Various fixes to spatial functions (ST_ENVELOPE and ST_NPOINTS)

[craigtaverner]

Various fixes to spatial functions:

• Made ST_ENVELOPE multi-value aware
• Added ST_NPOINTS
• Refactored doc-values support (so ST_ENVELOPE, ST_NPOINTS and all geogrid functions are similar)
• Supported doc-values in ST_X/Y and ST_XYMAX/MIN
• Support multi-values in ST_X/YMAX/MIN

This last point is interesting. Because ST_X and ST_Y use @ConvertEvaluator, they support multi-values by converting each internal value, which makes sense for points, since we cannot collect points into a MultiPoint and perform ST_X/ST_Y on the multipoint. However, for ST_XMAX, ST_XMIN, ST_YMAX and ST_YMIN we can follow the convention we are using elsewhere in spatial functions, and collect the multi-values into a geometry collection. This means that, for example, ST_XMAX(field) will return the maximum x value for all values in the multi-value, whether they are points, shapes or a mixture.

Checklist:

• Make ST_ENVELOPE multi-value aware (so we get envelopes of multi-points, and geometry collections)
• Add ST_NPOINTS and make it multi-value aware
• Make these two and all geogrid functions similarly doc-values enabled
• Expand csv-tests (spatial.csv-spec for multi-point, and spatial_shapes.csv_spec for shapes)
• Expand PhysicalPlanOptimizerTests to verify all doc-values combinations work
• Support doc-values in ST_X, ST_Y, ST_XMAX, etc.
• Support multivalues for ST_XMAX, ST_XMIN, ST_YMAX, ST_YMIN as geometry collections
• Link ST_NPOINTS into docs
• Update docs related to multi-values in spatial types

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[elasticsearchmachine]

Hi @craigtaverner, I've created a changelog YAML for you.

[github-actions]

🔍 Preview links for changed docs

• docs/reference/query-languages/esql/kibana/docs/functions/st_npoints.md

[github-actions]

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[elasticsearchmachine]

Hi @craigtaverner, I've updated the changelog YAML for you.