Record A Database Snapshot

int sqlite3_snapshot_get(
  sqlite3 *db,
  const char *zSchema,
  sqlite3_snapshot **ppSnapshot

The sqlite3_snapshot_get(D,S,P) interface attempts to make a new sqlite3_snapshot object that records the current state of schema S in database connection D. On success, the sqlite3_snapshot_get(D,S,P) interface writes a pointer to the newly created sqlite3_snapshot object into *P and returns SQLITE_OK. If there is not already a read-transaction open on schema S when this function is called, one is opened automatically.

The following must be true for this function to succeed. If any of the following statements are false when sqlite3_snapshot_get() is called, SQLITE_ERROR is returned. The final value of *P is undefined in this case.

  • The database handle must not be in autocommit mode.
  • Schema S of database connection D must be a WAL mode database.
  • There must not be a write transaction open on schema S of database connection D.
  • One or more transactions must have been written to the current wal file since it was created on disk (by any connection). This means that a snapshot cannot be taken on a wal mode database with no wal file immediately after it is first opened. At least one transaction must be written to it first.

This function may also return SQLITE_NOMEM. If it is called with the database handle in autocommit mode but fails for some other reason, whether or not a read transaction is opened on schema S is undefined.

The sqlite3_snapshot object returned from a successful call to sqlite3_snapshot_get() must be freed using sqlite3_snapshot_free() to avoid a memory leak.

The sqlite3_snapshot_get() interface is only available when the SQLITE_ENABLE_SNAPSHOT compile-time option is used.

See also lists of Objects, Constants, and Functions.

SQLite is in the Public Domain.