Database rollback using WAL

A device configured to recover a previous state of a database using a write-ahead log (WAL), the database comprising a first set of pages, the device comprising:

• a memory, wherein the database is configured to use the WAL into which a set of frames associated with the WAL has been recorded, the set of frames representing revised contents of a second set of pages of the database, each frame of the set of frames represents a revised content of a corresponding page of the database, the database is associated with checkpoint information indicating that revised content of at least one page of the database was transferred from the WAL to the database at a set of checkpoints, each checkpoint of the set of checkpoints corresponds to a point in time, each frame in the set of frames corresponds to one checkpoint of the set of checkpoints, the WAL comprises information allowing the frames to be chronologically ordered, and the device is adapted to access the database and the associated WAL and checkpoint information;
• and
• a processor configured to:
• select, in the set of frames associated with the WAL, a specific frame representing a specific revised content of a corresponding specific page of the database upon request, said specific frame corresponding to a checkpoint that chronologically precedes at least one other checkpoint in the set of checkpoints associated with the WAL;
• identify, in the set of frames associated with the WAL, a first subset of frames comprising the specific frame and thereto zero or more chronologically preceding frames;
• extract, from the first set of pages, a first subset of pages;
• extract, from the corresponding pages of the first subset of frames, a second subset of pages;
• extracting a previous state of the database using the WAL, wherein the previous state comprises the specific revised content of the specific page and the previous state is extracted based on the content of the first subset of pages and the revised content of the second subset of pages;
• identify, in the set of frames associated with the WAL, a second subset of frames comprising one or more chronologically subsequent frames to the specific frame, said second subset of frames corresponding to a third subset of pages;
• determine whether the third subset of pages comprises at least one page that is not part of the second subset of pages;
• and
• indicate that the previous state is not a true previous state upon determining that the third subset of pages comprises at least one page that is not part of the second subset of pages.

A computer-readable storage media comprising instructions that when executed by a processor cause the processor to perform a method comprising:

• selecting, in a set of frames associated with a write-ahead log (WAL), a specific frame representing a specific revised content of a corresponding specific page of a database, said specific frame corresponding to a checkpoint that chronologically precedes at least one other checkpoint in a set of checkpoints associated with the WAL, wherein the database comprises a first set of pages, the database is a SQLite database or a derivative thereof, the database is configured to use the WAL into which the set of frames has been recorded, the set of frames representing revised contents of a second set of pages of the database, each frame of the set of frames represents a revised content of a corresponding page of the database, the database is further associated with checkpoint information indicating that revised content of at least one page of the database was transferred from the WAL to the database at the set of checkpoints, each checkpoint of the set of checkpoints corresponds to a point in time, each frame in the set of frames corresponds to one checkpoint of the set of checkpoints, and the WAL comprises information allowing the frames to be chronologically ordered;
• identifying, in the set of frames associated with the WAL, a first subset of frames comprising the specific frame and thereto zero or more chronologically preceding frames;
• extracting, from the first set of pages, a first subset of pages;
• extracting, from the corresponding pages of the first subset of frames, a second subset of pages;
• extracting a previous state of the database using the WAL, wherein the previous state comprises the specific revised content of the specific page and the previous state is extracted based on the content of the first subset of pages and the revised content of the second subset of pages, the specific frame corresponds to a checkpoint that chronologically precedes at least one other checkpoint in the set of checkpoints associated with the WAL;
• identifying, in the set of frames associated with the WAL, a second subset of frames comprising one or more chronologically subsequent frames to the specific frame, said second subset of frames corresponding to a third subset of pages;
• determining whether the third subset of pages comprises at least one page that is not part of the second subset of pages;
• and
• indicating that the previous state is not a true previous state, upon determining that the third subset of pages comprises at least one page that is not part of the second subset of pages.