Add additional Method that check whether a table is empty or not

Application Devleopers are using queryNumEntries API
implemented by "COUNT(*)" to check whether a table is empty or not.
COUNT(*)  has to process the entire table to compute the result.
But, "EXISTS" can stop after a single matching row has been found.
So, Using "EXISTS" is more faster than "COUNT(*)"
I added new API using "EXISTS" to check whether a table is empty or not

Change-Id: Idcc2633d0a5349c59f41e125cf34c9dc6622cdbe

core/java/android/database/DatabaseUtils.java

@@ -791,6 +791,18 @@ public class DatabaseUtils {
                     selectionArgs);
     }
 
+    /**
+     * Query the table to check whether a table is empty or not
+     * @param db the database the table is in
+     * @param table the name of the table to query
+     * @return True if the table is empty
+     * @hide
+     */
+    public static boolean queryIsEmpty(SQLiteDatabase db, String table) {
+        long isEmpty = longForQuery(db, "select exists(select 1 from " + table + ")", null);
+        return isEmpty == 0;
+    }
+
     /**
      * Utility method to run the query on the db and return the value in the
      * first column of the first row.