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METR-22322: rename function, add comments

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This commit is contained in:
serebrserg 2016-08-14 15:18:11 +03:00
parent 429b73422f
commit db5bae495b
2 changed files with 38 additions and 26 deletions
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62
dbms/include/DB/Functions/FunctionsGeo.h
View File

@ -5,21 +5,28 @@
#include <ext/range.hpp>
#include <math.h>
#define D_R (M_PI / 180.0)
#define DEGREES_IN_RADIANS (M_PI / 180.0)
namespace DB{
const Float64 EARTH_RADIUS_IN_METERS = 6372797.560856;
static inline Float64 deg_rad(Float64 ang) { return ang * D_R; }
static inline Float64 rad_deg(Float64 ang) { return ang / D_R; }
static inline Float64 degToRad(Float64 angle) { return angle * DEGREES_IN_RADIANS; }
static inline Float64 radToDeg(Float64 angle) { return angle / DEGREES_IN_RADIANS; }
class FunctionGeoDistance : public IFunction
/**
* The function calculates distance in meters between two points on Earth specified by longitude and latitude in degrees.
* The function uses great circle distance formula https://en.wikipedia.org/wiki/Great-circle_distance.
* Throws exception when one or several input values are not within reasonable bounds.
* Latitude must be in [-90, 90], longitude must be [-180, 180]
*
*/
class FunctionGreatCircleDistance : public IFunction
{
public:
static constexpr auto name = "distance";
static FunctionPtr create(const Context &) { return std::make_shared<FunctionGeoDistance>(); }
static constexpr auto name = "greatCircleDistance";
static FunctionPtr create(const Context &) { return std::make_shared<FunctionGreatCircleDistance>(); }
private:
@ -47,7 +54,7 @@ private:
const auto arg = arguments[arg_idx].get();
if (!typeid_cast<const DataTypeFloat64 *>(arg))
throw Exception(
"Illegal type " + arg->getName() + " of argument " + std::to_string(arg_idx + 1) + " of function " + getName(),
"Illegal type " + arg->getName() + " of argument " + std::to_string(arg_idx + 1) + " of function " + getName() + ". Must be Float64",
ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
}
@ -57,8 +64,7 @@ private:
instrs_t getInstructions(const Block & block, const ColumnNumbers & arguments, bool & out_const)
{
instrs_t result{};
result.reserve(arguments.size());
out_const = true;
for (const auto arg_pos : arguments)
@ -68,13 +74,10 @@ private:
if (const auto col = typeid_cast<const ColumnVector<Float64> *>(column))
{
out_const = false;
result.emplace_back(instr_type::get_float_64, col);
}
else if (const auto col = typeid_cast<const ColumnConst<Float64> *>(column))
{
out_const = out_const && true;
result.emplace_back(instr_type::get_const_float_64, col);
}
else
@ -85,17 +88,24 @@ private:
return result;
}
Float64 geohashGetDistance(Float64 lon1d, Float64 lat1d, Float64 lon2d, Float64 lat2d) {
Float64 lat1r, lon1r, lat2r, lon2r, u, v;
lat1r = deg_rad(lat1d);
lon1r = deg_rad(lon1d);
lat2r = deg_rad(lat2d);
lon2r = deg_rad(lon2d);
u = sin((lat2r - lat1r) / 2);
v = sin((lon2r - lon1r) / 2);
return 2.0 * EARTH_RADIUS_IN_METERS *
asin(sqrt(u * u + cos(lat1r) * cos(lat2r) * v * v));
/// https://en.wikipedia.org/wiki/Great-circle_distance
Float64 greatCircleDistance(Float64 lon1Deg, Float64 lat1Deg, Float64 lon2Deg, Float64 lat2Deg) {
if (lon1Deg < -180 || lon1Deg > 180 ||
lon2Deg < -180 || lon2Deg > 180 ||
lat1Deg < -90 || lat1Deg > 90 ||
lat2Deg < -90 || lat2Deg > 90
)
{
throw Exception("Illegal values of columns. Must be within bounds.");
}
Float64 lon1Rad = degToRad(lon1Deg);
Float64 lat1Rad = degToRad(lat1Deg);
Float64 lon2Rad = degToRad(lon2Deg);
Float64 lat2Rad = degToRad(lat2Deg);
Float64 u = sin((lat2Rad - lat1Rad) / 2);
Float64 v = sin((lon2Rad - lon1Rad) / 2);
return 2.0 * EARTH_RADIUS_IN_METERS * asin(sqrt(u * u + cos(lat1Rad) * cos(lat2Rad) * v * v));
}
@ -113,7 +123,7 @@ private:
const auto & colLon2 = static_cast<const ColumnConst<Float64> *>(block.getByPosition(arguments[2]).column.get())->getData();
const auto & colLat2 = static_cast<const ColumnConst<Float64> *>(block.getByPosition(arguments[3]).column.get())->getData();
Float64 res = geohashGetDistance(colLon1, colLat1, colLon2, colLat2);
Float64 res = greatCircleDistance(colLon1, colLat1, colLon2, colLat2);
block.getByPosition(result).column = std::make_shared<ColumnConst<Float64>>(size, res);
}
else
@ -134,9 +144,11 @@ private:
else
throw std::logic_error{"unknown instr_type"};
}
dst_data[row] = geohashGetDistance(vals[0], vals[1], vals[2], vals[3]);
dst_data[row] = greatCircleDistance(vals[0], vals[1], vals[2], vals[3]);
}
}
}
};
}
#undef DEGREES_IN_RADIANS

2
dbms/src/Functions/FunctionsGeo.cpp
View File

@ -7,6 +7,6 @@ namespace DB
void registerFunctionsGeo(FunctionFactory & factory)
{
factory.registerFunction<FunctionGeoDistance>();
factory.registerFunction<FunctionGreatCircleDistance>();
}
}