1 | #pragma once |
2 | |
3 | #include <Core/Block.h> |
4 | #include <Core/Field.h> |
5 | #include <Parsers/IAST.h> |
6 | #include <Parsers/IParser.h> |
7 | |
8 | #include <memory> |
9 | #include <optional> |
10 | |
11 | |
12 | namespace DB |
13 | { |
14 | |
15 | class Context; |
16 | class ExpressionActions; |
17 | class IDataType; |
18 | |
19 | using ExpressionActionsPtr = std::shared_ptr<ExpressionActions>; |
20 | |
21 | /** Evaluate constant expression and its type. |
22 | * Used in rare cases - for elements of set for IN, for data to INSERT. |
23 | * Throws exception if it's not a constant expression. |
24 | * Quite suboptimal. |
25 | */ |
26 | std::pair<Field, std::shared_ptr<const IDataType>> evaluateConstantExpression(const ASTPtr & node, const Context & context); |
27 | |
28 | |
29 | /** Evaluate constant expression and returns ASTLiteral with its value. |
30 | */ |
31 | ASTPtr evaluateConstantExpressionAsLiteral(const ASTPtr & node, const Context & context); |
32 | |
33 | |
34 | /** Evaluate constant expression and returns ASTLiteral with its value. |
35 | * Also, if AST is identifier, then return string literal with its name. |
36 | * Useful in places where some name may be specified as identifier, or as result of a constant expression. |
37 | */ |
38 | ASTPtr evaluateConstantExpressionOrIdentifierAsLiteral(const ASTPtr & node, const Context & context); |
39 | |
40 | /** Try to fold condition to countable set of constant values. |
41 | * @param condition a condition that we try to fold. |
42 | * @param target_expr expression evaluated over a set of constants. |
43 | * @return optional blocks each with a single row and a single column for target expression, |
44 | * or empty blocks if condition is always false, |
45 | * or nothing if condition can't be folded to a set of constants. |
46 | */ |
47 | std::optional<Blocks> evaluateExpressionOverConstantCondition(const ASTPtr & condition, const ExpressionActionsPtr & target_expr); |
48 | |
49 | } |
50 | |