Yes, some basic functions already exist :)
After thinking about it some more, I'm wondering if it may be better to
implement something like:
- st_geohash_envelope_cover(envelope)->List<Geohash String>
- st_geohash_contained_geohashes_at_depth(Geohash, int precision) ->
list<Geohash str>
i believe for cover the algorithm i plan on implementing will essentially
be:
1. given an envelope
2. From envelope size, derive the correct geohash scale such that worse
case scenario each corner is in a distinct geohash.
3. return a list of the geohashes
the above is O(1).
if we then add functions to create containing geohashes (eg: for geohash DR
give all three digits contained by DR.. {DR1, DR2...} we can let users use
other functionality to do whatever they'd like. but at the same time, once
we implement the first few foundational functions the rest are much easier.
for example:
- Users may want to compact or not compact geohashes
- may wish to use INTERSECTS instead of COVERS, or any other predicate.
- may wish to increase or decrease resolution of the returned geohashes to
have a more or less accurate version
This is also somewhat easy to do, but I'm not a java developer so it may
take me awhile. If you or anyone else has any thoughts of what actual
functions should be implemented I'd also be happy to hear them :)
On Wed, Feb 15, 2023, 10:54 PM Jia Yu <[email protected]> wrote:
> BTW, the basic GeoHash function is already in Sedona. I believe this
> function just need to extend those basic GeoHash funcs.
>
> On Wed, Feb 15, 2023 at 5:59 PM Jia Yu <[email protected]> wrote:
>
>>
>>
>> On Wed, Feb 15, 2023 at 5:59 PM Jia Yu <[email protected]> wrote:
>>
>>> This is a fantastic idea. Would you please add it to Sedona? This will
>>> definitely benefit many Sedona users!
>>>
>>> Jia
>>>
>>> On Wed, Feb 15, 2023 at 9:49 AM Zachary Paden <[email protected]>
>>> wrote:
>>>
>>>> Hello all,
>>>>
>>>> As a sedona user, I'd like to be able to create covers and compress
>>>> geohashes. These are features of some IBM libraries
>>>> <
>>>> https://www.ibm.com/docs/ja/db2-warehouse?topic=concepts-geohashes-geohash-covers
>>>> >.
>>>>
>>>>
>>>> Essentially I'd like to add something akin to `ST_GEOHASH_COVER`
>>>> function
>>>> and perhaps a `ST_GEOHASH_COMPRESSION` function. This surprisingly
>>>> doesn't
>>>> have much support in OSS libraries as far as I can tell, but
>>>> implementation
>>>> on some level should be doable IMO.
>>>>
>>>> This would allow users to use geohash as another way to index their
>>>> data,
>>>> one that is more compatible with other query engines (EG: Anything that
>>>> supports can support geohashes on some level)
>>>>
>>>
