1 | #pragma once |
2 | |
3 | #include <Columns/IColumn.h> |
4 | |
5 | |
6 | namespace DB |
7 | { |
8 | |
9 | /// Support methods for implementation of WHERE, PREWHERE and HAVING. |
10 | |
11 | |
12 | /// Analyze if the column for filter is constant thus filter is always false or always true. |
13 | struct ConstantFilterDescription |
14 | { |
15 | bool always_false = false; |
16 | bool always_true = false; |
17 | |
18 | ConstantFilterDescription() {} |
19 | explicit ConstantFilterDescription(const IColumn & column); |
20 | }; |
21 | |
22 | |
23 | /// Obtain a filter from non constant Column, that may have type: UInt8, Nullable(UInt8). |
24 | struct FilterDescription |
25 | { |
26 | const IColumn::Filter * data = nullptr; /// Pointer to filter when it is not always true or always false. |
27 | ColumnPtr data_holder; /// If new column was generated, it will be owned by holder. |
28 | |
29 | explicit FilterDescription(const IColumn & column); |
30 | }; |
31 | |
32 | |
33 | struct ColumnWithTypeAndName; |
34 | |
35 | /// Will throw an exception if column_elem is cannot be used as a filter column. |
36 | void checkColumnCanBeUsedAsFilter(const ColumnWithTypeAndName & column_elem); |
37 | |
38 | } |
39 | |