API Reference

Indexing functions

h3_geo_to_h3(`point`, resolution `int`) ⇒ `h3index`

Converts native PostgreSQL point to hex at given resolution.

``` SELECT h3_geo_to_h3(POINT('64.7498111652365,89.5695822308866'), 8);

h3_geo_to_h3

880326b88dfffff (1 row) ```

h3_to_geo(`h3index`) ⇒ `point`

Finds the centroid of this hex in native PostgreSQL point type.

``` SELECT h3_to_geo('880326b88dfffff');

h3_to_geo

(64.7498111652365,89.5695822308866) (1 row) ```

h3_to_geo_boundary(`h3index`) ⇒ `polygon`

Find the boundary of this hex, in native PostgreSQL polygon type.

``` SELECT h3_to_geo_boundary(:hexagon);

h3_to_geo_boundary

((89.5656359347422,64.3352882950961),...,(89.570369702947,64.104106930976)) (1 row) ```

Index inspection functions

h3_get_resolution(`h3index`) ⇒ `integer`

Returns the resolution of this hex.

``` SELECT h3_get_resolution(:hexagon), h3_get_resolution(:pentagon); h3_get_resolution | h3_get_resolution -------------------+------------------- 8 | 3 (1 row) ```

h3_get_base_cell(`h3index`) ⇒ `integer`

Returns the base cell number of the given hex.

``` SELECT h3_get_base_cell(:hexagon), h3_get_base_cell(h3_to_parent(:hexagon)); h3_get_base_cell | h3_get_base_cell ------------------+------------------ 2 | 2 (1 row) ```

h3_string_to_h3(`cstring`) ⇒ `h3index`

Converts the string representation to H3Index representation. Not very useful, since the internal representation can already be displayed as text for output, and read as text from input.

``` SELECT h3_string_to_h3('880326b88dfffff);

h3_string_to_h3

880326b88dfffff (1 row) ```

h3_to_string(`h3index`) ⇒ `cstring`

Converts the H3Index representation of the index to the string representation. Not very useful, since the internal representation can already be displayed as text for output, and read as text from input.

``` SELECT h3_to_string('880326b88dfffff);

h3_to_string

880326b88dfffff (1 row) ```

h3_is_valid(`h3index`) ⇒ `boolean`

Returns whether this is a valid hex.

``` SELECT h3_is_valid(:hexagon), h3_is_valid(:pentagon), h3_is_valid(:invalid); h3_is_valid | h3_is_valid | h3_is_valid -------------+-------------+------------- t | t | f (1 row)

```

h3_is_res_class_iii(`h3index`) ⇒ `boolean`

Returns true if the resolution of the given index has a class-III rotation, returns false if it has a class-II.

``` SELECT h3_is_res_class_iii(:hexagon), h3_is_res_class_iii(h3_to_parent(:hexagon)); h3_is_res_class_iii | h3_is_res_class_iii ---------------------+--------------------- f | t (1 row) ```

h3_is_pentagon(`h3index`) ⇒ `boolean`

Returns whether this represents a pentagonal cell.

``` SELECT h3_is_pentagon(:hexagon), h3_is_pentagon(:pentagon); h3_is_pentagon | h3_is_pentagon ----------------+---------------- f | t (1 row) ```

h3_get_faces(`h3index`) ⇒ `integer[]`

Find all icosahedron faces intersected by a given H3 index.

``` SELECT h3_get_faces('851c0047fffffff');

h3_get_faces

{11,6} (1 row) ```

Grid traversal functions

h3_k_ring(`h3index`, k `integer default 1`) ⇒ `setof`(`h3index`)

Returns all hexes within `k` (default 1) distance of the origin `hex`, including itself.

k-ring 0 is defined as the origin index, k-ring 1 is defined as k-ring 0 and all neighboring indices, and so on.

Output is provided in no particular order.

``` SELECT h3_k_ring('880326b88dfffff');

h3_k_ring

880326b88dfffff 880326b8ebfffff 880326b8e3fffff 880326b885fffff 880326b881fffff 880326b889fffff 880326b8c7fffff (7 rows) ```

h3_k_ring_distances(`h3index`, k `integer default 1`) ⇒ `setof`(index `h3index`, distance `integer`)

Finds the set of all hexes within `k` (default 1) distance of the origin `hex` and their respective distances, including itself.

Output rows are provided in no particular order.

