Marks the IonInputFormat as not splittable, meaning that Ion files wi…

…ll not be split into arbitrarily-sized chunks.

Without additional logic (which is possible to write, but is currently not written) to ensure each chunk contains
a self-contained symbol table context, splitting Ion files will cause errors on read.

serde/src/main/java/com/amazon/ionhiveserde/formats/IonInputFormat.java

@@ -45,6 +45,11 @@ public class IonInputFormat extends FileInputFormat {
 
     private static final Log LOG = LogFactory.getLog(IonInputFormat.class);
 
+    @Override
+    protected boolean isSplitable(final FileSystem fs, final Path filename) {
+        return false;
+    }
+
     @Override
     public RecordReader getRecordReader(final InputSplit split, final JobConf job, final Reporter reporter)
         throws IOException {