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85 lines
2.5 KiB
C++
85 lines
2.5 KiB
C++
#include <Functions/IFunctionImpl.h>
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#include <Functions/FunctionFactory.h>
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#include <Functions/FunctionHelpers.h>
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#include <DataTypes/DataTypeString.h>
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#include <Columns/ColumnString.h>
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#include <Interpreters/Context.h>
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#include <Common/Macros.h>
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#include <Core/Field.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_TYPE_OF_ARGUMENT;
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extern const int ILLEGAL_COLUMN;
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}
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/** Get the value of macro from configuration file.
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* For example, it may be used as a sophisticated replacement for the function 'hostName' if servers have complicated hostnames
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* but you still need to distinguish them by some convenient names.
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*/
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class FunctionGetMacro : public IFunction
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{
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private:
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MultiVersion<Macros>::Version macros;
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public:
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static constexpr auto name = "getMacro";
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static FunctionPtr create(const Context & context)
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{
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return std::make_shared<FunctionGetMacro>(context.getMacros());
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}
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explicit FunctionGetMacro(MultiVersion<Macros>::Version macros_) : macros(std::move(macros_)) {}
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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 1;
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}
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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{
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if (!isString(arguments[0]))
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throw Exception("The argument of function " + getName() + " must have String type", ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
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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 & arguments, size_t result, size_t input_rows_count) override
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{
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const IColumn * arg_column = block.getByPosition(arguments[0]).column.get();
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const ColumnString * arg_string = checkAndGetColumnConstData<ColumnString>(arg_column);
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if (!arg_string)
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throw Exception("The argument of function " + getName() + " must be constant String", ErrorCodes::ILLEGAL_COLUMN);
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block.getByPosition(result).column = block.getByPosition(result).type->createColumnConst(
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input_rows_count, macros->getValue(arg_string->getDataAt(0).toString()))->convertToFullColumnIfConst();
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}
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};
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void registerFunctionGetMacro(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionGetMacro>();
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}
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}
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