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59 lines
1.5 KiB
C++
59 lines
1.5 KiB
C++
#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 <Common/DNSResolver.h>
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namespace DB
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{
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/// Get the host name. Is is constant on single server, but is not constant in distributed queries.
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class FunctionHostName : public IFunction
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{
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public:
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static constexpr auto name = "hostName";
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static FunctionPtr create(const Context &)
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{
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return std::make_shared<FunctionHostName>();
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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 isDeterministic() const override { return false; }
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bool isDeterministicInScopeOfQuery() const override
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{
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return false;
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}
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size_t getNumberOfArguments() const override
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{
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return 0;
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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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/** convertToFullColumn needed because in distributed query processing,
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* each server returns its own value.
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*/
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void executeImpl(Block & block, const ColumnNumbers &, size_t result, size_t input_rows_count) override
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{
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block.getByPosition(result).column = block.getByPosition(result).type->createColumnConst(
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input_rows_count, DNSResolver::instance().getHostName())->convertToFullColumnIfConst();
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}
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};
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void registerFunctionHostName(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionHostName>();
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}
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}
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