mongoc_database_read_command_with_opts()#

Synopsis#

bool
mongoc_database_read_command_with_opts (mongoc_database_t *database,
                                        const bson_t *command,
                                        const mongoc_read_prefs_t *read_prefs,
                                        const bson_t *opts,
                                        bson_t *reply,
                                        bson_error_t *error);

Execute a command on the server, applying logic that is specific to commands that read, and taking the MongoDB server version into account. To send a raw command to the server without any of this logic, use mongoc_database_command_simple().

Use this function for commands that read such as “count” or “distinct”.

Read preferences, read concern, and collation can be overridden by various sources. In a transaction, read concern and write concern are prohibited in opts and the read preference must be primary or NULL. The highest-priority sources for these options are listed first in the following table. No write concern is applied.

Read Preferences

Read Concern

Collation

read_prefs

opts

opts

Transaction

Transaction

database

See the example for transactions and for the “distinct” command with opts.

reply is always initialized, and must be freed with bson_destroy().

This function is considered a retryable read operation. Upon a transient error (a network error, errors due to replica set failover, etc.) the operation is safely retried once. If retryreads is false in the URI (see mongoc_uri_t) the retry behavior does not apply.

Retry logic occurs regardless of the underlying command. Retrying mapReduce has the potential for degraded performance. Retrying a getMore command has the potential to miss results. For those commands, use generic command helpers (like mongoc_database_command_with_opts()) instead.

Parameters#

opts may be NULL or a BSON document with additional command options:

Consult the MongoDB Manual entry on Database Commands for each command’s arguments.

Errors#

Errors are propagated via the error parameter.

Returns#

Returns true if successful. Returns false and sets error if there are invalid arguments or a server or network error.

Example#

See the example code for mongoc_client_read_command_with_opts().