1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
|
#pragma once
#include <Core/Block.h>
#include <Formats/FormatSettings.h>
#include <Parsers/TokenIterator.h>
#include <Parsers/IAST.h>
#include <Interpreters/Context_fwd.h>
namespace DB
{
struct LiteralInfo;
using LiteralsInfo = std::vector<LiteralInfo>;
struct SpecialParserType;
class ExpressionActions;
using ExpressionActionsPtr = std::shared_ptr<ExpressionActions>;
/// Deduces template of an expression by replacing literals with dummy columns.
/// It allows to parse and evaluate similar expressions without using heavy IParsers and ExpressionAnalyzer.
/// Using ConstantExpressionTemplate for one expression is slower then evaluateConstantExpression(...),
/// but it's significantly faster for batch of expressions
class ConstantExpressionTemplate : boost::noncopyable
{
struct TemplateStructure : boost::noncopyable
{
TemplateStructure(LiteralsInfo & replaced_literals, TokenIterator expression_begin, TokenIterator expression_end,
ASTPtr & expr, const IDataType & result_type, bool null_as_default_, ContextPtr context);
static void addNodesToCastResult(const IDataType & result_column_type, ASTPtr & expr, bool null_as_default);
static size_t getTemplateHash(const ASTPtr & expression, const LiteralsInfo & replaced_literals,
const DataTypePtr & result_column_type, bool null_as_default, const String & salt);
String dumpTemplate() const;
String result_column_name;
std::vector<String> tokens;
std::vector<size_t> token_after_literal_idx;
Block literals;
ExpressionActionsPtr actions_on_literals;
Serializations serializations;
std::vector<SpecialParserType> special_parser;
bool null_as_default;
};
public:
using TemplateStructurePtr = std::shared_ptr<const TemplateStructure>;
class Cache : boost::noncopyable
{
std::unordered_map<size_t, TemplateStructurePtr> cache;
const size_t max_size;
public:
explicit Cache(size_t max_size_ = 4096) : max_size(max_size_) {}
/// Deduce template of expression of type result_column_type and add it to cache (or use template from cache)
TemplateStructurePtr getFromCacheOrConstruct(const DataTypePtr & result_column_type,
bool null_as_default,
TokenIterator expression_begin,
TokenIterator expression_end,
const ASTPtr & expression_,
ContextPtr context,
bool * found_in_cache = nullptr,
const String & salt = {});
};
explicit ConstantExpressionTemplate(const TemplateStructurePtr & structure_)
: structure(structure_), columns(structure->literals.cloneEmptyColumns()) {}
/// Read expression from istr, assert it has the same structure and the same types of literals (template matches)
/// and parse literals into temporary columns
bool parseExpression(
ReadBuffer & istr, const TokenIterator & token_iterator, const FormatSettings & format_settings, const Settings & settings);
/// Evaluate batch of expressions were parsed using template.
/// If template was deduced with null_as_default == true, set bits in nulls for NULL values in column_idx, starting from offset.
ColumnPtr evaluateAll(BlockMissingValues & nulls, size_t column_idx, const DataTypePtr & expected_type, size_t offset = 0);
size_t rowsCount() const { return rows_count; }
private:
bool tryParseExpression(
ReadBuffer & istr,
const TokenIterator & token_iterator,
const FormatSettings & format_settings,
size_t & cur_column,
const Settings & settings);
bool parseLiteralAndAssertType(
ReadBuffer & istr, const TokenIterator & token_iterator, const IDataType * type, size_t column_idx, const Settings & settings);
private:
TemplateStructurePtr structure;
MutableColumns columns;
/// For expressions without literals (e.g. "now()")
size_t rows_count = 0;
};
}
|
