h3 0.3.0

This Release
h3 0.3.0
Date
Status
Stable
Latest Stable
h3 1.0.5 —
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Abstract
PostgreSQL bindings for H3
Released By
bytesandbrains
License
The Apache License, Version 2.0, January 2004
Special Files

Extensions

h3 0.3.0
PostgreSQL bindings for H3

README

H3 bindings for PostgreSQL

An extension for PostgreSQL that provides bindings for the H3 indexing system.

Installation

First, you must build H3.

git clone https://github.com/uber/h3.git cd h3 cmake -DCMAKE_C_FLAGS=-fPIC . make sudo make install

Then build h3-pg:

git clone ... cd h3-pg make sudo make install

Run psql and load/use extension in database:

``` CREATE_EXTENSION h3;

SELECT h3_h3_to_children('880326b88dfffff', 9);

h3_h3_to_children

890326b88c3ffff 890326b88c7ffff 890326b88cbffff 890326b88cfffff 890326b88d3ffff 890326b88d7ffff 890326b88dbffff ```

Development

We provide a Dockerfile for development without installation of H3 and Postgres. The following requires that your system has docker installed.

First, build the docker image:

docker build -t h3-pg .

Then, build the extension and run the test suite:

docker run --rm h3-pg

Afterwards, to quickly build and test changes, run:

chmod -R 777 . docker run --rm -it -v "$PWD":/tmp/h3-pg h3-pg

It will mount the code as a volume, and also mount the test output directory, so output can be inspected. The chmod might be needed if you get permission denied errors.

Usage

Generally all functions have been renamed from camelCase to snake_case with an added h3*prefix. This means a few functions will have a doubleh3*h3* prefix, but we chose this for consistency. For example h3ToChildren becomes h3_h3_to_children.

Indexing functions

h3_geo_to_h3(point, resolution) returns 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_h3_to_geo(h3index) returns point

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

``` SELECT h3_h3_to_geo('880326b88dfffff');

h3_h3_to_geo

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

h3_h3_to_geo_boundary(h3index) returns polygon

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

``` SELECT h3_h3_to_geo_boundary(:hexagon);

h3_h3_to_geo_boundary

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

Index inspection functions

h3_h3_get_resolution(h3index) returns integer

Returns the resolution of this hex.

SELECT h3_h3_get_resolution(:hexagon), h3_h3_get_resolution(:pentagon); h3_h3_get_resolution | h3_h3_get_resolution -------------------+------------------- 8 | 3 (1 row)

h3_h3_get_base_cell(h3index) returns integer

Returns the base cell number of the given hex.

SELECT h3_h3_get_base_cell(:hexagon), h3_h3_get_base_cell(h3_h3_to_parent(:hexagon)); h3_h3_get_base_cell | h3_h3_get_base_cell ------------------+------------------ 2 | 2 (1 row)

h3_string_to_h3(cstring) returns 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_h3_to_string(h3index) returns 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_h3_to_string('880326b88dfffff);

h3_h3_to_string

880326b88dfffff (1 row) ```

h3_h3_is_valid(h3index) returns boolean

Returns whether this is a valid hex.

``` SELECT h3_h3_is_valid(:hexagon), h3_h3_is_valid(:pentagon), h3_h3_is_valid(:invalid); h3_h3_is_valid | h3_h3_is_valid | h3_h3_is_valid -------------+-------------+------------- t | t | f (1 row)

```

h3_h3_is_res_class_iii(h3index) returns 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_h3_is_res_class_iii(:hexagon), h3_h3_is_res_class_iii(h3_h3_to_parent(:hexagon)); h3_h3_is_res_class_iii | h3_h3_is_res_class_iii ---------------------+--------------------- f | t (1 row)

h3_h3_is_pentagon(h3index) returns boolean

Returns whether this represents a pentagonal cell.

SELECT h3_h3_is_pentagon(:hexagon), h3_h3_is_pentagon(:pentagon); h3_h3_is_pentagon | h3_h3_is_pentagon ----------------+---------------- f | t (1 row)

Grid traversal functions

h3_k_ring(h3index[, k]) returns 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]) returns setof h3indexDistance

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]) returns 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]) returns setof h3indexDistance

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(ARRAY h3index[, k]) returns 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]) returns 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) returns int

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_h3_to_parent(h3index[, parentRes]) returns 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_h3_to_parent('880326b88dfffff', 5);

h3_h3_to_parent

850326bbfffffff (1 row) ```

h3_h3_to_children(h3index[, childRes]) returns 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_h3_to_children_slow.

