[Lens] Implement counter rate expression

[mbondyra]

Summary

Fixes #46627

Adds lens_counter_rate function.

The counter rate function works exactly like derivative expression if value increases or is equal to previous one – it returns the difference between current and previous value.

If value decreased compared to the previous value, the function outputs the current value. Here's the example:

input	output	comment
1	undefined	previous value doesn't exist
5	4	increasing dif(5-1)
11	6	increasing dif(11-5)
4	4	decreasing diff, so the counter is reset to the value
4	0	dif(4-4)

Special cases

For undefined:

input	output	comment
1	undefined	previous value doesn't exist
5	4	increasing dif(5-1)
undefined	undefined	undefined current value
3	undefined	undefined previous value

Question: NaN case

Should value after NaN be also NaN (eg. counter between NaN and 2 - that's what derivative do) or should it be NaN?

input	output	comment
1	undefined	previous value doesn't exist
3	2	increasing dif(3-1)
{} (converted to NaN)	NaN
2	2 or NaN??	**This is the doubt**
3	1	increasing diff (3-2)

The expression takes inputColumnId, outputColumnId, outputColumnName, by (similar behavior to new expression time series functions)

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[flash1293]

Should value after NaN be also NaN (eg. counter between NaN and 2 - that's that derivative do) or should it be NaN?

Good question, I think going with 2 is fine, because it's assuming broken data in the previous bucket so we are recovering as much as possible from the value in the next bucket (just like the "smaller than previous value" case)

[lukeelmers]

Relocating series_calculation_helpers outside of the specs directory makes sense to me, so I'm good on the app arch changes once we get a green build 👍

[flash1293]

Didn't run, but test cases look good to me. Left one small nit

[flash1293]

nit: There are four places where currentValue is cast to number, we could refactor this to a single currentValueAsNumber, but no biggie

[wylieconlon]

I didn't run this code, but just looking at the code looks good. Left one comment about clarifying a test case.

[wylieconlon]

Most of the other tests are using numbers that are always increasing, this test appears to be the only one that tests the scenario where the number goes down. Are there other scenarios to test around the edge cases of the algorithm? Or maybe you can name the test differently to indicate that this one tests 2 things?

[mbondyra]

Good idea @wylieconlon! I'll add new test.

[mbondyra]

@elasticmachine merge upstream

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 483988c

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
lens	911.0KB	910.4KB	-567.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
expressions	181.4KB	182.3KB	+862.0B
lens	50.3KB	50.6KB	+238.0B
total			+1.1KB

History

• 💔 Build #87290 failed c7cb0bc
• 💔 Build #87294 failed c7e646a
• 💚 Build #87130 succeeded 068c5fd
• 💚 Build #87017 succeeded 31d0640
• 💔 Build #87015 failed 30b1eb7

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@elasticmachine merge upstream