Hello, The documentation for sqlite3_snapshot_open() [1] says:
> A call to sqlite3_snapshot_open() will fail to open if the specified snapshot has been overwritten by a checkpoint. And indeed I am able to create a snapshot with sqlite3_snapshot_get() [2], then run checkpoints with sqlite3_wal_checkpoint_v2() [3], and finally have sqlite3_snapshot_open() fail. I have a concern, because this turns automatic checkpointing into a mortal danger for all snapshots. As soon as a checkpoint is performed, snapshots are invalidated, and whoever is relying on them has lost the database state he's interested into. My question is: is it possible to prevent checkpoints from completing successfully when a snapshot is alive? I know this is possible with a "hand-made checkpoint", made of a distinct connection which has started a deferred transaction and has performed an initial read. Such hand-made checkpoint has SQLITE_CHECKPOINT_RESTART and SQLITE_CHECKPOINT_TRUNCATE fail, and are still able to access their precious database state after a SQLITE_CHECKPOINT_PASSIVE or a SQLITE_CHECKPOINT_FULL. The behavior of those "hand-made checkpoint" matches well the needs of users who want to use WAL without thinking too much about it: they do not disable automatic checkpointing, and are guaranteed with a stable access to a given database state as long as they need it. I was wondering if such a behavior is possible with snapshots returned from sqlite3_snapshot_get(). If it is not, then I humbly suggest that this feature would be added, and am willing to listen to the opinion of SQLite experts on this subject. Regards, Gwendal Roué [1] https://www.sqlite.org/c3ref/snapshot_open.html [2] https://www.sqlite.org/c3ref/snapshot_get.html [3] https://www.sqlite.org/c3ref/wal_checkpoint_v2.html _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