``` SELECT h3_h3_to_children('880326b88dfffff', 9);

h3_h3_to_children

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

h3_h3_to_children_slow(h3index[, childRes]) returns setof h3index

This functions does the same as h3_h3_to_children_slow but allocates smaller chunks of memory at the cost speed.

h3_compact(h3index[]) returns 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_h3_to_children('880326b88dfffff')), ARRAY(SELECT h3_h3_to_children('880326b88bfffff'))));

h3_compact

880326b88bfffff 880326b88dfffff (2 rows) ```

h3_uncompact(ARRAY h3index[, resolution]) returns 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_h3_to_parent('880326b88dfffff')), '{880326b88bfffff}'::h3index[]));

h3_uncompact

890326b8803ffff 890326b8807ffff 890326b880bffff 890326b880fffff 890326b8813ffff 890326b8817ffff 890326b881bffff 890326b8823ffff 890326b8827ffff 890326b882bffff 890326b882fffff 890326b8833ffff 890326b8837ffff 890326b883bffff 890326b8843ffff 890326b8847ffff 890326b884bffff 890326b884fffff 890326b8853ffff 890326b8857ffff 890326b885bffff 890326b8863ffff 890326b8867ffff 890326b886bffff 890326b886fffff 890326b8873ffff 890326b8877ffff 890326b887bffff 890326b8883ffff 890326b8887ffff 890326b888bffff 890326b888fffff 890326b8893ffff 890326b8897ffff 890326b889bffff 890326b88a3ffff 890326b88a7ffff 890326b88abffff 890326b88afffff 890326b88b3ffff 890326b88b7ffff 890326b88bbffff 890326b88c3ffff 890326b88c7ffff 890326b88cbffff 890326b88cfffff 890326b88d3ffff 890326b88d7ffff 890326b88dbffff 890326b88a3ffff 890326b88a7ffff 890326b88abffff 890326b88afffff 890326b88b3ffff 890326b88b7ffff 890326b88bbffff (56 rows) ```

Region functions

h3_polyfill(exterior polygon, holes polygon[], resolution integer) returns 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_h3_set_to_linked_geo(ARRAY(SELECT h3_h3_to_children('8059fffffffffff, 1))) ) q;

h3_polyfill

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

h3_h3_set_to_linked_geo(h3index[]) returns SET (exterior polygon, holes polygon[])

Create records of exteriors and holes.

``` SELECT h3_polyfill(exterior, holes, 1) FROM ( SELECT * FROM h3_h3_set_to_linked_geo(ARRAY(SELECT h3_h3_to_children('8059fffffffffff, 1))) ) q;

h3_polyfill

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

Unidirectional Edges

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

h3_h3_indexes_are_neighbors(h3index, h3index) returns boolean

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

SELECT h3_h3_indexes_are_neighbors(:hexagon, '880326b8ebfffff'), h3_h3_indexes_are_neighbors('880326b881fffff', '880326b8ebfffff'); h3_h3_indexes_are_neighbors | h3_h3_indexes_are_neighbors --------------------------+-------------------------- t | f (1 row)

h3_get_h3_unidirectional_edge(origin h3index, destination h3index) returns 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_h3_unidirectional_edge_is_valid(h3index) returns boolean

Returns true if the given hex is a valid edge.

``` SELECT h3_h3_unidirectional_edge_is_valid(h3_get_h3_unidirectional_edge(:hexagon, :neighbour));

h3_h3_unidirectional_edge_is_valid

t (1 row) ```

h3_get_origin_h3_index_from_unidirectional_edge(h3index) returns 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) returns 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) returns edgeIndexes (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) returns 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) returns polygon

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

``` SELECT h3_get_unidirectional_edge_boundary(h3_get_h3_unidirectional_edge(:hexagon, :neighbour));

h3_get_unidirectional_edge_boundary

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

Miscellaneous

h3_degs_to_rads(float) returns float

Converts degrees to radians.

``` SELECT h3_rads_to_degs(degs_to_rads(90.45));

h3_rads_to_degs

    90.45

(1 row) ```

h3_rads_to_degs(float) returns float

Converts radians to degrees.

``` SELECT h3_rads_to_degs(degs_to_rads(90.45));

h3_rads_to_degs

    90.45

(1 row) ```

h3_hex_area_km2(resolution integer) returns 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) retuns 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) returns 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) returns 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) returns bigint

Returns the number of unique indexes at the given resolution

``` SELECT h3_num_hexagons(15);

h3_num_hexagons

569707381193162 (1 row) ```

PostGIS integration

We provide some simple wrappers for casting to PostGIS types.

h3_geo_to_h3(geometry / geography, resolution)

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

h3_h3_to_geometry(h3index) returns geometry

Finds the centroid of this hex as PostGIS geometry type.

``` SELECT h3_h3_to_geometry('8a63a9a99047fff');

h3_h3_to_geometry

0101000020E61000008BE4AED877D54B40C46F27D42B2F2940 (1 row) ```

h3_h3_to_geography(h3index) returns geography

Same as above, but returns geography type.

h3_h3_to_geo_boundary_geometry(h3index) returns geometry

Find the boundary of this hex, as PostGIS type.

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

boundary_geometry

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

h3_h3_to_geo_boundary_geography(h3index) returns geography

Same as above, but returns geography type.

Custom functions

h3_basecells() returns setof h3index

Returns all hexes at coarsest resolution.

``` SELECT h3_basecells();

h3_basecells

8001fffffffffff ... 80f3fffffffffff (122 rows) ```

haversine_distance(from h3index, to h3index) returns float

Determines the distance between from_hex and to_hex, based on Haversine Distance.

``` SELECT h3_haversine_distance('8f2830828052d25', '8f283082a30e623');

h3_haversine_distance

2.25685336707384 (1 row) ```