``` SELECT * FROM h3_k_ring_distances(:hexagon); index | distance -----------------+---------- 880326b88dfffff | 0 880326b8ebfffff | 1 880326b8e3fffff | 1 880326b885fffff | 1 880326b881fffff | 1 880326b889fffff | 1 880326b8c7fffff | 1 (7 rows) ```

h3_hex_range(`h3index`, k `integer default 1`) ⇒ `setof`(`h3index`)

Returns all hexes within `k` (default 1) distance of the origin `hex`, including itself.

Output is sorted in increasing distance from origin. Will report an error if it encounters a pentagon, in this case use k_ring.

``` SELECT h3_hex_range(:hexagon);

h3_hex_range

880326b88dfffff 880326b8ebfffff 880326b8e3fffff 880326b885fffff 880326b881fffff 880326b889fffff 880326b8c7fffff (7 rows) ```

h3_hex_range_distances(`h3index`, k `integer default 1`) ⇒ `setof`(index`h3index`, distance `integer`)

Finds the set of all hexes within `k` (default 1) distance of the origin `hex` and their respective distances, including itself.

Output is sorted in increasing distance from origin. Will report an error if it encounters a pentagon, in this case use h3_k_ring.

``` SELECT * FROM h3_hex_range_distances(:hexagon); index | distance -----------------+---------- 880326b88dfffff | 0 880326b8ebfffff | 1 880326b8e3fffff | 1 880326b885fffff | 1 880326b881fffff | 1 880326b889fffff | 1 880326b8c7fffff | 1 (7 rows) ```

h3_hex_ranges(`h3index[]`, k `integer default 1`) ⇒ `setof`(`h3index`)

Returns all hexes within `k` (default 1) distance of every hex in the given array, including themselves.

Output is sorted in first by increasing order of elements in the array, secondly by distance of the particular element. Will report an error if it encounters a pentagon.

``` SELECT h3_hex_range(:hexagon), h3_hex_range('880326b8ebfffff'), h3_hex_ranges('{880326b88dfffff,880326b8ebfffff}'::h3index[]); h3_hex_range | h3_hex_range | h3_hex_ranges -----------------+-----------------+----------------- 880326b88dfffff | 880326b8ebfffff | 880326b88dfffff 880326b8ebfffff | 880326b8e9fffff | 880326b8ebfffff 880326b8e3fffff | 880326b8e1fffff | 880326b8e3fffff 880326b885fffff | 880326b8e3fffff | 880326b885fffff 880326b881fffff | 880326b88dfffff | 880326b881fffff 880326b889fffff | 880326b8c7fffff | 880326b889fffff 880326b8c7fffff | 880326b8c5fffff | 880326b8c7fffff | | 880326b8ebfffff | | 880326b8e9fffff | | 880326b8e1fffff | | 880326b8e3fffff | | 880326b88dfffff | | 880326b8c7fffff | | 880326b8c5fffff (14 rows) ```

h3_hex_ring(h3index[, k]) ⇒ `setof`(`h3index`)

Returns the hollow ring of hexes with `k` (default 1) distance of the origin `hex`.

Will report an error if it encounters a pentagon, in this case use h3_k_ring.

``` SELECT h3_hex_ring(:hexagon, 2);

h3_hex_ring

880326b8c1fffff 880326b8c5fffff 880326b8e9fffff 880326b8e1fffff 880326b8e7fffff 880326b8a9fffff 880326b8abfffff 880326b887fffff 880326b883fffff 880326b88bfffff 880326b8d5fffff 880326b8c3fffff (12 rows) ```

h3_distance(h3index, h3index) ⇒ `integer`

Determines the distance in grid cells between the two given indices.

``` SELECT h3_distance('880326b881fffff', '880326b885fffff');

h3_distance

``````       1
``````

(1 row) ```

EXPERIMENTALS

Hierarchical grid functions

h3_to_parent(h3index[, parentRes]) ⇒ `h3index`

Returns the parent (coarser) hex containing this `hex` at given `parentRes` (if no resolution is given, parent at current resolution minus one is found).

``` SELECT h3_to_parent('880326b88dfffff', 5);

h3_to_parent

850326bbfffffff (1 row) ```

h3_to_children(h3index[, childRes]) ⇒ `setof`(`h3index`)

Returns all hexes contained by `hex` at given `childRes` (if no resolution is given, children at current resolution plus one is found).

