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
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
|
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SQL_META_TABLE_H_
#define SQL_META_TABLE_H_
#include <cstdint>
#include <string>
#include "base/component_export.h"
#include "base/memory/raw_ptr.h"
#include "base/strings/string_piece_forward.h"
namespace sql {
class Database;
// Creates and manages a table to store generic metadata. The features provided
// are:
// * An interface for storing multi-typed key-value data.
// * Helper methods to assist in database schema version control.
// * Historical data on past attempts to mmap the database to make it possible
// to avoid unconditionally retrying to load broken databases.
class COMPONENT_EXPORT(SQL) MetaTable {
public:
MetaTable();
MetaTable(const MetaTable&) = delete;
MetaTable& operator=(const MetaTable&) = delete;
~MetaTable();
// Values for Get/SetMmapStatus(). `kMmapFailure` indicates that there was at
// some point a read error and the database should not be memory-mapped, while
// `kMmapSuccess` indicates that the entire file was read at some point and
// can be memory-mapped without constraint.
static constexpr int64_t kMmapFailure = -2;
static constexpr int64_t kMmapSuccess = -1;
// Returns true if the 'meta' table exists.
static bool DoesTableExist(Database* db);
// Deletes the 'meta' table if it exists, returning false if an internal error
// occurred during the deletion and true otherwise (no matter whether the
// table existed).
static bool DeleteTableForTesting(Database* db);
// If the current version of the database is less than
// `lowest_supported_version`, or the current version is less than the
// database's least compatible version, razes the database. To only enforce
// the latter, pass `kNoLowestSupportedVersion` for
// `lowest_supported_version`.
//
// TODO(crbug.com/1228463): At this time the database is razed IFF meta exists
// and contains a version row with the value not satisfying the constraints.
// It may make sense to also raze if meta exists but has no version row, or if
// meta doesn't exist. In those cases if the database is not already empty, it
// probably resulted from a broken initialization.
// TODO(crbug.com/1228463): Folding this into Init() would allow enforcing
// the version constraint, but Init() is often called in a transaction.
static constexpr int kNoLowestSupportedVersion = 0;
static void RazeIfIncompatible(Database* db,
int lowest_supported_version,
int current_version);
// Used to tuck some data into the meta table about mmap status. The value
// represents how much data in bytes has successfully been read from the
// database, or `kMmapFailure` or `kMmapSuccess`.
static bool GetMmapStatus(Database* db, int64_t* status);
static bool SetMmapStatus(Database* db, int64_t status);
// Initializes the MetaTableHelper, providing the `Database` pointer and
// creating the meta table if necessary. Must be called before any other
// non-static methods. For new tables, it will initialize the version number
// to `version` and the compatible version number to `compatible_version`.
// Versions must be greater than 0 to distinguish missing versions (see
// GetVersionNumber()). If there was no meta table (proxy for a fresh
// database), mmap status is set to `kMmapSuccess`.
bool Init(Database* db, int version, int compatible_version);
// Resets this MetaTable object, making another call to Init() possible.
void Reset();
// The version number of the database. This should be the version number of
// the creator of the file. The version number will be 0 if there is no
// previously set version number.
//
// See also Get/SetCompatibleVersionNumber().
void SetVersionNumber(int version);
int GetVersionNumber();
// The compatible version number is the lowest current version embedded in
// Chrome code that can still use this database. This is usually the same as
// the current version. In some limited cases, such as adding a column without
// a NOT NULL constraint, the SQL queries embedded in older code can still
// execute successfully.
//
// For example, if an optional column is added to a table in version 3, the
// new code will set the version to 3, and the compatible version to 2, since
// the code expecting version 2 databases can still read and write the table.
//
// Rule of thumb: check the version number when you're upgrading, but check
// the compatible version number to see if you can use the file at all. If
// it's larger than you code is expecting, fail.
//
// The compatible version number will be 0 if there is no previously set
// compatible version number.
void SetCompatibleVersionNumber(int version);
int GetCompatibleVersionNumber();
// Set the given arbitrary key with the given data. Returns true on success.
bool SetValue(base::StringPiece key, const std::string& value);
bool SetValue(base::StringPiece key, int64_t value);
// Retrieves the value associated with the given key. This will use sqlite's
// type conversion rules. It will return true on success.
bool GetValue(base::StringPiece key, std::string* value);
bool GetValue(base::StringPiece key, int* value);
bool GetValue(base::StringPiece key, int64_t* value);
// Deletes the key from the table.
bool DeleteKey(base::StringPiece key);
private:
raw_ptr<Database> db_ = nullptr;
};
} // namespace sql
#endif // SQL_META_TABLE_H_
|
