1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #ifndef SQL_META_TABLE_H_
6 #define SQL_META_TABLE_H_
10 #include "base/basictypes.h"
11 #include "sql/sql_export.h"
18 class SQL_EXPORT MetaTable {
23 // Returns true if the 'meta' table exists.
24 static bool DoesTableExist(Connection* db);
26 // If the current version of the database is less than or equal to
27 // |deprecated_version|, raze the database. Must be called outside
29 // TODO(shess): At this time the database is razed IFF meta exists
30 // and contains a version row with value <= deprecated_version. It
31 // may make sense to also raze if meta exists but has no version
32 // row, or if meta doesn't exist. In those cases if the database is
33 // not already empty, it probably resulted from a broken
35 // TODO(shess): Folding this into Init() would allow enforcing
36 // |deprecated_version|<|version|. But Init() is often called in a
38 static void RazeIfDeprecated(Connection* db, int deprecated_version);
40 // Initializes the MetaTableHelper, creating the meta table if necessary. For
41 // new tables, it will initialize the version number to |version| and the
42 // compatible version number to |compatible_version|. Versions must be
43 // greater than 0 to distinguish missing versions (see GetVersionNumber()).
44 bool Init(Connection* db, int version, int compatible_version);
46 // Resets this MetaTable object, making another call to Init() possible.
49 // The version number of the database. This should be the version number of
50 // the creator of the file. The version number will be 0 if there is no
51 // previously set version number.
53 // See also Get/SetCompatibleVersionNumber().
54 void SetVersionNumber(int version);
55 int GetVersionNumber();
57 // The compatible version number is the lowest version of the code that this
58 // database can be read by. If there are minor changes or additions, old
59 // versions of the code can still work with the database without failing.
61 // For example, if an optional column is added to a table in version 3, the
62 // new code will set the version to 3, and the compatible version to 2, since
63 // the code expecting version 2 databases can still read and write the table.
65 // Rule of thumb: check the version number when you're upgrading, but check
66 // the compatible version number to see if you can read the file at all. If
67 // it's larger than you code is expecting, fail.
69 // The compatible version number will be 0 if there is no previously set
70 // compatible version number.
71 void SetCompatibleVersionNumber(int version);
72 int GetCompatibleVersionNumber();
74 // Set the given arbitrary key with the given data. Returns true on success.
75 bool SetValue(const char* key, const std::string& value);
76 bool SetValue(const char* key, int value);
77 bool SetValue(const char* key, int64 value);
79 // Retrieves the value associated with the given key. This will use sqlite's
80 // type conversion rules. It will return true on success.
81 bool GetValue(const char* key, std::string* value);
82 bool GetValue(const char* key, int* value);
83 bool GetValue(const char* key, int64* value);
85 // Deletes the key from the table.
86 bool DeleteKey(const char* key);
89 // Conveniences to prepare the two types of statements used by
91 void PrepareSetStatement(Statement* statement, const char* key);
92 bool PrepareGetStatement(Statement* statement, const char* key);
96 DISALLOW_COPY_AND_ASSIGN(MetaTable);
101 #endif // SQL_META_TABLE_H_