3e7d5d9 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/query-issue810.plan
@@ -12,25 +12,27 @@
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$34(ASC), $$35(ASC)] HASH:[$$34, $$35]  |PARTITIONED|
-              -- PRE_CLUSTERED_GROUP_BY[$$23, $$24]  |PARTITIONED|
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- STREAM_SELECT  |LOCAL|
-                            -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                      {
-                        -- AGGREGATE  |LOCAL|
-                          -- STREAM_SELECT  |LOCAL|
-                            -- NESTED_TUPLE_SOURCE  |LOCAL|
-                      }
-                -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                  -- STABLE_SORT [$$23(ASC), $$24(ASC)]  |PARTITIONED|
+            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+              -- STABLE_SORT [$$34(ASC), $$35(ASC)]  |PARTITIONED|
+                -- HASH_PARTITION_EXCHANGE [$$34, $$35]  |PARTITIONED|
+                  -- PRE_CLUSTERED_GROUP_BY[$$23, $$24]  |PARTITIONED|
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- STREAM_SELECT  |LOCAL|
+                                -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
+                          {
+                            -- AGGREGATE  |LOCAL|
+                              -- STREAM_SELECT  |LOCAL|
+                                -- NESTED_TUPLE_SOURCE  |LOCAL|
+                          }
                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                      -- STREAM_SELECT  |PARTITIONED|
-                        -- ASSIGN  |PARTITIONED|
-                          -- STREAM_PROJECT  |PARTITIONED|
-                            -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                              -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- STABLE_SORT [$$23(ASC), $$24(ASC)]  |PARTITIONED|
+                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                          -- STREAM_SELECT  |PARTITIONED|
+                            -- ASSIGN  |PARTITIONED|
+                              -- STREAM_PROJECT  |PARTITIONED|
                                 -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                  -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                  -- DATASOURCE_SCAN  |PARTITIONED|
+                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                      -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index-open.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index-open.plan
index f77dc35..2b07c56 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index-open.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index-open.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index.plan
index f77dc35..2b07c56 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/rtree-secondary-index.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/scan-delete-rtree-secondary-index.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/scan-delete-rtree-secondary-index.plan
index 317b163..2562338 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/scan-delete-rtree-secondary-index.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/scan-delete-rtree-secondary-index.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- COMMIT  |PARTITIONED|
   -- STREAM_PROJECT  |PARTITIONED|
     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
@@ -28,4 +30,4 @@
                                 -- BTREE_SEARCH  |PARTITIONED|
                                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                                     -- ASSIGN  |PARTITIONED|
-                                      -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
\ No newline at end of file
+                                      -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-secondary-index.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-secondary-index.plan
index 1534f6c..49535e9 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-secondary-index.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/skip-index/skip-rtree-secondary-index.plan
@@ -3,12 +3,14 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
         -- BULKLOAD  |PARTITIONED|
-          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$2(ASC)] HASH:[$$2]  |PARTITIONED|
-            -- ASSIGN  |PARTITIONED|
-              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                -- DATASOURCE_SCAN  |PARTITIONED|
+          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+            -- STABLE_SORT [$$2(ASC)]  |PARTITIONED|
+              -- HASH_PARTITION_EXCHANGE [$$2]  |PARTITIONED|
+                -- ASSIGN  |PARTITIONED|
                   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                    -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                    -- DATASOURCE_SCAN  |PARTITIONED|
+                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                        -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
 -- DISTRIBUTE_RESULT  |PARTITIONED|
   -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
     -- STREAM_PROJECT  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/split-materialization-above-join.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/split-materialization-above-join.plan
index 5d9600c..d698437 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/split-materialization-above-join.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/split-materialization-above-join.plan
@@ -69,12 +69,12 @@
                                                                                           -- SORT_MERGE_EXCHANGE [$$102(ASC), $$18(ASC) ]  |PARTITIONED|
                                                                                             -- STABLE_SORT [$$102(ASC), $$18(ASC)]  |PARTITIONED|
                                                                                               -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                                                                -- PRE_CLUSTERED_GROUP_BY[$$130]  |PARTITIONED|
+                                                                                                -- SORT_GROUP_BY[$$130]  |PARTITIONED|
                                                                                                         {
                                                                                                           -- AGGREGATE  |LOCAL|
