void mongoc_session_opts_set_default_transaction_opts ( mongoc_session_opt_t *opts, const mongoc_transaction_opt_t *txn_opts);
Set the default options for transactions started with this session. The txn_opts argument is copied and can be freed after calling this function.
When a session is first created with mongoc_client_start_session, it inherits from the client the read concern, write concern, and read preference with which to start transactions. Each of these fields can be overridden independently. Create a mongoc_transaction_opt_t with mongoc_transaction_opts_new, and pass a non-NULL option to any of the mongoc_transaction_opt_t setter functions:
Pass the resulting transaction options to mongoc_session_opts_set_default_transaction_opts. Each field set in the transaction options overrides the inherited client configuration. There is an opportunity to override each one of these fields again by passing a mongoc_transaction_opt_t to mongoc_client_session_start_transaction.
- opts: A mongoc_session_opt_t.
- txn_opts: A mongoc_transaction_opt_t.
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