diff --git a/core/workflow-operator/src/main/scala/edu/uci/ics/amber/operator/SpecialPhysicalOpFactory.scala b/core/workflow-operator/src/main/scala/edu/uci/ics/amber/operator/SpecialPhysicalOpFactory.scala
index 541c1c9712..6b63010894 100644
--- a/core/workflow-operator/src/main/scala/edu/uci/ics/amber/operator/SpecialPhysicalOpFactory.scala
+++ b/core/workflow-operator/src/main/scala/edu/uci/ics/amber/operator/SpecialPhysicalOpFactory.scala
@@ -7,7 +7,7 @@ import edu.uci.ics.amber.operator.sink.ProgressiveUtils
 import edu.uci.ics.amber.operator.sink.managed.ProgressiveSinkOpExec
 import edu.uci.ics.amber.virtualidentity.{ExecutionIdentity, OperatorIdentity, WorkflowIdentity}
 import edu.uci.ics.amber.workflow.OutputPort.OutputMode
-import edu.uci.ics.amber.workflow.OutputPort.OutputMode.SET_SNAPSHOT
+import edu.uci.ics.amber.workflow.OutputPort.OutputMode.{SET_DELTA, SET_SNAPSHOT, SINGLE_SNAPSHOT}
 import edu.uci.ics.amber.workflow.{InputPort, OutputPort, PortIdentity}
 
 object SpecialPhysicalOpFactory {
@@ -38,21 +38,23 @@ object SpecialPhysicalOpFactory {
           val inputSchema = inputSchemas.values.head
 
           // Define outputSchema based on outputMode
-          val outputSchema = if (outputMode == SET_SNAPSHOT) {
-            if (inputSchema.containsAttribute(ProgressiveUtils.insertRetractFlagAttr.getName)) {
-              // input is insert/retract delta: remove the flag column in the output
-              Schema
-                .builder()
-                .add(inputSchema)
-                .remove(ProgressiveUtils.insertRetractFlagAttr.getName)
-                .build()
-            } else {
-              // input is insert-only delta: output schema is the same as input schema
+          val outputSchema = outputMode match {
+            case SET_SNAPSHOT | SINGLE_SNAPSHOT =>
+              if (inputSchema.containsAttribute(ProgressiveUtils.insertRetractFlagAttr.getName)) {
+                // with insert/retract delta: remove the flag column
+                Schema
+                  .builder()
+                  .add(inputSchema)
+                  .remove(ProgressiveUtils.insertRetractFlagAttr.getName)
+                  .build()
+              } else {
+                // with insert-only delta: output schema is the same as input schema
+                inputSchema
+              }
+
+            case SET_DELTA =>
+              // output schema is the same as input schema
               inputSchema
-            }
-          } else {
-            // SET_DELTA: output schema is the same as input schema
-            inputSchema
           }
 
           // Create a Scala immutable Map