The GIS standard and all the major DBs implementing GIS related
functions take coordinates as x,y that is longitude,latitude.
It was a bad start for Redis to do things differently, so even if this
means that existing users of the Geo module will be required to change
their code, Redis now conforms to the standard.
Usually Redis is very backward compatible, but this is not an exception
to this rule, since this is the first Geo implementation entering the
official Redis source code. It is not wise to try to be backward
compatible with code forks... :-)
Close#2637.
The returned step was in some case not enough towards normal
coordinates (for example when our search position was was already near the
margin of the central area, and we had to match, using the east or west
neighbor, a very far point). Example:
geoadd points 67.575457940146066 -62.001317572780565 far
geoadd points 66.685439060295664 -58.925040587282297 center
georadius points 66.685439060295664 -58.925040587282297 200 km
In the above case the code failed to find a match (happens at smaller
latitudes too) even if far and center are at less than 200km.
Another fix introduced by this commit is a progressively larger area
towards the poles, since meridians are a lot less far away, so we need
to compensate for this.
The current implementation works comparably to the Tcl brute-force
stress tester implemented in the fuzzy test in the geo.tcl unit for
latitudes between -70 and 70, and is pretty accurate over +/-80 too,
with sporadic false negatives.
A more mathematically clean implementation is possible by computing the
meridian distance at the specified latitude and computing the step
according to it.
Current todo:
- replace functions in zset.{c,h} with a new unified Redis
zset access API.
Once we get the zset interface fixed, we can squash
relevant commits in this branch and have one nice commit
to merge into unstable.
This commit adds:
- Geo commands
- Tests; runnable with: ./runtest --single unit/geo
- Geo helpers in deps/geohash-int/
- src/geo.{c,h} and src/geojson.{c,h} implementing geo commands
- Updated build configurations to get everything working
- TEMPORARY: src/zset.{c,h} implementing zset score and zset
range reading without writing to client output buffers.
- Modified linkage of one t_zset.c function for use in zset.c
Conflicts:
src/Makefile
src/redis.c
