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Add a comment of getOwnNullAdapter()

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philip.han 2020-03-31 06:52:16 +09:00
parent 210024cd3a
commit 4c8c2d2933
1 changed files with 6 additions and 0 deletions
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6
dbms/src/AggregateFunctions/IAggregateFunction.h
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@ -151,6 +151,12 @@ public:
virtual void addBatchArray(
size_t batch_size, AggregateDataPtr * places, size_t place_offset, const IColumn ** columns, const UInt64 * offsets, Arena * arena) const = 0;
/** By default all NULLs are skipped during aggregation.
* If it returns nullptr, the default one will be used.
* If an aggregate function wants to use something instead of the default one, it overrides this function and returns its own null adapter.
* nested_function is a smart pointer to this aggregate function itself.
* arguments and params are for nested_function.
*/
virtual AggregateFunctionPtr getOwnNullAdapter(const AggregateFunctionPtr & /*nested_function*/, const DataTypes & /*arguments*/, const Array & /*params*/) const
{
return nullptr;