[TSVB] Replace indexpattern input text with a combobox

[stratoula]

Describe the feature:
Right now, if a user wants to use a non-default index pattern on TSVB, she should type the name exactly as it is. There is no way for the user to search and choose from the existing ones. This is a bad UX as the user should remember the index pattern which is quite difficult especially if there are many index patterns.

We would like to change this and replace the simple input text with a combobox where the user could either choose from the list of index patterns or type freely the index pattern she wants.

[elasticmachine]

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

[alexwizp]

@stratoula do you think how we should support user input for multiple indexes?

My curiosity was caused by this issue #82438. If in the future we want to use SearchSource in TSVB, then it probably makes sense to allow users to enter only one index. On the other hand TSVB works fine with several low-level indexes splitted by comma

IMO for now the best option should looks like:

but how it's related to our plans?

@timroes any ideas?

[stratoula]

I don't think that we should change the current way that TSVB works for now so I think that what you propose is the right way that we should go. About supporting index patterns on TSVB it is something that is under discussion and imho we shouldn't do such a huge change on TSVB. I would love Tim's feedback on this though.

[timroes]

We should imho only allow a single selection in the searchbox. The user can still enter an index pattern using comma as mentioned above, but there will be (especially when we leverage information from the index patterns) be a huge difference between using two index patterns or one with comma separated. Thus I think this combobox should be single selection only.

[alexwizp]

@timroes I don't understand a benefits of your approach. In case if user decided to select 2 indexes he/she doesn't have any way to do without typing value using keyboard. Single selection mode overrides the previous value.

I suggest to allow users to input custom index patterns if they need it and think about using multi selection mode. From my point of view it's right from the UX perspective.

You can test how it works here: #82696

[timroes]

I agree that this might from a user perspective be the better solution, I just don't think we should do it before we're not having a clearer vision for index patterns in Kibana. The order of indexes in an index pattern matters to finding it later (i.e. the indexpattern foo-*,bar-* can be a different one than bar-*,foo-*). Since I suspect that we'll need to make some matching on those if we would go into index patterns in TSVB, I find it missleading showing them as foo-* bar-*, since we hide an explicit order more - I am not even sure if the combobox guarantees us an order of the tags in general.

Also it would rise the question if we would want to split tags by "index pattern" later or by index, i.e. would we have foo-* bar-* baz-* or foo-*,baz-* bar-* in case that foo-*,baz-* index pattern exists.

So I am not saying that we should never go into the split solution, but I would prefer postponing that change in design until we're further with our plan around index patterns and until then keep the "input" as close to what we currently have, i.e. just one text, no visual splitting for the user.

[stratoula]

When this #91367 is impemented, I think we should close this issue
cc @alexwizp