From 590627a6582a02c6db15e9df1ad766e6bb0638be Mon Sep 17 00:00:00 2001
From: Konstantin Malanchev <hombit@gmail.com>
Date: Thu, 5 Dec 2019 16:22:10 +0300
Subject: [PATCH] Add h3EdgeAngle function

---
 dbms/src/Functions/h3EdgeAngle.cpp            | 78 +++++++++++++++++++
 dbms/src/Functions/registerFunctionsGeo.cpp   |  2 +
 .../0_stateless/01044_h3_edge_angle.reference |  2 +
 .../0_stateless/01044_h3_edge_angle.sql       |  2 +
 4 files changed, 84 insertions(+)
 create mode 100644 dbms/src/Functions/h3EdgeAngle.cpp
 create mode 100644 dbms/tests/queries/0_stateless/01044_h3_edge_angle.reference
 create mode 100644 dbms/tests/queries/0_stateless/01044_h3_edge_angle.sql

diff --git a/dbms/src/Functions/h3EdgeAngle.cpp b/dbms/src/Functions/h3EdgeAngle.cpp
new file mode 100644
index 00000000000..be3dac0e9d7
--- /dev/null
+++ b/dbms/src/Functions/h3EdgeAngle.cpp
@@ -0,0 +1,78 @@
+#include "config_functions.h"
+#if USE_H3
+#    include <Columns/ColumnsNumber.h>
+#    include <DataTypes/DataTypesNumber.h>
+#    include <Functions/FunctionFactory.h>
+#    include <Functions/IFunction.h>
+#    include <Common/typeid_cast.h>
+#    include <ext/range.h>
+
+
+extern "C" {
+#    ifdef __clang__
+#        pragma clang diagnostic push
+#        pragma clang diagnostic ignored "-Wdocumentation"
+#    endif
+
+#    include <h3api.h>
+
+#    ifdef __clang__
+#        pragma clang diagnostic pop
+#    endif
+}
+
+namespace DB
+{
+class FunctionH3EdgeAngle : public IFunction
+{
+public:
+    static constexpr auto name = "h3EdgeAngle";
+
+    static FunctionPtr create(const Context &) { return std::make_shared<FunctionH3EdgeAngle>(); }
+
+    std::string getName() const override { return name; }
+
+    size_t getNumberOfArguments() const override { return 1; }
+    bool useDefaultImplementationForConstants() const override { return true; }
+
+    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
+    {
+        auto arg = arguments[0].get();
+        if (!WhichDataType(arg).isUInt8())
+            throw Exception(
+                "Illegal type " + arg->getName() + " of argument " + std::to_string(1) + " of function " + getName() + ". Must be UInt8",
+                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
+
+        return std::make_shared<DataTypeFloat64>();
+    }
+
+    void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
+    {
+        const auto col_hindex = block.getByPosition(arguments[0]).column.get();
+
+        auto dst = ColumnVector<Float64>::create();
+        auto & dst_data = dst->getData();
+        dst_data.resize(input_rows_count);
+
+        for (const auto row : ext::range(0, input_rows_count))
+        {
+            const int resolution = col_hindex->getUInt(row);
+
+            // Numerical constant is 180 degrees / pi / Earth radius, Earth radius is from h3 sources
+            Float64 res = 8.99320592271288084e-6 * H3_EXPORT(edgeLengthM)(resolution);
+
+            dst_data[row] = res;
+        }
+
+        block.getByPosition(result).column = std::move(dst);
+    }
+};
+
+
+void registerFunctionH3EdgeAngle(FunctionFactory & factory)
+{
+    factory.registerFunction<FunctionH3EdgeAngle>();
+}
+
+}
+#endif
diff --git a/dbms/src/Functions/registerFunctionsGeo.cpp b/dbms/src/Functions/registerFunctionsGeo.cpp
index 0a102dbbecc..b3e164145a8 100644
--- a/dbms/src/Functions/registerFunctionsGeo.cpp
+++ b/dbms/src/Functions/registerFunctionsGeo.cpp
@@ -14,6 +14,7 @@ void registerFunctionGeohashesInBox(FunctionFactory & factory);
 
 #if USE_H3
 void registerFunctionGeoToH3(FunctionFactory &);
+void registerFunctionH3EdgeAngle(FunctionFactory &);
 void registerFunctionH3EdgeLengthM(FunctionFactory &);
 void registerFunctionH3GetResolution(FunctionFactory &);
 void registerFunctionH3IsValid(FunctionFactory &);
@@ -31,6 +32,7 @@ void registerFunctionsGeo(FunctionFactory & factory)
 
 #if USE_H3
     registerFunctionGeoToH3(factory);
+	registerFunctionH3EdgeAngle(factory);
 	registerFunctionH3EdgeLengthM(factory);
 	registerFunctionH3GetResolution(factory);
 	registerFunctionH3IsValid(factory);
diff --git a/dbms/tests/queries/0_stateless/01044_h3_edge_angle.reference b/dbms/tests/queries/0_stateless/01044_h3_edge_angle.reference
new file mode 100644
index 00000000000..e64c5a2787e
--- /dev/null
+++ b/dbms/tests/queries/0_stateless/01044_h3_edge_angle.reference
@@ -0,0 +1,2 @@
+0.0005927224846720883
+0
diff --git a/dbms/tests/queries/0_stateless/01044_h3_edge_angle.sql b/dbms/tests/queries/0_stateless/01044_h3_edge_angle.sql
new file mode 100644
index 00000000000..a22121971f4
--- /dev/null
+++ b/dbms/tests/queries/0_stateless/01044_h3_edge_angle.sql
@@ -0,0 +1,2 @@
+SELECT h3EdgeAngle(10);
+SELECT h3EdgeLengthM(2) * 180 / pi() / 6371007.180918475 - h3EdgeAngle(2);