[Maps] Support custom filtering of buckets in geogrid aggregation visualizations

[talevy]

Describe the feature:

Enable a way for filtering buckets visualized in a map's
grid visualization.

This can potentially be implemented by
adding an additional bucket-selector pipeline aggregation to the ES query.

Describe a specific use case for the feature:

Sometimes it may be necessary to hide buckets in a map's
grid aggregation from showing buckets with a certain count.

elastic/elasticsearch#50480 describes a scenario where
it would be nice to have min_doc_count as
an additional parameter to a visualization so one can filter out
buckets that have a lower count than this.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[thomasneirynck]

If I understand correctly, there are two possible asks:

• just support filtering on min-count: min_doc_count is a "special" property, and can be applied to any bucket (now also geo_tile, which Maps is using for grid-sources). The Maps-UX could provide an option to set this param (similar to how in Visualize users can edit the "advanced json" and insert this filter there).
• support any kind of filter: a more generic solution is to provide some UX for people to apply a custom bucket selector script. This is a more generic solution that could also be used to write a filter that's identical to setting min_doc_count: n.

[talevy]

support any kind of filter: a more generic solution is to provide some UX for people to apply a custom bucket selector script. This is a more generic solution that could also be used to write a filter that's identical to setting

correct, this second bullet point is the one I am suggesting as a way to implement this feature request.

[thomasneirynck]

adding 7.16 label on this. cc @nreese . adding equivalent of min_doc_count to Maps metric-aggs would close functional gap with region/coordinate-map.

[thomasneirynck]

wrt deprecations of old visualizations. This is a small gap, without a clear view of how many users would run into it. Can always pick up later if necessary, as we get feedback from users trying to upgrade.

[thomasneirynck]

discussed offline. There's a narrow way of looking at: ie. supporting the equivalent functionality of setting the min_doc_count-param in the legacy tile_map and region_map visualizations. Closing this is what triggered adding the 7.16/8.0 labels.

The other one - supporting any bucket-filtering script - is broader, and out of scope.

Given that the narrow-case is niche, removing the target version-labels.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)