[Discover] Add a warning and tooltip for _score column in the grid

[jughosta]

For the legacy view we used to have a tooltip which was explaining how to get _score values. Would be great to introduce it to the grid view too.

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[shardulgawande27]

/attempt #167271

[shardulgawande27]

@jughosta @kertal could you explain step to get _score values.

[kertal]

you don't need the _score values, you need to display the warning when the column is named _score, and it's not sorted by _score

kibana/src/plugins/discover/public/components/doc_table/components/table_header/table_header_column.tsx

Lines 84 to 86 in 1a213bd

	// If this is the _score column, and _score is not one of the columns inside the sort, show a
	// warning that the _score will not be retrieved from Elasticsearch
	const showScoreSortWarning = name === '_score' && !curColSort;

[davismcphee]

@kertal should you comment refer to _score instead of _source?

[kertal]

@kertal exactly, it's _score not _source. edited, thx

[rbrtj]

Hey!
Should we disable the column token when a warning is displayed?
@kertal

Also, do you see this as custom behavior for UnifiedDataTable or just an override coming from DiscoverGrid?

[kertal]

thx @rbrtj for you questions

@l-suarez will have a look from design side, to figure out about the columns token (which should just be used for the _score. We show it because without sorting by _score, no _score value is calculated and this is not very obvious to the user)

Also, do you see this as custom behavior for UnifiedDataTable or just an override coming from DiscoverGrid?

We discussed this and we're fine with adding this as a custom behavior to the UnifiedDataTable, but it just needs to bedisplayed if sorting is allowed, else it doesn't make sense.

[l-suarez]

@jughosta @kertal out of curiosity, would it make sense that we sort the column for the user if they want to display _score? asking them to sort by the column is an extra step if they really want to use the field.

[kertal]

yes, I think being more helpful to the user in this case makes sense, but this ain't a papercut then, it has more complex state manipulation, so I think as a first step adding a warning ... or an info is fine, and then: let's improve it 👍

[l-suarez]

Agree. Let's do this as a paper-cut, we don't need the token for _score, keeping the warning icon

[davismcphee]

Sorting _score by default probably makes sense, but a user could still manually unsort it, so agreed that the warning would still be helpful.