From a6806043352f1662c30d736f61eae3491e93f3cb Mon Sep 17 00:00:00 2001
From: bharatnc <bharatnc@gmail.com>
Date: Fri, 14 Jan 2022 00:02:41 -0800
Subject: [PATCH] add h3NumHexagons func

---
 src/Functions/h3NumHexagons.cpp        | 90 ++++++++++++++++++++++++++
 src/Functions/registerFunctionsGeo.cpp |  2 +
 2 files changed, 92 insertions(+)
 create mode 100644 src/Functions/h3NumHexagons.cpp

diff --git a/src/Functions/h3NumHexagons.cpp b/src/Functions/h3NumHexagons.cpp
new file mode 100644
index 00000000000..643b62730d4
--- /dev/null
+++ b/src/Functions/h3NumHexagons.cpp
@@ -0,0 +1,90 @@
+#include "config_functions.h"
+
+#if USE_H3
+
+#include <Columns/ColumnsNumber.h>
+#include <DataTypes/DataTypesNumber.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/IFunction.h>
+#include <IO/WriteHelpers.h>
+#include <Common/typeid_cast.h>
+#include <base/range.h>
+
+#include <constants.h>
+#include <h3api.h>
+
+
+namespace DB
+{
+namespace ErrorCodes
+{
+extern const int ILLEGAL_TYPE_OF_ARGUMENT;
+extern const int ILLEGAL_COLUMN;
+}
+
+namespace
+{
+
+class FunctionH3NumHexagons : public IFunction
+{
+public:
+    static constexpr auto name = "h3NumHexagons";
+
+    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionH3NumHexagons>(); }
+
+    std::string getName() const override { return name; }
+
+    size_t getNumberOfArguments() const override { return 1; }
+    bool useDefaultImplementationForConstants() const override { return true; }
+    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
+
+    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
+    {
+        const auto * arg = arguments[0].get();
+        if (!WhichDataType(arg).isUInt8())
+            throw Exception(
+                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
+                "Illegal type {} of argument {} of function {}. Must be UInt8",
+                arg->getName(), 1, getName());
+
+        return std::make_shared<DataTypeFloat64>();
+    }
+
+    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override
+    {
+        const auto * column = checkAndGetColumn<ColumnUInt8>(arguments[0].column.get());
+        if (!column)
+            throw Exception(
+                ErrorCodes::ILLEGAL_COLUMN,
+                "Illegal type {} of argument {} of function {}. Must be UInt8",
+                arguments[0].type->getName(),
+                1,
+                getName());
+
+        const auto & data = column->getData();
+
+        auto dst = ColumnVector<Float64>::create();
+        auto & dst_data = dst->getData();
+        dst_data.resize(input_rows_count);
+
+        for (size_t row = 0; row < input_rows_count; ++row)
+        {
+            const UInt64 resolution = data[row];
+            Float64 res = getNumCells(resolution);
+            dst_data[row] = res;
+        }
+
+        return dst;
+    }
+};
+
+}
+
+void registerFunctionH3NumHexagons(FunctionFactory & factory)
+{
+    factory.registerFunction<FunctionH3NumHexagons>();
+}
+
+}
+
+#endif
diff --git a/src/Functions/registerFunctionsGeo.cpp b/src/Functions/registerFunctionsGeo.cpp
index ee407926ffa..74fb429e03b 100644
--- a/src/Functions/registerFunctionsGeo.cpp
+++ b/src/Functions/registerFunctionsGeo.cpp
@@ -52,6 +52,7 @@ void registerFunctionH3RadsToDegs(FunctionFactory &);
 void registerFunctionH3HexAreaKm2(FunctionFactory &);
 void registerFunctionH3CellAreaM2(FunctionFactory &);
 void registerFunctionH3CellAreaRads2(FunctionFactory &);
+void registerFunctionH3NumHexagons(FunctionFactory &);
 
 #endif
 
@@ -118,6 +119,7 @@ void registerFunctionsGeo(FunctionFactory & factory)
     registerFunctionH3HexAreaKm2(factory);
     registerFunctionH3CellAreaM2(factory);
     registerFunctionH3CellAreaRads2(factory);
+    registerFunctionH3NumHexagons(factory);
 #endif
 
 #if USE_S2_GEOMETRY