                                                                                                             -- NESTED_TUPLE_SOURCE  |LOCAL|
                                                                                                         }
-                                                                                                  -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$130(ASC)] HASH:[$$130]  |PARTITIONED|
+                                                                                                  -- HASH_PARTITION_EXCHANGE [$$130]  |PARTITIONED|
                                                                                                     -- SORT_GROUP_BY[$$17]  |PARTITIONED|
                                                                                                             {
                                                                                                               -- AGGREGATE  |LOCAL|
@@ -126,12 +126,12 @@
                                                                                     -- SORT_MERGE_EXCHANGE [$$102(ASC), $$18(ASC) ]  |PARTITIONED|
                                                                                       -- STABLE_SORT [$$102(ASC), $$18(ASC)]  |PARTITIONED|
                                                                                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                                                          -- PRE_CLUSTERED_GROUP_BY[$$130]  |PARTITIONED|
+                                                                                          -- SORT_GROUP_BY[$$130]  |PARTITIONED|
                                                                                                   {
                                                                                                     -- AGGREGATE  |LOCAL|
                                                                                                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                                                                                                   }
-                                                                                            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$130(ASC)] HASH:[$$130]  |PARTITIONED|
+                                                                                            -- HASH_PARTITION_EXCHANGE [$$130]  |PARTITIONED|
                                                                                               -- SORT_GROUP_BY[$$17]  |PARTITIONED|
                                                                                                       {
                                                                                                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/exists.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/exists.plan
index a379cb8..3724559 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/exists.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/exists.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$31(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$104]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$104]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$104(ASC)] HASH:[$$104]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$104]  |PARTITIONED|
               -- SORT_GROUP_BY[$$81]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
@@ -21,12 +21,12 @@
                         -- STREAM_SELECT  |PARTITIONED|
                           -- STREAM_PROJECT  |PARTITIONED|
                             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                              -- PRE_CLUSTERED_GROUP_BY[$$101]  |PARTITIONED|
+                              -- SORT_GROUP_BY[$$101]  |PARTITIONED|
                                       {
                                         -- AGGREGATE  |LOCAL|
                                           -- NESTED_TUPLE_SOURCE  |LOCAL|
                                       }
-                                -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$101(ASC)] HASH:[$$101]  |PARTITIONED|
+                                -- HASH_PARTITION_EXCHANGE [$$101]  |PARTITIONED|
                                   -- PRE_CLUSTERED_GROUP_BY[$$95]  |PARTITIONED|
                                           {
                                             -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/not_exists.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/not_exists.plan
index bc68200..139b084 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/not_exists.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/subquery/not_exists.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$31(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$105]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$105]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$105(ASC)] HASH:[$$105]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$105]  |PARTITIONED|
               -- SORT_GROUP_BY[$$82]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
@@ -21,12 +21,12 @@
                         -- STREAM_SELECT  |PARTITIONED|
                           -- STREAM_PROJECT  |PARTITIONED|
                             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                              -- PRE_CLUSTERED_GROUP_BY[$$102]  |PARTITIONED|
+                              -- SORT_GROUP_BY[$$102]  |PARTITIONED|
                                       {
                                         -- AGGREGATE  |LOCAL|
                                           -- NESTED_TUPLE_SOURCE  |LOCAL|
                                       }
-                                -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$102(ASC)] HASH:[$$102]  |PARTITIONED|
+                                -- HASH_PARTITION_EXCHANGE [$$102]  |PARTITIONED|
                                   -- PRE_CLUSTERED_GROUP_BY[$$96]  |PARTITIONED|
                                           {
                                             -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1580.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1580.plan
index 5e73419..80bb3f4 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1580.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1580.plan
@@ -12,12 +12,12 @@
                       -- STREAM_PROJECT  |PARTITIONED|
                         -- STREAM_SELECT  |PARTITIONED|
                           -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                            -- PRE_CLUSTERED_GROUP_BY[$$95]  |PARTITIONED|
