82a4eb
@@ -22,6 +22,7 @@
 import java.lang.reflect.Method;
 import java.net.URL;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
@@ -241,7 +242,7 @@
   /**
    * The mapping from expression function names to expression classes.
    */
-  static Map<String, FunctionInfo> mFunctions = new LinkedHashMap<String, FunctionInfo>();
+  static Map<String, FunctionInfo> mFunctions = Collections.synchronizedMap(new LinkedHashMap<String, FunctionInfo>());
   static {
     registerUDF("concat", UDFConcat.class, false);
     registerUDF("substr", UDFSubstr.class, false);
