diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/AbstractOperatorFromSubplanRewrite.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/AbstractOperatorFromSubplanRewrite.java
index 530596d..acd557e 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/AbstractOperatorFromSubplanRewrite.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/AbstractOperatorFromSubplanRewrite.java
@@ -307,7 +307,7 @@
                 break;
         }
 
-        return combinedCondition;
+        return combinedCondition.cloneExpression();
     }
 
     private SelectOperator getSelectFromPlan(AggregateOperator subplanRoot) {
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/JoinFromSubplanRewrite.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/JoinFromSubplanRewrite.java
index f4fa0fc..7f003a5 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/JoinFromSubplanRewrite.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/array/JoinFromSubplanRewrite.java
@@ -255,9 +255,9 @@
             LogicalVariable newVar = context.newVar();
             VariableReferenceExpression newVarRef = new VariableReferenceExpression(newVar);
             newVarRef.setSourceLocation(joinOp.getSourceLocation());
-            AssignOperator newAssign =
-                    new AssignOperator(newVar, new MutableObject<>(arg.getValue().cloneExpression()));
-            newAssign.setSourceLocation(arg.getValue().getSourceLocation());
+            Mutable<ILogicalExpression> clonedArgRef = new MutableObject<>(arg.getValue().cloneExpression());
+            AssignOperator newAssign = new AssignOperator(newVar, clonedArgRef);
+            newAssign.setSourceLocation(clonedArgRef.getValue().getSourceLocation());
             newAssign.setExecutionMode(joinOp.getExecutionMode());
 
             // Place the new ASSIGN in the appropriate join branch.
diff --git a/asterixdb/asterix-app/src/main/java/org/apache/asterix/utils/RebalanceUtil.java b/asterixdb/asterix-app/src/main/java/org/apache/asterix/utils/RebalanceUtil.java
index b0dc162..ba6c602 100644
--- a/asterixdb/asterix-app/src/main/java/org/apache/asterix/utils/RebalanceUtil.java
+++ b/asterixdb/asterix-app/src/main/java/org/apache/asterix/utils/RebalanceUtil.java
@@ -28,6 +28,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
 import org.apache.asterix.active.IActiveEntityEventsListener;
@@ -371,10 +372,19 @@
     // Creates and loads all secondary indexes for the rebalance target dataset.
     private static void createAndLoadSecondaryIndexesForTarget(Dataset source, Dataset target,
             MetadataProvider metadataProvider, IHyracksClientConnection hcc) throws Exception {
-        for (Index index : metadataProvider.getDatasetIndexes(source.getDataverseName(), source.getDatasetName())) {
-            if (!index.isSecondaryIndex()) {
-                continue;
-            }
+        List<Index> indexes = metadataProvider.getDatasetIndexes(source.getDataverseName(), source.getDatasetName());
+        List<Index> secondaryIndexes = indexes.stream().filter(Index::isSecondaryIndex).collect(Collectors.toList());
+        List<Index> nonSampleIndexes =
+                secondaryIndexes.stream().filter(idx -> !idx.isSampleIndex()).collect(Collectors.toList());
+        List<Index> sampleIndexes = secondaryIndexes.stream().filter(Index::isSampleIndex).collect(Collectors.toList());
+        // must create all non samples secondary indexes first since samples need the stats of secondary indexes
+        createAndLoadIndexes(target, metadataProvider, hcc, nonSampleIndexes);
+        createAndLoadIndexes(target, metadataProvider, hcc, sampleIndexes);
+    }
+
+    private static void createAndLoadIndexes(Dataset target, MetadataProvider metadataProvider,
+            IHyracksClientConnection hcc, List<Index> indexes) throws Exception {
+        for (Index index : indexes) {
             // Creates the secondary index.
             JobSpecification indexCreationJobSpec =
                     IndexUtil.buildSecondaryIndexCreationJobSpec(target, index, metadataProvider, null);
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query8.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query8.plan
index 4d5a668..3f740b0 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query8.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query8.plan
@@ -22,7 +22,7 @@
                             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                               -- PRE_SORTED_DISTINCT_BY  |PARTITIONED|
                                 -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                  -- STABLE_SORT [$$74(ASC), $$75(ASC)]  |PARTITIONED|
+                                  -- STABLE_SORT [$$77(ASC), $$78(ASC)]  |PARTITIONED|
                                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                                       -- STREAM_PROJECT  |PARTITIONED|
                                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
@@ -30,8 +30,9 @@
                                             -- BROADCAST_EXCHANGE  |PARTITIONED|
                                               -- RUNNING_AGGREGATE  |PARTITIONED|
                                                 -- ASSIGN  |PARTITIONED|
-                                                  -- STREAM_PROJECT  |PARTITIONED|
-                                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                      -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
-                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                  -- ASSIGN  |PARTITIONED|
+                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                        -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
+                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query9.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query9.plan
index 5e62aa2..ed318b1 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query9.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query9.plan
@@ -31,7 +31,7 @@
                             -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                               -- PRE_SORTED_DISTINCT_BY  |PARTITIONED|
                                 -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                  -- STABLE_SORT [$$104(ASC), $$105(ASC)]  |PARTITIONED|
+                                  -- STABLE_SORT [$$108(ASC), $$109(ASC)]  |PARTITIONED|
                                     -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
                                       -- STREAM_PROJECT  |PARTITIONED|
                                         -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
@@ -39,8 +39,9 @@
                                             -- BROADCAST_EXCHANGE  |PARTITIONED|
                                               -- RUNNING_AGGREGATE  |PARTITIONED|
                                                 -- ASSIGN  |PARTITIONED|
-                                                  -- STREAM_PROJECT  |PARTITIONED|
-                                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                      -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
-                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                  -- ASSIGN  |PARTITIONED|
+                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                        -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
+                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query8.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query8.plan
index 4d5a668..ea7ceef 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query8.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query8.plan
@@ -30,8 +30,9 @@
                                             -- BROADCAST_EXCHANGE  |PARTITIONED|
                                               -- RUNNING_AGGREGATE  |PARTITIONED|
                                                 -- ASSIGN  |PARTITIONED|
-                                                  -- STREAM_PROJECT  |PARTITIONED|
-                                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                      -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
-                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                  -- ASSIGN  |PARTITIONED|
+                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                        -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
+                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query9.plan b/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query9.plan
index 5e62aa2..b47e122 100644
--- a/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query9.plan
+++ b/asterixdb/asterix-app/src/test/resources/optimizerts/results_cbo/array-index/atomic-and-array-queries/query9.plan
@@ -39,8 +39,9 @@
                                             -- BROADCAST_EXCHANGE  |PARTITIONED|
                                               -- RUNNING_AGGREGATE  |PARTITIONED|
                                                 -- ASSIGN  |PARTITIONED|
-                                                  -- STREAM_PROJECT  |PARTITIONED|
-                                                    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                      -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
-                                                        -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
-                                                          -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
+                                                  -- ASSIGN  |PARTITIONED|
+                                                    -- STREAM_PROJECT  |PARTITIONED|
+                                                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                        -- DATASOURCE_SCAN (TestDataverse.Dataset2)  |PARTITIONED|
+                                                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
+                                                            -- EMPTY_TUPLE_SOURCE  |PARTITIONED|
diff --git a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java
index bbccd65..6b12bf8 100644
--- a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java
+++ b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/entities/Index.java
@@ -138,6 +138,10 @@
         this.pendingOp = pendingOp;
     }
 
+    public boolean isSampleIndex() {
+        return indexType == IndexType.SAMPLE;
+    }
+
     public boolean isSecondaryIndex() {
         return !isPrimaryIndex();
     }