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113 lines
3.8 KiB
C++
113 lines
3.8 KiB
C++
#include <Functions/IFunction.h>
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#include <Functions/FunctionFactory.h>
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#include <Functions/FunctionHelpers.h>
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#include <Columns/ColumnAggregateFunction.h>
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#include <DataTypes/DataTypeAggregateFunction.h>
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#include <Common/AlignedBuffer.h>
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#include <Common/Arena.h>
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#include <ext/scope_guard.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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/** runningAccumulate(agg_state) - takes the states of the aggregate function and returns a column with values,
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* are the result of the accumulation of these states for a set of block lines, from the first to the current line.
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*
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* Quite unusual function.
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* Takes state of aggregate function (example runningAccumulate(uniqState(UserID))),
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* and for each row of block, return result of aggregate function on merge of states of all previous rows and current row.
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*
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* So, result of function depends on partition of data to blocks and on order of data in block.
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*/
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class FunctionRunningAccumulate : public IFunction
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{
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public:
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static constexpr auto name = "runningAccumulate";
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static FunctionPtr create(const Context &)
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{
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return std::make_shared<FunctionRunningAccumulate>();
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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 isStateful() const override
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{
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return true;
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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 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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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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throw Exception("Argument for function " + getName() + " must have type AggregateFunction - state of aggregate function.",
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ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);
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return type->getReturnType();
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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 ColumnAggregateFunction * column_with_states
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= typeid_cast<const ColumnAggregateFunction *>(&*block.getByPosition(arguments.at(0)).column);
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if (!column_with_states)
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throw Exception("Illegal column " + block.getByPosition(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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AggregateFunctionPtr aggregate_function_ptr = column_with_states->getAggregateFunction();
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const IAggregateFunction & agg_func = *aggregate_function_ptr;
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AlignedBuffer place(agg_func.sizeOfData(), agg_func.alignOfData());
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agg_func.create(place.data());
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SCOPE_EXIT(agg_func.destroy(place.data()));
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std::unique_ptr<Arena> arena = agg_func.allocatesMemoryInArena() ? std::make_unique<Arena>() : nullptr;
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auto result_column_ptr = agg_func.getReturnType()->createColumn();
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IColumn & result_column = *result_column_ptr;
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result_column.reserve(column_with_states->size());
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const auto & states = column_with_states->getData();
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for (const auto & state_to_add : states)
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{
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/// Will pass empty arena if agg_func does not allocate memory in arena
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agg_func.merge(place.data(), state_to_add, arena.get());
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agg_func.insertResultInto(place.data(), result_column);
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}
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block.getByPosition(result).column = std::move(result_column_ptr);
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}
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};
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void registerFunctionRunningAccumulate(FunctionFactory & factory)
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{
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factory.registerFunction<FunctionRunningAccumulate>();
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}
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}
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