ClickHouse/dbms/Common/WeakHash.h

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#pragma once
#include <Common/PODArray.h>
namespace DB
{
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/// It's a class which represents the result of weak and fast hash function per row in column.
/// It's usually hardware accelerated CRC32-C.
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/// Has function result may be combined to calculate hash for tuples.
///
/// The main purpose why this class needed is to support data initialization. Initially, every bit is 1.
class WeakHash32
{
public:
using Container = PaddedPODArray<UInt32>;
explicit WeakHash32(size_t size) : data(size, ~UInt32(0)) {}
WeakHash32(const WeakHash32 & other) { data.assign(other.data); }
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const Container & getData() const { return data; }
Container & getData() { return data; }
private:
PaddedPODArray<UInt32> data;
};
}