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Allow sqlite3_snapshot_open() to be called to change the snapshot after a

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read transaction is already open on database.

FossilOrigin-Name: 051ac0152048ef52723196c26ca5f2629dafb782aec1c66fc30531bf54335043
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dan
2018-08-06 17:12:36 +00:00
parent f018fd5284
commit fa3d4c19a9
11 changed files with 343 additions and 36 deletions
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src/sqlite.h.in
+26 -15
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@@ -9035,22 +9035,33 @@ SQLITE_EXPERIMENTAL int sqlite3_snapshot_get(
** CAPI3REF: Start a read transaction on an historical snapshot
** METHOD: sqlite3_snapshot
**
** ^The [sqlite3_snapshot_open(D,S,P)] interface starts a
** read transaction 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.
** ^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_BUSY_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_BUSY_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.
**
** ^In order to succeed, a call to [sqlite3_snapshot_open(D,S,P)] must be
** the first operation following the [BEGIN] that takes the schema S
** out of [autocommit mode].
** ^In other words, schema S must not currently be in
** a transaction for [sqlite3_snapshot_open(D,S,P)] to work, but the
** database connection D must be out of [autocommit mode].
** ^A [snapshot] will fail to open if it has been overwritten by a
** [checkpoint].
** ^(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