ST_H3CellIDs

Introduction: Cover the geometry by H3 cell IDs with the given resolution(level). To understand the cell statistics please refer to H3 Doc H3 native fill functions doesn't guarantee full coverage on the shapes.

Cover Polygon

When fullCover = false, for polygon sedona will use polygonToCells. This can't guarantee full coverage but will guarantee no false positive.

When fullCover = true, sedona will add on extra traversal logic to guarantee full coverage on shapes. This will lead to redundancy but can guarantee full coverage.

Choose the option according to your use case.

Cover LineString

For the lineString, sedona will call gridPathCells(https://h3geo.org/docs/api/traversal#gridpathcells) per segment. From H3's documentation

This function may fail to find the line between two indexes, for example if they are very far apart. It may also fail when finding distances for indexes on opposite sides of a pentagon.

When the gridPathCells function throw error, Sedona implemented in-house approximate implementation to generate the shortest path, which can cover the corner cases.

Both functions can't guarantee full coverage. When the fullCover = true, we'll do extra cell traversal to guarantee full cover. In worst case, sedona will use MBR to guarantee the full coverage.

If you seek to get the shortest path between cells, you can call this function with fullCover = false

Format: ST_H3CellIDs(geom: geometry, level: Int, fullCover: true)

Since: v1.5.0

Example:

SELECT ST_H3CellIDs(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'), 6, true)

Output:

+----+--------------------------------+
| op |                         EXPR$0 |
+----+--------------------------------+
| +I | [605547539457900543, 605547... |
+----+--------------------------------+