Support spatial distance search in ES|QL (ST_DWITHIN, ST_DISTANCE)

[craigtaverner]

Description

The Elasticsearch _search API supports distance filtering and sorting:

• Sorting using the _geo_distance sort field
• Filtering using geo_distance

In PostGIS there are two related functions:

• ST_DWITHIN for filtering by distance
• ST_DISTANCE for calculating a distance, also usable for sorting

These features can be implemented in ES|QL through two overlapping OGC compliant functions:

• boolean ST_DWITHIN(geomA, geomB, distance) for filtering by distance
• float ST_DISTANCE(geomA, geomB) for calculating a distance, filtering and sorting

Sorting example:

FROM airports
| EVAL distance = ST_DISTANCE(location, TO_GEOPOINT("POINT(12 55)", 500000)
| SORT distance ASC
| LIMIT 10

See the PostGIS documentation for inspiration:

• https://postgis.net/docs/ST_Distance.html
• https://postgis.net/docs/ST_DWithin.html

Tasks

Beta Give feedback

1. Review existing Elasticsearch support for distance filtering and sorting
2. Review PostGIS and OGC specifications for these functions
3. Implement raw ST_DISTANCE function
4. Implement raw ST_DWITHIN function
5. Support distance filtering with both functions
6. Support Lucene push-down for distance filtering
7. Support sorting by distance
8. Support Lucene push-down for sorting by distance
9. Documentation

[elasticsearchmachine]

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

[craigtaverner]

We should also keep in mind use cases involving speed, as discussed at #108332 (comment)