diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/jobgen/QueryLogicalExpressionJobGen.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/jobgen/QueryLogicalExpressionJobGen.java
index b1d0b47..b8685d5 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/jobgen/QueryLogicalExpressionJobGen.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/jobgen/QueryLogicalExpressionJobGen.java
@@ -26,7 +26,6 @@
 import org.apache.asterix.external.library.ExternalFunctionDescriptorProvider;
 import org.apache.asterix.metadata.declared.MetadataProvider;
 import org.apache.asterix.om.functions.BuiltinFunctions;
-import org.apache.asterix.om.functions.IExternalFunctionInfo;
 import org.apache.asterix.om.functions.IFunctionDescriptor;
 import org.apache.asterix.om.functions.IFunctionManager;
 import org.apache.asterix.om.functions.IFunctionTypeInferer;
@@ -138,7 +137,7 @@
             throws AlgebricksException {
         IScalarEvaluatorFactory[] args = codegenArguments(expr, env, inputSchemas, context);
         IFunctionDescriptor fd;
-        if (expr.getFunctionInfo() instanceof IExternalFunctionInfo) {
+        if (expr.getFunctionInfo().isExternal()) {
             // Expr is an external function
             fd = ExternalFunctionDescriptorProvider.resolveExternalFunction(expr, env, context);
         } else {
diff --git a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java
index 03d112d..4e496e4 100644
--- a/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java
+++ b/asterixdb/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/ConstantFoldingRule.java
@@ -48,7 +48,6 @@
 import org.apache.asterix.om.base.IAObject;
 import org.apache.asterix.om.constants.AsterixConstantValue;
 import org.apache.asterix.om.functions.BuiltinFunctions;
-import org.apache.asterix.om.functions.IExternalFunctionInfo;
 import org.apache.asterix.om.typecomputer.impl.TypeComputeUtils;
 import org.apache.asterix.om.types.ARecordType;
 import org.apache.asterix.om.types.ATypeTag;
@@ -389,7 +388,7 @@
         private boolean canConstantFold(ScalarFunctionCallExpression function) throws AlgebricksException {
             // skip external functions because they're not available at compile time (on CC)
             IFunctionInfo fi = function.getFunctionInfo();
-            if (fi instanceof IExternalFunctionInfo) {
+            if (fi.isExternal()) {
                 return false;
             }
             // skip all functions that would produce records/arrays/multisets (derived types) in their open format
diff --git a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java
index 5fd96a6..ce98008 100644
--- a/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java
+++ b/asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java
@@ -174,7 +174,7 @@
         if (fnKind != FunctionKind.SCALAR) {
             return false;
         }
-        if (!(fnInfo instanceof IExternalFunctionInfo)) {
+        if (!fnInfo.isExternal()) {
             return false;
         }
         ExternalFunctionLanguage language = ((IExternalFunctionInfo) fnInfo).getLanguage();
diff --git a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
index a3ec9c6..8a2cefa 100644
--- a/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
+++ b/asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java
@@ -101,4 +101,9 @@
     public boolean getNullCall() {
         return nullCall;
     }
+
+    @Override
+    public boolean isExternal() {
+        return true;
+    }
 }
diff --git a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java
index 6e1ccef..34ed225 100644
--- a/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java
+++ b/hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java
@@ -38,6 +38,11 @@
         return true;
     }
 
+    default boolean isExternal() {
+        // A function is not external by default.
+        return false;
+    }
+
     /**
      * @param args,
      *            the arguments.