1 | /** |
---|---|
2 | * This file implements template methods of IColumn that depend on other types |
3 | * we don't want to include. |
4 | * Currently, this is only the scatterImpl method that depends on PODArray |
5 | * implementation. |
6 | */ |
7 | |
8 | #pragma once |
9 | |
10 | #include <Columns/IColumn.h> |
11 | #include <Common/PODArray.h> |
12 | |
13 | namespace DB |
14 | { |
15 | |
16 | template <typename Derived> |
17 | std::vector<IColumn::MutablePtr> IColumn::scatterImpl(ColumnIndex num_columns, |
18 | const Selector & selector) const |
19 | { |
20 | size_t num_rows = size(); |
21 | |
22 | if (num_rows != selector.size()) |
23 | throw Exception( |
24 | "Size of selector: "+ std::to_string(selector.size()) + " doesn't match size of column: "+ std::to_string(num_rows), |
25 | ErrorCodes::SIZES_OF_COLUMNS_DOESNT_MATCH); |
26 | |
27 | std::vector<MutablePtr> columns(num_columns); |
28 | for (auto & column : columns) |
29 | column = cloneEmpty(); |
30 | |
31 | { |
32 | size_t reserve_size = num_rows * 1.1 / num_columns; /// 1.1 is just a guess. Better to use n-sigma rule. |
33 | |
34 | if (reserve_size > 1) |
35 | for (auto & column : columns) |
36 | column->reserve(reserve_size); |
37 | } |
38 | |
39 | for (size_t i = 0; i < num_rows; ++i) |
40 | static_cast<Derived &>(*columns[selector[i]]).insertFrom(*this, i); |
41 | |
42 | return columns; |
43 | } |
44 | |
45 | } |
46 |