ClickHouse

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#include "GatherUtils.h"
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#include "Sinks.h"
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#include "Sources.h"
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#include <base/TypeLists.h>
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namespace DB::GatherUtils
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{
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/// Creates IArraySource from ColumnArray
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namespace
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{
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template <typename... Types>
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struct ArraySourceCreator;
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template <typename Type, typename... Types>
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struct ArraySourceCreator<Type, Types...>
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{
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    static std::unique_ptr<IArraySource> create(const ColumnArray & col, const NullMap * null_map, bool is_const, size_t total_rows)
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    {
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        using ColVecType = ColumnVectorOrDecimal<Type>;
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        if (typeid_cast<const ColVecType *>(&col.getData()))
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        {
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            if (null_map)
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            {
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                if (is_const)
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                    return std::make_unique<ConstSource<NullableArraySource<NumericArraySource<Type>>>>(col, *null_map, total_rows);
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                return std::make_unique<NullableArraySource<NumericArraySource<Type>>>(col, *null_map);
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            }
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            if (is_const)
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                return std::make_unique<ConstSource<NumericArraySource<Type>>>(col, total_rows);
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            return std::make_unique<NumericArraySource<Type>>(col);
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        }
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        return ArraySourceCreator<Types...>::create(col, null_map, is_const, total_rows);
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    }
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};
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template <>
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struct ArraySourceCreator<>
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{
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    static std::unique_ptr<IArraySource> create(const ColumnArray & col, const NullMap * null_map, bool is_const, size_t total_rows)
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    {
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        if (null_map)
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        {
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            if (is_const)
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                return std::make_unique<ConstSource<NullableArraySource<GenericArraySource>>>(col, *null_map, total_rows);
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            return std::make_unique<NullableArraySource<GenericArraySource>>(col, *null_map);
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        }
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        if (is_const)
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            return std::make_unique<ConstSource<GenericArraySource>>(col, total_rows);
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        return std::make_unique<GenericArraySource>(col);
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    }
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};
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}
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std::unique_ptr<IArraySource> createArraySource(const ColumnArray & col, bool is_const, size_t total_rows)
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{
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    using Creator = TypeListChangeRoot<ArraySourceCreator, TypeListNumberWithUUID>;
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    if (const auto * column_nullable = typeid_cast<const ColumnNullable *>(&col.getData()))
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    {
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        auto column = ColumnArray::create(column_nullable->getNestedColumnPtr(), col.getOffsetsPtr());
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        return Creator::create(*column, &column_nullable->getNullMapData(), is_const, total_rows);
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    }
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    return Creator::create(col, nullptr, is_const, total_rows);
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}
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}
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