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Command: sqlite3_snapshot_open | Section: 3 | Source: NetBSD | File: sqlite3_snapshot_open.3
SQLITE3_SNAPSHOT_OPEN(3) FreeBSD Library Functions Manual
NAME
sqlite3_snapshot_open - Start a read transaction on an historical
snapshot
SYNOPSIS
int
sqlite3_snapshot_open(sqlite3 *db, const char *zSchema,
sqlite3_snapshot *pSnapshot );
DESCRIPTION
The sqlite3_snapshot_open(D,S,P) interface either starts a new read
transaction or upgrades an existing one for schema S of database
connection D such that the read transaction refers to historical snapshot
P, rather than the most recent change to the database. The
sqlite3_snapshot_open() interface returns SQLITE_OK on success or an
appropriate error code if it fails.
In order to succeed, the database connection must not be in autocommit
mode when sqlite3_snapshot_open(D,S,P) is called. If there is already a
read transaction open on schema S, then the database handle must have no
active statements (SELECT statements that have been passed to
sqlite3_step() but not sqlite3_reset() or sqlite3_finalize()).
SQLITE_ERROR is returned if either of these conditions is violated, or if
schema S does not exist, or if the snapshot object is invalid.
A call to sqlite3_snapshot_open() will fail to open if the specified
snapshot has been overwritten by a checkpoint. In this case
SQLITE_ERROR_SNAPSHOT is returned.
If there is already a read transaction open when this function is
invoked, then the same read transaction remains open (on the same
database snapshot) if SQLITE_ERROR, SQLITE_BUSY or SQLITE_ERROR_SNAPSHOT
is returned. If another error code - for example SQLITE_PROTOCOL or an
SQLITE_IOERR error code - is returned, then the final state of the read
transaction is undefined. If SQLITE_OK is returned, then the read
transaction is now open on database snapshot P.
A call to sqlite3_snapshot_open(D,S,P) will fail if the database
connection D does not know that the database file for schema S is in WAL
mode. A database connection might not know that the database file is in
WAL mode if there has been no prior I/O on that database connection, or
if the database entered WAL mode after the most recent I/O on the
database connection. (Hint: Run "PRAGMA application_id" against a newly
opened database connection in order to make it ready to use snapshots.)
The sqlite3_snapshot_open() interface is only available when the
SQLITE_ENABLE_SNAPSHOT compile-time option is used.
SEE ALSO
sqlite3_get_autocommit(3), sqlite3(3), sqlite3_snapshot(3),
sqlite3_snapshot_open(3)
FreeBSD 14.1-RELEASE-p8 December 19, 2018 FreeBSD 14.1-RELEASE-p8