Common empty resultset query on MySQL returns a row in Vitess

[aquarapid]

A common way to run a query against MySQL that will return an empty resultset is:

select 1 from dual where false;

So, against MySQL:

mysql> select 1 from dual where false;
Empty set (0.00 sec)

But against Vitess:

mysql> select 1 from dual where false;
+-------+
| :vtg1 |
+-------+
|     1 |
+-------+
1 row in set (0.00 sec)

This is not significant per-se, but this query is often used as a connpool "keepalive" query, or as a test query that is expected to return an empty resultset.

[harshit-gangal]

Closed via #6666