focal (3) mongoc_database_read_command_with_opts.3.gz
NAME
mongoc_database_read_command_with_opts - 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
• database: A mongoc_database_t.
• command: A bson_t containing the command specification.
• read_prefs: An optional mongoc_read_prefs_t.
• opts: A bson_t containing additional options.
• reply: A location for the resulting document.
• error: An optional location for a bson_error_t or NULL.
opts may be NULL or a BSON document with additional command options:
• readConcern: Construct a mongoc_read_concern_t and use mongoc_read_concern_append to add the read
concern to opts. See the example code for mongoc_client_read_command_with_opts. Read concern requires
MongoDB 3.2 or later, otherwise an error is returned.
• sessionId: First, construct a mongoc_client_session_t with mongoc_client_start_session. You can begin a
transaction with mongoc_client_session_start_transaction, optionally with a mongoc_transaction_opt_t
that overrides the options inherited from database, and use mongoc_client_session_append to add the
session to opts. See the example code for mongoc_client_session_t.
• collation: Configure textual comparisons. See Setting Collation Order, and the MongoDB Manual entry on
Collation. Collation requires MongoDB 3.2 or later, otherwise an error is returned.
• serverId: To target a specific server, include an int32 "serverId" field. Obtain the id by calling
mongoc_client_select_server, then mongoc_server_description_id on its return value.
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.
AUTHOR
MongoDB, Inc
COPYRIGHT
2017-present, MongoDB, Inc