ClickHouse

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#include <AggregateFunctions/AggregateFunctionFactory.h>
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#include <AggregateFunctions/AggregateFunctionCount.h>
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#include <AggregateFunctions/FactoryHelpers.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 NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
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}
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struct Settings;
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AggregateFunctionPtr AggregateFunctionCount::getOwnNullAdapter(
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    const AggregateFunctionPtr &, const DataTypes & types, const Array & params, const AggregateFunctionProperties & /*properties*/) const
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{
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    return std::make_shared<AggregateFunctionCountNotNullUnary>(types[0], params);
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}
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namespace
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{
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AggregateFunctionPtr createAggregateFunctionCount(const std::string & name, const DataTypes & argument_types, const Array & parameters, const Settings *)
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{
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    assertNoParameters(name, parameters);
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    if (argument_types.size() > 1)
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        throw Exception(ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH, "Aggregate function {} requires zero or one argument", name);
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    return std::make_shared<AggregateFunctionCount>(argument_types);
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}
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}
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void registerAggregateFunctionCount(AggregateFunctionFactory & factory)
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{
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    AggregateFunctionProperties properties = { .returns_default_when_only_null = true, .is_order_dependent = false };
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    factory.registerFunction("count", {createAggregateFunctionCount, properties}, AggregateFunctionFactory::CaseInsensitive);
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}
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}
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