Any way to optimize the All value of a variable?

Dear all,
Thanks for you support on the following topic.

I have a dashboard linked to a MySQL data source in which there is a query based variable.
This variable can have, in some cases, hundreds of values so the All value gets translated into a very long IN (value1, value2, value3, … valueN) SQL condition.
This can easily become quite ineffective mainly when the value list is actually a partition of the whole set of data, in this case just removing the IN clause in the WHERE condition would lead to a much faster query.
Is there any way to modify the query based on the value of the dashboard variable?

I apologize if I was not clear and thank you for your time

Gaetano

You have still option to customize All value in the dashboard variable configuration. It can be for example *. Of course then you need update WHERE statement in the query - e.g. using regexp matching instead of IN operator and also you will need advance variable formatting, so generated query will have always correct SQL syntax.

Thank you! This is really smart, i tried it and it works very fine. How does this compare in terms of resource usage to the solution based on the list inclusion?