+                            -- SORT_GROUP_BY[$$95]  |PARTITIONED|
                                     {
                                       -- AGGREGATE  |LOCAL|
                                         -- NESTED_TUPLE_SOURCE  |LOCAL|
                                     }
-                              -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$95(ASC)] HASH:[$$95]  |PARTITIONED|
+                              -- HASH_PARTITION_EXCHANGE [$$95]  |PARTITIONED|
                                 -- SORT_GROUP_BY[$$73]  |PARTITIONED|
                                         {
                                           -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1591.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1591.plan
index 03ad253..2ade8bb 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1591.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpcds/query-ASTERIXDB-1591.plan
@@ -10,12 +10,12 @@
                   -- STREAM_SELECT  |PARTITIONED|
                     -- STREAM_PROJECT  |PARTITIONED|
                       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                        -- PRE_CLUSTERED_GROUP_BY[$$129, $$130]  |PARTITIONED|
+                        -- SORT_GROUP_BY[$$129, $$130]  |PARTITIONED|
                                 {
                                   -- AGGREGATE  |LOCAL|
                                     -- NESTED_TUPLE_SOURCE  |LOCAL|
                                 }
-                          -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$129(ASC), $$130(ASC)] HASH:[$$129, $$130]  |PARTITIONED|
+                          -- HASH_PARTITION_EXCHANGE [$$129, $$130]  |PARTITIONED|
                             -- PRE_CLUSTERED_GROUP_BY[$$117, $$118]  |PARTITIONED|
                                     {
                                       -- AGGREGATE  |LOCAL|
@@ -29,12 +29,12 @@
                                       -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                                         -- HYBRID_HASH_JOIN [$$117][$$99]  |PARTITIONED|
                                           -- HASH_PARTITION_EXCHANGE [$$117]  |PARTITIONED|
-                                            -- PRE_CLUSTERED_GROUP_BY[$$126, $$127]  |PARTITIONED|
+                                            -- SORT_GROUP_BY[$$126, $$127]  |PARTITIONED|
                                                     {
                                                       -- AGGREGATE  |LOCAL|
                                                         -- NESTED_TUPLE_SOURCE  |LOCAL|
                                                     }
-                                              -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$126(ASC), $$127(ASC)] HASH:[$$126, $$127]  |PARTITIONED|
+                                              -- HASH_PARTITION_EXCHANGE [$$126, $$127]  |PARTITIONED|
                                                 -- PRE_CLUSTERED_GROUP_BY[$$114, $$115]  |PARTITIONED|
                                                         {
                                                           -- AGGREGATE  |LOCAL|
@@ -51,12 +51,12 @@
                                                                 -- STREAM_PROJECT  |PARTITIONED|
                                                                   -- STREAM_SELECT  |PARTITIONED|
                                                                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                                      -- PRE_CLUSTERED_GROUP_BY[$$123, $$124]  |PARTITIONED|
+                                                                      -- SORT_GROUP_BY[$$123, $$124]  |PARTITIONED|
                                                                               {
                                                                                 -- AGGREGATE  |LOCAL|
                                                                                   -- NESTED_TUPLE_SOURCE  |LOCAL|
                                                                               }
-                                                                        -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$123(ASC), $$124(ASC)] HASH:[$$123, $$124]  |PARTITIONED|
+                                                                        -- HASH_PARTITION_EXCHANGE [$$123, $$124]  |PARTITIONED|
                                                                           -- PRE_CLUSTERED_GROUP_BY[$$78, $$79]  |PARTITIONED|
                                                                                   {
                                                                                     -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping.plan
index 754e03b..ad011cb 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$12(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$104]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$104]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$104(ASC)] HASH:[$$104]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$104]  |PARTITIONED|
               -- SORT_GROUP_BY[$$86]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping_broadcast.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping_broadcast.plan
index 773b4db..27108be 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping_broadcast.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/tpch/q12_shipping_broadcast.plan
@@ -3,12 +3,12 @@
     -- STREAM_PROJECT  |PARTITIONED|
       -- ASSIGN  |PARTITIONED|
         -- SORT_MERGE_EXCHANGE [$$12(ASC) ]  |PARTITIONED|
-          -- PRE_CLUSTERED_GROUP_BY[$$104]  |PARTITIONED|
+          -- SORT_GROUP_BY[$$104]  |PARTITIONED|
                   {
                     -- AGGREGATE  |LOCAL|
                       -- NESTED_TUPLE_SOURCE  |LOCAL|
                   }
-            -- HASH_PARTITION_MERGE_EXCHANGE MERGE:[$$104(ASC)] HASH:[$$104]  |PARTITIONED|
+            -- HASH_PARTITION_EXCHANGE [$$104]  |PARTITIONED|
               -- SORT_GROUP_BY[$$86]  |PARTITIONED|
                       {
                         -- AGGREGATE  |LOCAL|
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_20M/big_object_load_20M.2.update.aql b/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_20M/big_object_load_20M.2.update.aql
index d8895f6..f384e96 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_20M/big_object_load_20M.2.update.aql
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_20M/big_object_load_20M.2.update.aql
@@ -25,6 +25,9 @@
 
