[TSVB2Lens] Support top_hit of size 1 aggregation

[stratoula]

Summary

Part of #125539

It adds support for TopHit aggregations with size 1. The layer is translated to a quick function last_value.

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

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

[mbondyra]

Quick question - you chose to convert it to formula, why not last_value quick function? That would give the extra option to pass Order by -> Sort by date field. Also, I am wondering maybe we should block support when the order is set to ascending, because in Lens we only support last value but not first value (so when we have sorting order set to ascending the chart is different)

Apart from that, why they differ so much? I do not understand 😅 EDIT- I do understand now, it's the time interval that is different (second image corrects it)

dash.ndjson.zip

[flash1293]

@mbondyra The Lens one is using 3 hour buckets, the tsvb is using 4 hour buckets due to the different "auto" interval behavior.

[flash1293]

Agree about using the quick function for this if possible would be better to stay consistent.

Also, I know I came up with this idea but I realized it's actually not completely identical - TSVB is able to handle last value of a multi value by using the provided aggregation function, but Lens will show a warning. I think it's still fine to do this conversion as there are other small differences, just wanted to note.

[stratoula]

@elasticmachine merge upstream

[stratoula]

@mbondyra @flash1293 I replaced it to work with the quick function and not allow it for asc.I don't have a strong opinion on supporting this transaction or not. It works only for size 1, order desc and displays a warning in Lens for multi values.
I see advantages on supporting it but I agree that it might not add great value to the feature :)
Whatever you want, I am comfortable with both options (supporting or not supporting)

[mbondyra]

Retested and works as expected. I don't have a strong opinion too, just wondering. I think what would help is if we add this option in Lens, if users actually use it :)

[kibana-ci]

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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	1.1MB	1.1MB	+34.0B
visTypeTimeseries	462.2KB	462.7KB	+495.0B
total			+529.0B

History

• 💛 Build #24580 was flaky b57c6c1

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@elasticmachine merge upstream

[stratoula]

Ok I will merge it then :) I don't think that it hurts anyone even if it might support very few TSVB to Lens transitions :)