[Lens] formula - clamp function min/max can be optional

[ghudgins]

Describe the feature: Make the lens formula clamp not require a min or max value.

Describe a specific use case for the feature:
When I have data that sometimes could generate negative values
And I don't want negative values
I need to use the clamp function
And I don't want to specify an arbitrarily high value...I want to not include a max value (like Canvas)
So I can get the visualization I want without having to use random constants

Note: if we go forward with this enhancement remember to update in app product documentation as that currently shows all fields required

Related discuss post

[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)

[stratoula]

This could simplify TSVB to Lens implementation too for 'positive_only' Here https://github.com/elastic/kibana/blob/main/src/plugins/vis_types/timeseries/public/trigger_action/metrics_helpers.ts#L207
and here https://github.com/elastic/kibana/blob/main/src/plugins/vis_types/timeseries/public/trigger_action/metrics_helpers.ts#L216
I am setting as max the metric value. It can be omitted with this enhancement.

[dej611]

I've digged a bit into this issue and found out some interesting insights:

• the clamp function in Canvas does not work when both min and max arguments are missing, despite the documentation saying otherwise

• in the tinymath clamp jsdoc documentation two more errors are described, which are somehow ignored by the Canvas tinymath documentation page.

  • I think the Canvas Tinymath documentation should be fixed to correctly reflect the clamp implemented behaviour.

• Omitting the max argument (i.e. clamp(myMetric, myOtherMetric)), makes the clamp function equivalent to the min function: min(myMetric, myOtherMetric)

• Omitting both the min and max argument (i.e. clamp(5)) makes it equivalent to the value itself

Perhaps the user experience can be improved by exposing some guidance to use the min function?

[flash1293]

@dej611 Unfortunately we can't use min or max because these names are taken by the Elasticsearch aggregations already. We could introduce clamp_min(metric, min) which behaves like the max tinymath function, what do you think?

[dej611]

It works.
Otherwise why not introduce a math_min/math_max functions?

[dej611]

I've put together a quick PoC with the following:

• Two new pick_min/_max operations that wraps the tinymath min/max functions. In the PoC they are just limited to 2 args for now.
• When using clamp with partial arguments, the correct pick_* operation is suggested in the error message

PoC: #132449

What do you think @flash1293 ?

[flash1293]

I like that approach 👍

[dej611]

Fixed by #132449