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80 lines
2.4 KiB
C++
80 lines
2.4 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/DataTypeAggregateFunction.h>
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#include <Columns/ColumnAggregateFunction.h>
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#include <Common/typeid_cast.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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namespace
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{
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/** finalizeAggregation(agg_state) - get the result from the aggregation state.
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* Takes state of aggregate function. Returns result of aggregation (finalized state).
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*/
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class FunctionFinalizeAggregation : public IFunction
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{
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public:
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static constexpr auto name = "finalizeAggregation";
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static FunctionPtr create(const Context &)
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{
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return std::make_shared<FunctionFinalizeAggregation>();
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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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size_t getNumberOfArguments() const override
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{
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return 1;
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}
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bool useDefaultImplementationForConstants() const override { return true; }
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DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
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{
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const DataTypeAggregateFunction * type = checkAndGetDataType<DataTypeAggregateFunction>(arguments[0].get());
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if (!type)
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{
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throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
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"Argument for function '{}' must have type AggregateFunction - state of aggregate function."
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" Got '{}' instead", getName(), arguments[0]->getName());
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}
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return type->getReturnType();
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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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auto column = arguments.at(0).column;
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if (!typeid_cast<const ColumnAggregateFunction *>(column.get()))
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throw Exception("Illegal column " + arguments.at(0).column->getName()
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+ " of first argument of function "
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+ getName(),
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ErrorCodes::ILLEGAL_COLUMN);
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/// Column is copied here, because there is no guarantee that we own it.
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auto mut_column = IColumn::mutate(std::move(column));
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return ColumnAggregateFunction::convertToValues(std::move(mut_column));
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}
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};
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}
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void registerFunctionFinalizeAggregation(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionFinalizeAggregation>();
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}
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}
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