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82 lines
2.4 KiB
C++
82 lines
2.4 KiB
C++
#include <Functions/IFunction.h>
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#include <Functions/FunctionFactory.h>
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#include <DataTypes/DataTypesNumber.h>
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#include <Formats/FormatSettings.h>
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#include <Columns/ColumnsNumber.h>
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#include <IO/WriteBufferFromString.h>
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#include <Common/UTF8Helpers.h>
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#include <Common/assert_cast.h>
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namespace DB
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{
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/** visibleWidth(x) - calculates the approximate width when outputting the value in a text form to the console.
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* In fact it calculate the number of Unicode code points.
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* It does not support zero width and full width characters, combining characters, etc.
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*/
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class FunctionVisibleWidth : public IFunction
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{
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public:
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static constexpr auto name = "visibleWidth";
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static FunctionPtr create(const Context &)
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{
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return std::make_shared<FunctionVisibleWidth>();
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}
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bool useDefaultImplementationForNulls() const override { return false; }
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ColumnNumbers getArgumentsThatDontImplyNullableReturnType(size_t /*number_of_arguments*/) const override { return {0}; }
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/// Get the name of the function.
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String getName() const override
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{
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return name;
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}
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size_t getNumberOfArguments() const override
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{
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return 1;
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}
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DataTypePtr getReturnTypeImpl(const DataTypes & /*arguments*/) const override
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{
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return std::make_shared<DataTypeUInt64>();
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}
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bool useDefaultImplementationForConstants() const override { return true; }
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/// Execute the function on the block.
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void executeImpl(Block & block, const ColumnNumbers & arguments, size_t result, size_t input_rows_count) override
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{
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auto & src = block.getByPosition(arguments[0]);
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size_t size = input_rows_count;
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auto res_col = ColumnUInt64::create(size);
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auto & res_data = assert_cast<ColumnUInt64 &>(*res_col).getData();
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/// For simplicity reasons, function is implemented by serializing into temporary buffer.
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String tmp;
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FormatSettings format_settings;
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for (size_t i = 0; i < size; ++i)
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{
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{
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WriteBufferFromString out(tmp);
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src.type->serializeAsText(*src.column, i, out, format_settings);
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}
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res_data[i] = UTF8::countCodePoints(reinterpret_cast<const UInt8 *>(tmp.data()), tmp.size());
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}
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block.getByPosition(result).column = std::move(res_col);
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}
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};
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void registerFunctionVisibleWidth(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionVisibleWidth>();
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}
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}
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