H3_GET_RESOLUTION

Return the H3 hierarchy resolution of a cell as an integer 0 through 15.

Category: h3Returns: INTDialect: Standard

Syntax

H3_GET_RESOLUTION(cell)

Description

## Overview Returns the resolution (level in the H3 hierarchy) of the given cell as an integer in the range 0 through 15. Every H3 cell carries its resolution in the low bits of its ID; this function extracts it directly without any computation or I/O. It is the cheapest way to find out what level a cell occupies and is used throughout H3 pipelines to validate inputs, partition queries, and roll cells up to a common comparison level. Use it whenever you accept H3 input from a user, from storage, or from a join where the resolution may vary. ## Behavior - Returns an INT in the range [0, 15]. - Returns NULL if the input is NULL or not a valid H3 cell index. - The operation is O(1): the resolution is encoded directly in the cell ID. - Deterministic: the same cell always returns the same resolution. - Both hexagon and pentagon cells report a resolution from 0 to 15; the pentagon flag is separate (see H3_IS_PENTAGON). ## H3 resolution reference | Res | Average edge length | Average hex area | | --- | --- | --- | | 0 | 1,107 km | 4.25 million km^2 | | 4 | 22.6 km | 1,770 km^2 | | 7 | 1.22 km | 5.16 km^2 | | 9 | 174 m | 0.11 km^2 | | 12 | 9.4 m | 307 m^2 | | 15 | 0.5 m | 0.9 m^2 | ## Compatibility - Follows the standard H3 hierarchical hex grid specification for resolution extraction.

Parameters

Name	Type	Description
`cell`		Specifies the H3 cell index whose resolution to return. Must be a valid H3 cell.

Examples

-- Expect 9.
SELECT H3_GET_RESOLUTION(H3_LATLNG_TO_CELL(51.5074, -0.1278, 9)) AS res;

-- Check for mixed-resolution contamination in a supposedly res-9 column.
SELECT H3_GET_RESOLUTION(h3_cell) AS res, COUNT(*) AS n
FROM analytics.curated.h3_events_res9
GROUP BY H3_GET_RESOLUTION(h3_cell)
ORDER BY res;

-- Keep only resolution 7 cells from a heterogeneous ingest.
SELECT cell_id
FROM spatial.reference.h3_cells
WHERE H3_GET_RESOLUTION(cell_id) = 7;

-- Roll every cell up to a shared resolution 5 for comparison.
SELECT event_id,
       H3_CELL_TO_PARENT(h3_cell, 5) AS h3_res5
FROM analytics.curated.h3_events_mixed
WHERE H3_GET_RESOLUTION(h3_cell) >= 5;

Pitfalls

Mixed-resolution H3 columns cause silent join errors because cells at different resolutions are distinct integers that never match. Always validate resolution when accepting H3 cells from external sources.
The function does not distinguish pentagon cells; resolutions 0 through 15 are reported for both hexagons and pentagons. Use H3_IS_PENTAGON for the pentagon check.
Do not compare two cells' resolutions as a proxy for geographic proximity. Two cells at resolution 9 can be on opposite sides of the globe.
NULL or invalid cells return NULL silently. Validate with H3_IS_VALID_CELL when cells come from untrusted sources.
Odd-numbered resolutions are Class III (see H3_IS_RES_CLASS_III) and are rotated relative to their even-numbered parents; this affects rendering and cell orientation but not the resolution number itself.