May cause problems with too large memory allocations. Please see `h3_to_children_slow`.

``` SELECT h3_to_children('880326b88dfffff', 9);

h3_to_children

890326b88c3ffff 890326b88c7ffff 890326b88cbffff 890326b88cfffff 890326b88d3ffff 890326b88d7ffff 890326b88dbffff (7 rows) ```

h3_to_children_slow(h3index[, childRes]) ⇒ `setof`(`h3index`)

This functions does the same as `h3_to_children_slow` but allocates smaller chunks of memory at the cost speed.

h3_compact(h3index[]) ⇒ `setof`(`h3index`)

Returns the compacted version of the input array. I.e. if all children of an hex is included in the array, these will be compacted into the parent hex.

``` SELECT h3_compact(array_cat(ARRAY(SELECT h3_to_children('880326b88dfffff')), ARRAY(SELECT h3_to_children('880326b88bfffff'))));

h3_compact

880326b88bfffff 880326b88dfffff (2 rows) ```

h3_uncompact(`h3index[]` resolution `integer default -1`) ⇒ `setof`(`h3index`)

Uncompacts the given hex array at the given resolution. If no resolution it will be chosen to be the highest resolution of the given indexes + 1.

``` SELECT h3_uncompact(array_cat(ARRAY(SELECT h3_to_parent('880326b88dfffff')), '{880326b88bfffff}'::h3index[]));

h3_uncompact

890326b8803ffff ... 890326b88bbffff (56 rows) ```

Region functions

h3_polyfill(exterior `polygon`, holes `polygon[]`, resolution `integer`) ⇒ `setof`(`h3index`)

Polyfill takes a given exterior native postgres polygon and an array of interior holes (also native polygons), along with a resolutions and fills it with hexagons that are contained.

``` SELECT h3_polyfill(exterior, holes, 1) FROM ( SELECT * FROM h3_set_to_linked_geo(ARRAY(SELECT h3_to_children('8059fffffffffff, 1))) ) q;

h3_polyfill

8158fffffffffff 8159bffffffffff 8158bffffffffff 81597ffffffffff 81587ffffffffff 81593ffffffffff 81583ffffffffff (7 rows) ```

h3_set_to_linked_geo(`h3index[]`) ⇒ `setof`(exterior `polygon`, holes `polygon[]`)

Create records of exteriors and holes.

``` SELECT h3_polyfill(exterior, holes, 1) FROM ( SELECT * FROM h3_set_to_linked_geo(ARRAY(SELECT h3_to_children('8059fffffffffff, 1))) ) q;

h3_polyfill

8158fffffffffff ... 81583ffffffffff (7 rows) ```

Unidirectional edge functions

Unidirectional edges are a form of H3Indexes that denote a unidirectional edge between two neighbouring indexes.

h3_indexes_are_neighbors(`h3index`, `h3index`) ⇒ `boolean`

Determines whether or not the two indexes are neighbors. Returns true if they are and false if they aren't

``` SELECT h3_indexes_are_neighbors(:hexagon, '880326b8ebfffff'), h3_indexes_are_neighbors('880326b881fffff', '880326b8ebfffff'); h3_indexes_are_neighbors | h3_indexes_are_neighbors --------------------------+-------------------------- t | f (1 row) ```

h3_get_h3_unidirectional_edge(origin `h3index`, destination `h3index`) ⇒ `h3index`

Returns the edge from origin to destination

Will error if the two indexes are not neighbouring

``` SELECT(h3_get_h3_unidirectional_edge(:hexagon, :neighbour));

h3_get_h3_unidirectional_edge

1180326b885fffff (1 row) ```

h3_unidirectional_edge_is_valid(`h3index`) ⇒ `boolean`

Returns true if the given hex is a valid edge.

``` SELECT h3_unidirectional_edge_is_valid(h3_get_h3_unidirectional_edge(:hexagon, :neighbour));

h3_unidirectional_edge_is_valid

t (1 row) ```

h3_get_origin_h3_index_from_unidirectional_edge(`h3index`) ⇒ `h3index`

Returns the origin index from the given edge

``` SELECT h3_get_origin_h3_index_from_unidirectional_edge(h3_get_h3_unidirectional_edge(:hexagon, :neighbour)), :hexagon; h3_get_origin_h3_index_from_unidirectional_edge | ?column? ----------------------------------------------+----------------- 880326b885fffff | 880326b885fffff (1 row) ```

h3_get_destination_h3_index_from_unidirectional_edge(`h3index`) ⇒ `h3index`

Returns the destination index from the given edge

