diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/physical/SinkWritePOperator.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/physical/SinkWritePOperator.java
index 9c1879f..b8c1f36 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/physical/SinkWritePOperator.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/operators/physical/SinkWritePOperator.java
@@ -147,15 +147,24 @@
                 JobGenHelper.variablesToAscBinaryComparatorFactories(partitionVariables, typeEnv, context);
 
         // Key expressions
+        boolean allConstants = true;
         IScalarEvaluatorFactory[] keyEvalFactories = new IScalarEvaluatorFactory[write.getKeyExpressions().size()];
         List<Mutable<ILogicalExpression>> keyExpressions = write.getKeyExpressions();
         if (!keyExpressions.isEmpty()) {
             for (int i = 0; i < keyExpressions.size(); i++) {
                 ILogicalExpression keyExpr = keyExpressions.get(i).getValue();
+                if (keyExpr.getExpressionTag() != LogicalExpressionTag.CONSTANT) {
+                    allConstants = false;
+                }
                 keyEvalFactories[i] = runtimeProvider.createEvaluatorFactory(keyExpr, typeEnv, inputSchemas, context);
             }
         }
 
+        // key cannot be fully constant
+        if (!keyExpressions.isEmpty() && allConstants) {
+            throw AlgebricksException.create(ErrorCode.EXPRESSION_CANNOT_BE_CONSTANT, op.getSourceLocation(), "KEY");
+        }
+
         RecordDescriptor recDesc =
                 JobGenHelper.mkRecordDescriptor(context.getTypeEnvironment(op), propagatedSchema, context);
         RecordDescriptor inputDesc = JobGenHelper.mkRecordDescriptor(
diff --git a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SetAlgebricksPhysicalOperatorsRule.java b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SetAlgebricksPhysicalOperatorsRule.java
index 9fd4cd9..f945994 100644
--- a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SetAlgebricksPhysicalOperatorsRule.java
+++ b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SetAlgebricksPhysicalOperatorsRule.java
@@ -408,7 +408,6 @@
             }
             ensureAllVariables(op.getPartitionExpressions(), v -> v);
             ensureAllVariables(op.getOrderExpressions(), Pair::getSecond);
-            ensureAllVariables(op.getKeyExpressions(), v -> v);
             return new SinkWritePOperator(op.getSourceVariable(), op.getPartitionVariables(), op.getOrderColumns());
         }
 
diff --git a/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/exceptions/ErrorCode.java b/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/exceptions/ErrorCode.java
index 177117e..e46c0ef 100644
--- a/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/exceptions/ErrorCode.java
+++ b/hyracks-fullstack/hyracks/hyracks-api/src/main/java/org/apache/hyracks/api/exceptions/ErrorCode.java
@@ -166,7 +166,8 @@
     OPERATOR_NOT_IMPLEMENTED(10005),
     INAPPLICABLE_HINT(10006),
     CROSS_PRODUCT_JOIN(10007),
-    GROUP_ALL_DECOR(10008);
+    GROUP_ALL_DECOR(10008),
+    EXPRESSION_CANNOT_BE_CONSTANT(10009);
 
     private static final String RESOURCE_PATH = "errormsg/en.properties";
     public static final String HYRACKS = "HYR";
diff --git a/hyracks-fullstack/hyracks/hyracks-api/src/main/resources/errormsg/en.properties b/hyracks-fullstack/hyracks/hyracks-api/src/main/resources/errormsg/en.properties
index ea1cc1e..b3c2d7b 100644
--- a/hyracks-fullstack/hyracks/hyracks-api/src/main/resources/errormsg/en.properties
+++ b/hyracks-fullstack/hyracks/hyracks-api/src/main/resources/errormsg/en.properties
@@ -155,4 +155,5 @@
 10005 = Operator is not implemented: %1$s
 10006 = Could not apply %1$s hint: %2$s
 10007 = Encountered a cross product join
-10008 = Inappropriate use of group by all with decor variables
\ No newline at end of file
+10008 = Inappropriate use of group by all with decor variables
+10009 = '%1$s' expression cannot be a constant
\ No newline at end of file