 use dataverse testdv2;
 
+
+set hash_merge "true"
+
 load dataset testds
 using localfs
 (("path"="asterix_nc1://target/data/big-object/big_object_20M.adm"),("format"="adm")) pre-sorted;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_only_20M/big_object_load_only_20M.2.update.aql b/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_only_20M/big_object_load_only_20M.2.update.aql
index d8895f6..f384e96 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_only_20M/big_object_load_only_20M.2.update.aql
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries/big-object/big_object_load_only_20M/big_object_load_only_20M.2.update.aql
@@ -25,6 +25,9 @@
 
 use dataverse testdv2;
 
+
+set hash_merge "true"
+
 load dataset testds
 using localfs
 (("path"="asterix_nc1://target/data/big-object/big_object_20M.adm"),("format"="adm")) pre-sorted;
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.query.sqlpp b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.query.sqlpp
index b6dd0c0..9ac57fd 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.query.sqlpp
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/queries_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.query.sqlpp
@@ -19,8 +19,7 @@
 
 use tpch;
 
-
-set `import-private-functions` `true`;
+set hash_merge "true"
 
 select element {'l_returnflag':l_returnflag,'l_linestatus':l_linestatus,'sum_qty':COLL_SUM((
         select element i.l_quantity
diff --git a/asterixdb/asterix-app/src/test/resources/runtimets/results_parser_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.ast b/asterixdb/asterix-app/src/test/resources/runtimets/results_parser_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.ast
index 815615d..54fe3f5 100644
--- a/asterixdb/asterix-app/src/test/resources/runtimets/results_parser_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.ast
+++ b/asterixdb/asterix-app/src/test/resources/runtimets/results_parser_sqlpp/tpch/q01_pricing_summary_report_nt/q01_pricing_summary_report_nt.3.ast
@@ -1,5 +1,5 @@
 DataverseUse tpch
-Set import-private-functions=true
+Set hash_merge=true
 Query:
 SELECT ELEMENT [
 RecordConstructor [
diff --git a/asterixdb/asterix-installer/src/test/resources/transactionts/queries/query_after_restart/big_object_20M/big_object_20M.3.update.aql b/asterixdb/asterix-installer/src/test/resources/transactionts/queries/query_after_restart/big_object_20M/big_object_20M.3.update.aql
index f1b3819..b99ccdc 100644
--- a/asterixdb/asterix-installer/src/test/resources/transactionts/queries/query_after_restart/big_object_20M/big_object_20M.3.update.aql
+++ b/asterixdb/asterix-installer/src/test/resources/transactionts/queries/query_after_restart/big_object_20M/big_object_20M.3.update.aql
@@ -25,6 +25,8 @@
 
 use dataverse testdv2;
 
