ClickHouse

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#include <Functions/IFunction.h>
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#include <Functions/FunctionFactory.h>
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#include <DataTypes/DataTypeString.h>
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#include <Core/Field.h>
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namespace DB
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{
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namespace
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{
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/// Dump the structure of type and column.
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class FunctionDumpColumnStructure : public IFunction
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{
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public:
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    static constexpr auto name = "dumpColumnStructure";
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    static FunctionPtr create(ContextPtr)
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    {
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        return std::make_shared<FunctionDumpColumnStructure>();
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    }
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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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    bool useDefaultImplementationForNulls() const override { return false; }
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    bool useDefaultImplementationForNothing() const override { return false; }
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    bool useDefaultImplementationForLowCardinalityColumns() const override { return false; }
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    bool useDefaultImplementationForSparseColumns() const override { return false; }
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    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }
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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<DataTypeString>();
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    }
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    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override
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    {
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        const auto & elem = arguments[0];
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        /// Note that the result is not a constant, because it contains columns size.
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        return DataTypeString().createColumnConst(input_rows_count,
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                elem.type->getName() + ", " + elem.column->dumpStructure())->convertToFullColumnIfConst();
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    }
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};
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}
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REGISTER_FUNCTION(DumpColumnStructure)
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{
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    factory.registerFunction<FunctionDumpColumnStructure>();
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}
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}
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