Function lmdb_master_sys::mdb_txn_begin

pub unsafe extern "C" fn mdb_txn_begin(
    env: *mut MDB_env,
    parent: *mut MDB_txn,
    flags: c_uint,
    txn: *mut *mut MDB_txn,
) -> c_int

Create a transaction for use with the environment.

The transaction handle may be discarded using #mdb_txn_abort() or #mdb_txn_commit().

Note: A transaction and its cursors must only be used by a single thread, and a thread may only have a single transaction at a time. If #MDB_NOTLS is in use, this does not apply to read-only transactions. Note: Cursors may not span transactions.

Arguments

• env (direction in) - An environment handle returned by #mdb_env_create()
• parent (direction in) - If this parameter is non-NULL, the new transaction will be a nested transaction, with the transaction indicated by parent as its parent. Transactions may be nested to any level. A parent transaction and its cursors may not issue any other operations than mdb_txn_commit and mdb_txn_abort while it has active child transactions.
• flags (direction in) - Special options for this transaction. This parameter must be set to 0 or by bitwise OR’ing together one or more of the values described here.

• #MDB_RDONLY This transaction will not perform any write operations.
• #MDB_NOSYNC Don't flush system buffers to disk when committing this transaction.
• #MDB_NOMETASYNC Flush system buffers but omit metadata flush when committing this transaction.

* `txn` (direction out) - Address where the new #MDB_txn handle will be stored # Returns

A non-zero error value on failure and 0 on success. Some possible errors are:

• #MDB_PANIC - a fatal error occurred earlier and the environment must be shut down.
• #MDB_MAP_RESIZED - another process wrote data beyond this MDB_env's mapsize and this environment's map must be resized as well. See #mdb_env_set_mapsize().
• #MDB_READERS_FULL - a read-only transaction was requested and the reader lock table is full. See #mdb_env_set_maxreaders().
• ENOMEM - out of memory.