[NO ISSUE] use isExternal() in lieu of instanceof

- user model changes: no
- storage format changes: no
- interface changes: yes

Details:

Add a default method for determining whether an IFunctionInfo
represents an external function or not, which is overriden by
ExternalFunctionInfo. This is much cleaner than abusing
instanceof to determine this.

Change-Id: I50539b9a8a3419a389590ea89230c7e5642c277b
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/asterixdb/+/15543
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Contrib: Ian Maxon <imaxon@uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Ian Maxon <imaxon@uci.edu>
Reviewed-by: Hussain Towaileb <hussainht@gmail.com>

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 @@ private IScalarEvaluatorFactory createScalarFunctionEvaluatorFactory(AbstractFun
             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 {

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 int countConstantArgs(List<Mutable<ILogicalExpression>> argList) {
         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

asterixdb/asterix-metadata/src/main/java/org/apache/asterix/metadata/functions/ExternalFunctionCompilerUtil.java

@@ -174,7 +174,7 @@ public static boolean supportsBatchInvocation(FunctionKind fnKind, IFunctionInfo
         if (fnKind != FunctionKind.SCALAR) {
             return false;
         }
-        if (!(fnInfo instanceof IExternalFunctionInfo)) {
+        if (!fnInfo.isExternal()) {
             return false;
         }
         ExternalFunctionLanguage language = ((IExternalFunctionInfo) fnInfo).getLanguage();

asterixdb/asterix-om/src/main/java/org/apache/asterix/om/functions/ExternalFunctionInfo.java

@@ -101,4 +101,9 @@ public Map<String, String> getResources() {
     public boolean getNullCall() {
         return nullCall;
     }
+
+    @Override
+    public boolean isExternal() {
+        return true;
+    }
 }

hyracks-fullstack/algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/functions/IFunctionInfo.java

@@ -38,6 +38,11 @@ default boolean isFunctional() {
         return true;
     }
 
+    default boolean isExternal() {
+        // A function is not external by default.
+        return false;
+    }
+
     /**
      * @param args,
      *            the arguments.