Will a query be slowed down if I add a WHERE clause for data?

Transact-SQL
1

I would like to be able to identify the source of the query from within MSSQL using sp_whoisactive. Originally I tried adding a comment to the code before the query. For whatever reason sp_whoisactive sees that once & then removes the comment.

/* Some message here */
SELECT *
FROM [MYDB].[dbo].[FUNCTION]( DEFAULT, DEFAULT )

If I embed the comment as a WHERE clause, mssql won't remove it. Also if I make it some arbitrary text that does not match some other arbitrary text with no reference to a table or column, I imagine there won't be any performance issues. IE

SELECT *
FROM [MYDB].[dbo].[FUNCTION]( DEFAULT, DEFAULT )
WHERE 'custom message' != 'Some message here'

What do you think? Will this cause a performance issue down the line?

2

It feels weird having nonsense filters for this purpose.

What about:

SELECT /* blarg */
    col1
,   col2
FROM blah;
3

I agree that it is weird. Please see my original post. I tried it that way first.

4

I was placing the comment inside the query.

5

No, not at all. A comparison of literal values will be pre-evaluated by the optimizer. If not true, it will likely just be ignored in the actual query plan.

For example:
WHERE 'a' <> 'b'
will just be essentially ignored.