ClickHouse/dbms/Functions/EmptyImpl.h

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#pragma once
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#include <Common/memcmpSmall.h>
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#include <Columns/ColumnString.h>
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#include <Functions/FunctionFactory.h>
namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
}
template <bool negative = false>
struct EmptyImpl
{
/// If the function will return constant value for FixedString data type.
static constexpr auto is_fixed_to_constant = false;
static void vector(const ColumnString::Chars & /*data*/, const ColumnString::Offsets & offsets, PaddedPODArray<UInt8> & res)
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{
size_t size = offsets.size();
ColumnString::Offset prev_offset = 1;
for (size_t i = 0; i < size; ++i)
{
res[i] = negative ^ (offsets[i] == prev_offset);
prev_offset = offsets[i] + 1;
}
}
/// Only make sense if is_fixed_to_constant.
static void vectorFixedToConstant(const ColumnString::Chars & /*data*/, size_t /*n*/, UInt8 & /*res*/)
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{
throw Exception("Logical error: 'vectorFixedToConstant method' is called", ErrorCodes::LOGICAL_ERROR);
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}
static void vectorFixedToVector(const ColumnString::Chars & data, size_t n, PaddedPODArray<UInt8> & res)
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{
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size_t size = data.size() / n;
for (size_t i = 0; i < size; ++i)
res[i] = negative ^ memoryIsZeroSmallAllowOverflow15(data.data() + i * n, n);
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}
static void array(const ColumnString::Offsets & offsets, PaddedPODArray<UInt8> & res)
{
size_t size = offsets.size();
ColumnString::Offset prev_offset = 0;
for (size_t i = 0; i < size; ++i)
{
res[i] = negative ^ (offsets[i] == prev_offset);
prev_offset = offsets[i];
}
}
};
}