``` SELECT h3_get_destination_h3_index_from_unidirectional_edge(h3_get_h3_unidirectional_edge(:hexagon, :neighbour)), :neighbour; h3_get_destination_h3_index_from_unidirectional_edge | ?column? ---------------------------------------------------+----------------- 880326b887fffff | 880326b887fffff (1 row) ```

h3_get_h3_indexes_from_unidirectional_edge(`h3index`) ⇒ (origin `h3index`, destination `h3index`)

Returns both the origin and destination indexes from the given edge

``` SELECT * FROM h3_get_h3_indexes_from_unidirectional_edge(h3_get_h3_unidirectional_edge(:hexagon, :neighbour)); origin | destination -----------------+----------------- 880326b885fffff | 880326b887fffff (1 row) ```

h3_get_h3_unidirectional_edges_from_hexagon(`h3index`) ⇒ `setof`(`h3index`)

Returns the set of all valid unidirectional edges with the given origin

``` SELECT h3_get_h3_unidirectional_edges_from_hexagon(:hexagon);

h3_get_h3_unidirectional_edges_from_hexagon

1180326b885fffff 1280326b885fffff 1380326b885fffff 1480326b885fffff 1580326b885fffff 1680326b885fffff (6 rows) ```

h3_get_h3_unidirectional_edge_boundary(`h3index`) ⇒ `polygon`

Find the boundary of this edge, in native PostgreSQL polygon type.

``` SELECT h3_get_h3_unidirectional_edge_boundary(h3_get_h3_unidirectional_edge(:hexagon, :neighbour));

h3_get_h3_unidirectional_edge_boundary

((89.5830164946548,64.7146398954916),(89.5790678021742,64.2872231517217)) (1 row) ```

Miscellaneous H3 functions

h3_hex_area_km2(resolution `integer`) ⇒ `float`

Returns the area of an hex in square kilometers at the given resolution.

``` SELECT h3_hex_area_km2(10);

h3_hex_area_km2

``````0.0150475
``````

(1 row) ```

h3_hex_area_m2(resolution `integer`) ⇒ `float`

Returns the area of an hex in square meters at the given resolution.

``` SELECT h3_hex_area_m2(10);

h3_hex_area_m2

`````` 15047.5
``````

(1 row) ```

h3_edge_length_km(resolution `integer`) ⇒ `float`

Returns the length of the edges of an hex in kilometers at the given resolution.

``` SELECT h3_edge_length_km(10);

h3_edge_length_km

``````0.065907807
``````

(1 row) ```

h3_edge_length_m(resolution `integer`) ⇒ `float`

Returns the length of the edges of an hex in meters at the given resolution.

``` SELECT h3_edge_length_m(10);

h3_edge_length_m

65.90780749 (1 row) ```

h3_num_hexagons(resolution `integer`) ⇒ `bigint`

Returns the number of unique indexes at the given resolution

``` SELECT h3_num_hexagons(15);

h3_num_hexagons

569707381193162 (1 row) ```

h3_get_res_0_indexes() ⇒ `setof`(`h3index`)

Returns all 122 basecells.

``` SELECT h3_get_res_0_indexes();

h3_get_res_0_indexes

... (122 rows) ```

PostGIS integration

We provide some simple wrappers for casting to PostGIS types.

h3_geo_to_h3(geometry / geography, resolution) ⇒ `h3index`

The `h3_geo_to_h3` function has been overloaded to support both PostGIS `geometry` and `geography`.

h3_to_geometry(`h3index`) ⇒ `geometry`

Finds the centroid of this hex as PostGIS geometry type.

``` SELECT h3_to_geometry('8a63a9a99047fff');

h3_to_geometry

0101000020E61000008BE4AED877D54B40C46F27D42B2F2940 (1 row) ```

h3_to_geography(`h3index`) ⇒ `geography`

Same as above, but returns `geography` type.

h3_to_geo_boundary_geometry(`h3index`) ⇒ `geometry`

Find the boundary of this hex, as PostGIS type.

``` SELECT boundary_geometry('8a63a9a99047fff');

boundary_geometry

0103000020...FB70D54B40 (1 row) ```

h3_to_geo_boundary_geography(`h3index`) ⇒ `geography`

Same as above, but returns `geography` type.

Functions without bindings

Some functions does not have bindings:

• `degsToRads`/`radsToDegs`: Use postgres built-ins `RADIANS()` and `DEGREES()` instead.
• Memory handling functions: `maxKringSize`, `h3LineSize`, `maxH3ToChildrenSize`, `maxUncompactSize`, `maxPolyfillSize`, `destroyLinkedPolygon`. Memory is handled by the extensnion.