Discover fetches date histogram even when no documents match the query

[lukasolson]

Describe the bug:

The unified histogram fetches the date histogram even when there are no results.

Steps to reproduce:

1. Open Discover
2. Use a query that produces no results
3. Notice that two queries are made - one for the documents & one for the histogram

Ironically, if you refresh the entire browser, only one request is made (for the documents). But each time you click the "refresh" button, you get two additional queries.

Expected behavior:

Only one query for the documents.

Screenshots (if relevant):

Screen.Recording.2024-10-30.at.4.34.44.PM.mov

Any additional context:

Probably related to #165192.

[elasticmachine]

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

[jughosta]

Agree, this might be not ideal but I think it's working as expected. We make requests not in a sequence but in parallel to render the content as soon as we get the response for either the table or the histogram.

[kertal]

@jughosta is right, it's working as expected. The aim was to execute those queries in parallel to show results ASAP. Closing therefore

[lukasolson]

Talked with @davismcphee about this one to make sure I understood what was happening - I was confused that when you load Discover from scratch, we only ever got one request for the documents. It seems there's an (intentional) race condition, and when you load Discover, by the time Lens loads, we already have the response from the documents query, so we don't run the histogram query, but when you just click "refresh" it makes both requests in parallel, and cancels the histogram query if the documents query comes back empty.