Improve handling of very small slices in pie charts

[gmoskovicz]

Kibana version: 6.2

Elasticsearch version: 6.2

Server OS version: Any

Browser version: Any

Browser OS version: Any

Original install method (e.g. download page, yum, from source, etc.): Zip

Description of the problem including expected versus actual behavior:

In 5.x you were able to see very small buckets as lines, but in 6.x all very small buckets are just missing, and you see a big white space now.

Steps to reproduce:

1. Create a Pie Chart visualization with 1000 buckets.
2. Run and check results.

5.x Results

6.x results

This is just an example, but when you have a relevant chart, in 6.x you can no longer see the very small buckets that we use to be able to see, and just see the following:

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

No logs.

[timroes]

We have some issues handling very small slices in pie charts and should think about how we properly want to handle them.

Users that create too manys lices might end up with slices below a pixel, that won't even be drawn anymore. It might get worse in cases where you have this very small slices only on the second level of the pie chart. In those cases it might look like there is no second level at all because all slices are below a pixel width.

We should find a generic approach to handle that many/small slices in a good way for users (or limit slice amount, and sizes in a user friendly way).

[stratoula]

The new chart implementation will solve this. For example a multi buckets pie chart will be displayed as: