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Slightly optimize ColumnArray::get()/operator[] (by using reserve over resize)

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Note, that simple "SELECT range(100)" will execute
ColumnArray::operator[] 14 times (most of them from
DB::checkColumnStructure())

Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
This commit is contained in:
Azat Khuzhin 2022-01-27 13:54:38 +03:00
parent 63d8d75001
commit 4e07122079
1 changed files with 6 additions and 4 deletions
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10
src/Columns/ColumnArray.cpp
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@ -134,10 +134,11 @@ Field ColumnArray::operator[](size_t n) const
throw Exception(ErrorCodes::TOO_LARGE_ARRAY_SIZE, "Array of size {} is too large to be manipulated as single field, maximum size {}",
size, max_array_size_as_field);
Array res(size);
Array res;
res.reserve(size);
for (size_t i = 0; i < size; ++i)
res[i] = getData()[offset + i];
res.push_back(getData()[offset + i]);
return res;
}
@ -152,11 +153,12 @@ void ColumnArray::get(size_t n, Field & res) const
throw Exception(ErrorCodes::TOO_LARGE_ARRAY_SIZE, "Array of size {} is too large to be manipulated as single field, maximum size {}",
size, max_array_size_as_field);
res = Array(size);
res = Array();
Array & res_arr = DB::get<Array &>(res);
res_arr.reserve(size);
for (size_t i = 0; i < size; ++i)
getData().get(offset + i, res_arr[i]);
res_arr.push_back(getData()[offset + i]);
}