h3 functions required for circle search

[hombit]

I hereby agree to the terms of the CLA available at: https://yandex.ru/legal/cla/?lang=ru

Changelog category (leave one):

• New Feature

Changelog entry (up to few sentences, required except for Non-significant/Documentation categories):

Support of several h3 function in addition to geoToH3:

• h3GetResolution
• h3EdgeAngle
• h3EdgeLength
• h3IsValid
• h3kRing

Examples:

CREATE TABLE places
(
    `place` String,
    `lon` Float64,
    `lat` Float64,
    `h3index7` UInt64
)
ENGINE = Memory();

INSERT INTO places VALUES\
    ('Yandex', 37.588144, 55.733842, geoToH3(37.588144, 55.733842, 7)) \
    ('Moscow University',  37.531014, 55.703050, geoToH3(37.531014, 55.703050, 7)) \
    ('Uber',-122.4201594, 37.7756894, geoToH3(-122.4201594, 37.7756894,  7));

SELECT * FROM places WHERE h3index7 = geoToH3(37.542779, 55.701009, 7);

┌─place─────────────┬───────lon─┬──────lat─┬───────────h3index7─┐
│ Moscow University │ 37.531014 │ 55.70305 │ 608296731968274431 │
└───────────────────┴───────────┴──────────┴────────────────────┘

SELECT *
FROM places
WHERE h3index7 IN
(
    WITH
        37.577298 AS lon_,
        55.710832 AS lat_
    SELECT arrayJoin(h3kRing(geoToH3(lon_, lat_, 7), 1))
);

┌─place─────────────┬───────lon─┬───────lat─┬───────────h3index7─┐
│ Yandex            │ 37.588144 │ 55.733842 │ 608296731481735167 │
│ Moscow University │ 37.531014 │  55.70305 │ 608296731968274431 │
└───────────────────┴───────────┴───────────┴────────────────────┘

WITH
    37.577298 AS lon_,
    55.710832 AS lat_,
    3000 AS radius
SELECT *
FROM places
WHERE (h3index7 IN
(
    WITH
        37.577298 AS lon_,
        55.710832 AS lat_,
        3000 AS radius
    SELECT arrayJoin(h3kRing(geoToH3(lon_, lat_, 7), toUInt8(radius / h3EdgeLengthM(7))))
)) AND (greatCircleDistance(lon, lat, lon_, lat_) < radius)

┌─place──┬───────lon─┬───────lat─┬───────────h3index7─┐
│ Yandex │ 37.588144 │ 55.733842 │ 608296731481735167 │
└────────┴───────────┴───────────┴────────────────────┘

Fix #8000

[alexey-milovidov]

Maybe mark the include directory as SYSTEM in CMakeLists will help.

[hombit]

I just copy-pasted it from geoToH3.cpp, can you explain how should I fix it?

[hombit]

I've rebased it on current master

[stavrolia]

What does it happen here?

[stavrolia]

Is it possible to do without ignoring this flag? Actually we already have had documentation comment....

[hombit]

Actually, I don't know what it is for, I just copy-pasted it from geoToH3.cpp I'll remove it

[stavrolia]

In this case probably we can't do without it

[alexey-milovidov]

0042c82
0bc1c6d

1. Why I have removed warning suppression of -Wdocumentation for clang?

Because h3 headers are included as system headers:
https://github.com/ClickHouse/ClickHouse/blob/master/contrib/h3-cmake/CMakeLists.txt#L25
Compiler will suppress all warnings from system headers in the same way as for headers from /usr/include.

Why it's ok to suppress all warnings from 3rd party library?
Because we compile our code with much more warnings as usual (-Weverything) and it's natural for 3rd party code to not pass this checks.

2. Why I have removed extern "C" around include?

Because h3 library already contains #ifdef __cplusplus ... extern "C".

3. Why I have removed the usage of H3_EXPORT macro?

It is needed only if the user decided to prefix all h3 functions. We didn't do that.

[stavrolia]

Why don't we want to prefix C function from h3?

[alexey-milovidov]

Why don't we want to prefix C function from h3?

We don't need that - there is no name collisions.