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92 lines
2.8 KiB
C++
92 lines
2.8 KiB
C++
#include <Functions/FunctionFactory.h>
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#include <DataTypes/DataTypeString.h>
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#include <Columns/ColumnString.h>
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#include <Common/typeid_cast.h>
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#include <Common/memcpySmall.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int ILLEGAL_COLUMN;
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extern const int ILLEGAL_TYPE_OF_ARGUMENT;
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}
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/** Function for transforming numbers and dates to strings that contain the same set of bytes in the machine representation. */
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class FunctionReinterpretAsString : public IFunction
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{
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public:
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static FunctionPtr create(const Context &) { return std::make_shared<FunctionReinterpretAsString>(); }
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static constexpr auto name = "reinterpretAsString";
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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 { return 1; }
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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{
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const IDataType & type = *arguments[0];
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if (type.isValueUnambiguouslyRepresentedInContiguousMemoryRegion())
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return std::make_shared<DataTypeString>();
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throw Exception("Cannot reinterpret " + type.getName() + " as String because it is not contiguous in memory", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
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}
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static void executeToString(const IColumn & src, ColumnString & dst)
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{
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size_t rows = src.size();
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ColumnString::Chars & data_to = dst.getChars();
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ColumnString::Offsets & offsets_to = dst.getOffsets();
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offsets_to.resize(rows);
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ColumnString::Offset offset = 0;
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for (size_t i = 0; i < rows; ++i)
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{
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StringRef data = src.getDataAt(i);
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/// Cut trailing zero bytes.
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while (data.size && data.data[data.size - 1] == 0)
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--data.size;
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data_to.resize(offset + data.size + 1);
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memcpySmallAllowReadWriteOverflow15(&data_to[offset], data.data, data.size);
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offset += data.size;
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data_to[offset] = 0;
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++offset;
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offsets_to[i] = offset;
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}
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}
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bool useDefaultImplementationForConstants() const override { return true; }
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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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const IColumn & src = *block.getByPosition(arguments[0]).column;
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MutableColumnPtr dst = block.getByPosition(result).type->createColumn();
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if (ColumnString * dst_concrete = typeid_cast<ColumnString *>(dst.get()))
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executeToString(src, *dst_concrete);
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else
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throw Exception("Illegal column " + src.getName() + " of argument of function " + getName(), ErrorCodes::ILLEGAL_COLUMN);
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block.getByPosition(result).column = std::move(dst);
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}
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};
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void registerFunctionReinterpretAsString(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionReinterpretAsString>();
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}
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}
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