Optional Parameters Support

Today to make a parameter optional, the user needs to have a workaround in the query logic itself. For example:

select count(0)
from queries
where 'All' = '{{org_id}}' or org_id::varchar = '{{org_id}}'

In this case when the value of org_id is All, then we don’t filter by it. It will be great if the user could mark a whole section as optional if no parameter is provided. The templating language we use (Mustache) actually supports this:

select count(0)
from queries
{{#org_id}}
where 'All' = '{{org_id}}' or org_id::varchar = '{{org_id}}'
{{/org_id}}

If no value for {{org_id}} is provided, then the section between {{#org_id}} and {{/org_id}} won’t be rendered. So in theory, we can just allow for passing empty values for parameters and it works.

This has two issues though:

1. Any false-y value will make this section not render. Including 0 (zero), which might be acceptable in some cases.
2. This might make the implementation of #2904 more complicated.

We should probably take this into account when implementing #2904, and revisit once it’s indeed implemented.

[smick]

Metabase solved this using bracket syntax: [[AND created >= {{start_date}} ]].

If the variable referenced within the double brackets (start_date) exists then the contents of the brackets is parsed into the query, otherwise the line is ignored.

This is quite elegant in my opinion and it doesn’t invite users to abuse default values.

[renekyewski]

Any news? This is pretty critical for us.