| // Copyright 2013 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_RECOVERY_H_ |
| #define SQL_RECOVERY_H_ |
| |
| #include <stddef.h> |
| |
| #include <memory> |
| |
| #include "base/macros.h" |
| #include "sql/connection.h" |
| |
| namespace base { |
| class FilePath; |
| } |
| |
| namespace sql { |
| |
| // Recovery module for sql/. The basic idea is to create a fresh |
| // database and populate it with the recovered contents of the |
| // original database. If recovery is successful, the recovered |
| // database is backed up over the original database. If recovery is |
| // not successful, the original database is razed. In either case, |
| // the original handle is poisoned so that operations on the stack do |
| // not accidentally disrupt the restored data. |
| // |
| // { |
| // std::unique_ptr<sql::Recovery> r = |
| // sql::Recovery::Begin(orig_db, orig_db_path); |
| // if (r) { |
| // // Create the schema to recover to. On failure, clear the |
| // // database. |
| // if (!r.db()->Execute(kCreateSchemaSql)) { |
| // sql::Recovery::Unrecoverable(std::move(r)); |
| // return; |
| // } |
| // |
| // // Recover data in "mytable". |
| // size_t rows_recovered = 0; |
| // if (!r.AutoRecoverTable("mytable", 0, &rows_recovered)) { |
| // sql::Recovery::Unrecoverable(std::move(r)); |
| // return; |
| // } |
| // |
| // // Manually cleanup additional constraints. |
| // if (!r.db()->Execute(kCleanupSql)) { |
| // sql::Recovery::Unrecoverable(std::move(r)); |
| // return; |
| // } |
| // |
| // // Commit the recovered data to the original database file. |
| // sql::Recovery::Recovered(std::move(r)); |
| // } |
| // } |
| // |
| // If Recovered() is not called, then RazeAndClose() is called on |
| // orig_db. |
| |
| class SQL_EXPORT Recovery { |
| public: |
| ~Recovery(); |
| |
| // This module is intended to be used in concert with a virtual |
| // table module (see third_party/sqlite/src/src/recover.c). If the |
| // build defines USE_SYSTEM_SQLITE, this module will not be present. |
| // TODO(shess): I am still debating how to handle this - perhaps it |
| // will just imply Unrecoverable(). This is exposed to allow tests |
| // to adapt to the cases, please do not rely on it in production |
| // code. |
| static bool FullRecoverySupported(); |
| |
| // Begin the recovery process by opening a temporary database handle |
| // and attach the existing database to it at "corrupt". To prevent |
| // deadlock, all transactions on |connection| are rolled back. |
| // |
| // Returns NULL in case of failure, with no cleanup done on the |
| // original connection (except for breaking the transactions). The |
| // caller should Raze() or otherwise cleanup as appropriate. |
| // |
| // TODO(shess): Later versions of SQLite allow extracting the path |
| // from the connection. |
| // TODO(shess): Allow specifying the connection point? |
| static std::unique_ptr<Recovery> Begin(Connection* connection, |
| const base::FilePath& db_path) |
| WARN_UNUSED_RESULT; |
| |
| // Mark recovery completed by replicating the recovery database over |
| // the original database, then closing the recovery database. The |
| // original database handle is poisoned, causing future calls |
| // against it to fail. |
| // |
| // If Recovered() is not called, the destructor will call |
| // Unrecoverable(). |
| // |
| // TODO(shess): At this time, this function can fail while leaving |
| // the original database intact. Figure out which failure cases |
| // should go to RazeAndClose() instead. |
| static bool Recovered(std::unique_ptr<Recovery> r) WARN_UNUSED_RESULT; |
| |
| // Indicate that the database is unrecoverable. The original |
| // database is razed, and the handle poisoned. |
| static void Unrecoverable(std::unique_ptr<Recovery> r); |
| |
| // When initially developing recovery code, sometimes the possible |
| // database states are not well-understood without further |
| // diagnostics. Abandon recovery but do not raze the original |
| // database. |
| // NOTE(shess): Only call this when adding recovery support. In the |
| // steady state, all databases should progress to recovered or razed. |
| static void Rollback(std::unique_ptr<Recovery> r); |
| |
| // Handle to the temporary recovery database. |
| sql::Connection* db() { return &recover_db_; } |
| |
| // Attempt to recover the named table from the corrupt database into |
| // the recovery database using a temporary recover virtual table. |
| // The virtual table schema is derived from the named table's schema |
| // in database [main]. Data is copied using INSERT OR IGNORE, so |
| // duplicates are dropped. |
| // |
| // If the source table has fewer columns than the target, the target |
| // DEFAULT value will be used for those columns. |
| // |
| // Returns true if all operations succeeded, with the number of rows |
| // recovered in |*rows_recovered|. |
| // |
| // NOTE(shess): Due to a flaw in the recovery virtual table, at this |
| // time this code injects the DEFAULT value of the target table in |
| // locations where the recovery table returns NULL. This is not |
| // entirely correct, because it happens both when there is a short |
| // row (correct) but also where there is an actual NULL value |
| // (incorrect). |
| // |
| // TODO(shess): Flag for INSERT OR REPLACE vs IGNORE. |
| // TODO(shess): Handle extended table names. |
| bool AutoRecoverTable(const char* table_name, size_t* rows_recovered); |
| |
| // Setup a recover virtual table at temp.recover_meta, reading from |
| // corrupt.meta. Returns true if created. |
| // TODO(shess): Perhaps integrate into Begin(). |
| // TODO(shess): Add helpers to fetch additional items from the meta |
| // table as needed. |
| bool SetupMeta(); |
| |
| // Fetch the version number from temp.recover_meta. Returns false |
| // if the query fails, or if there is no version row. Otherwise |
| // returns true, with the version in |*version_number|. |
| // |
| // Only valid to call after successful SetupMeta(). |
| bool GetMetaVersionNumber(int* version_number); |
| |
| private: |
| explicit Recovery(Connection* connection); |
| |
| // Setup the recovery database handle for Begin(). Returns false in |
| // case anything failed. |
| bool Init(const base::FilePath& db_path) WARN_UNUSED_RESULT; |
| |
| // Copy the recovered database over the original database. |
| bool Backup() WARN_UNUSED_RESULT; |
| |
| // Close the recovery database, and poison the original handle. |
| // |raze| controls whether the original database is razed or just |
| // poisoned. |
| enum Disposition { |
| RAZE_AND_POISON, |
| POISON, |
| }; |
| void Shutdown(Disposition raze); |
| |
| Connection* db_; // Original database connection. |
| Connection recover_db_; // Recovery connection. |
| |
| DISALLOW_COPY_AND_ASSIGN(Recovery); |
| }; |
| |
| } // namespace sql |
| |
| #endif // SQL_RECOVERY_H_ |