+set hash_merge "true"
+
 load dataset testds
 using localfs
 (("path"="asterix_nc1://../../../../../../asterix-app/target/data/big-object/big_object_20M.adm"),("format"="adm")) pre-sorted;
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/metadata/IMetadataProvider.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/metadata/IMetadataProvider.java
index 6947942..5d1f402 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/metadata/IMetadataProvider.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/metadata/IMetadataProvider.java
@@ -19,6 +19,7 @@
 package org.apache.hyracks.algebricks.core.algebra.metadata;
 
 import java.util.List;
+import java.util.Map;
 
 import org.apache.hyracks.algebricks.common.constraints.AlgebricksPartitionConstraint;
 import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
@@ -205,4 +206,5 @@
             List<LogicalVariable> prevSecondaryKeys, LogicalVariable prevAdditionalFilteringKeys,
             RecordDescriptor inputDesc, JobGenContext context, JobSpecification spec) throws AlgebricksException;
 
+    public Map<String, String> getConfig();
 }
diff --git a/hyracks-fullstack/algebricks/algebricks-examples/piglet-example/src/main/java/org/apache/hyracks/algebricks/examples/piglet/metadata/PigletMetadataProvider.java b/hyracks-fullstack/algebricks/algebricks-examples/piglet-example/src/main/java/org/apache/hyracks/algebricks/examples/piglet/metadata/PigletMetadataProvider.java
index 35b433b..3f7f56d 100644
--- a/hyracks-fullstack/algebricks/algebricks-examples/piglet-example/src/main/java/org/apache/hyracks/algebricks/examples/piglet/metadata/PigletMetadataProvider.java
+++ b/hyracks-fullstack/algebricks/algebricks-examples/piglet-example/src/main/java/org/apache/hyracks/algebricks/examples/piglet/metadata/PigletMetadataProvider.java
@@ -253,4 +253,9 @@
         // TODO Auto-generated method stub
         return null;
     }
+
+    @Override
+    public Map<String, String> getConfig() {
+        return Collections.emptyMap();
+    }
 }
diff --git a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/EnforceStructuralPropertiesRule.java b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/EnforceStructuralPropertiesRule.java
index 159bcf5..0b3a57e 100644
--- a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/EnforceStructuralPropertiesRule.java
+++ b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/EnforceStructuralPropertiesRule.java
@@ -93,6 +93,8 @@
 
 public class EnforceStructuralPropertiesRule implements IAlgebraicRewriteRule {
 
+    private static final String HASH_MERGE = "hash_merge";
+    private static final String TRUE_CONSTANT = "true";
     private PhysicalOptimizationConfig physicalOptimizationConfig;
 
     @Override
@@ -552,6 +554,11 @@
                 }
                 case UNORDERED_PARTITIONED: {
                     List<LogicalVariable> varList = new ArrayList<>(((UnorderedPartitionedProperty) pp).getColumnSet());
+                    String hashMergeHint = context.getMetadataProvider().getConfig().get(HASH_MERGE);
+                    if (hashMergeHint == null || !hashMergeHint.equalsIgnoreCase(TRUE_CONSTANT)) {
+                        pop = new HashPartitionExchangePOperator(varList, domain);
+                        break;
+                    }
                     List<ILocalStructuralProperty> cldLocals = deliveredByChild.getLocalProperties();
                     List<ILocalStructuralProperty> reqdLocals = required.getLocalProperties();
                     boolean propWasSet = false;