bionic (3) mongoc_client_read_command_with_opts.3.gz
NAME
mongoc_client_read_command_with_opts - mongoc_client_read_command_with_opts()
SYNOPSIS
bool
mongoc_client_read_command_with_opts (mongoc_client_t *client,
const char *db_name,
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_client_command_simple.
Use this function for commands that read such as "count" or "distinct". Read concern is applied from opts
or else from client. Collation is applied from opts (see example below). Read preferences are applied
from read_prefs or else from client. No write concern is applied.
reply is always initialized, and must be freed with bson_destroy().
PARAMETERS
• client: A mongoc_client_t.
• db_name: The name of the database to run the command on.
• 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: Construct a mongoc_client_session_t with mongoc_client_start_session 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
example-command-with-opts.c.INDENT 0.0
/*
Demonstrates how to prepare options for mongoc_client_read_command_with_opts and
mongoc_client_write_command_with_opts. First it calls "cloneCollectionAsCapped"
command with "writeConcern" option, then "distinct" command with "collation" and
"readConcern" options,
Start a MongoDB 3.4 replica set with --enableMajorityReadConcern and insert two
documents:
$ mongo
MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 1, y: "One"})
WriteResult({ "nInserted" : 1 })
MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 2, y: "Two"})
WriteResult({ "nInserted" : 1 })
Build and run the example:
gcc example-command-with-opts.c -o example-command-with-opts $(pkg-config
--cflags --libs libmongoc-1.0)
./example-command-with-opts [CONNECTION_STRING]
cloneCollectionAsCapped: { "ok" : 1 }
distinct: { "values" : [ 1, 2 ], "ok" : 1 }
*/
#include <mongoc.h>
#include <stdio.h>
#include <stdlib.h>
int
main (int argc, char *argv[])
{
mongoc_client_t *client;
const char *uristr = "mongodb://127.0.0.1/?appname=client-example";
bson_t *cmd;
bson_t *opts;
mongoc_write_concern_t *write_concern;
mongoc_read_prefs_t *read_prefs;
mongoc_read_concern_t *read_concern;
bson_t reply;
bson_error_t error;
char *json;
mongoc_init ();
if (argc > 1) {
uristr = argv[1];
}
client = mongoc_client_new (uristr);
if (!client) {
fprintf (stderr, "Failed to parse URI.\n");
return EXIT_FAILURE;
}
mongoc_client_set_error_api (client, 2);
cmd = BCON_NEW ("cloneCollectionAsCapped",
BCON_UTF8 ("my_collection"),
"toCollection",
BCON_UTF8 ("my_capped_collection"),
"size",
BCON_INT64 (1024 * 1024));
/* include write concern "majority" in command options */
write_concern = mongoc_write_concern_new ();
mongoc_write_concern_set_wmajority (write_concern, 10000 /* wtimeoutMS */);
opts = bson_new ();
mongoc_write_concern_append (write_concern, opts);
if (mongoc_client_write_command_with_opts (
client, "test", cmd, opts, &reply, &error)) {
json = bson_as_canonical_extended_json (&reply, NULL);
printf ("cloneCollectionAsCapped: %s\n", json);
bson_free (json);
} else {
fprintf (stderr, "cloneCollectionAsCapped: %s\n", error.message);
}
bson_free (cmd);
bson_free (opts);
/* distinct values of "x" in "my_collection" where "y" sorts after "one" */
cmd = BCON_NEW ("distinct",
BCON_UTF8 ("my_collection"),
"key",
BCON_UTF8 ("x"),
"query",
"{",
"y",
"{",
"$gt",
BCON_UTF8 ("one"),
"}",
"}");
read_prefs = mongoc_read_prefs_new (MONGOC_READ_SECONDARY);
/* "One" normally sorts before "one"; make "One" sort after "one" */
opts = BCON_NEW ("collation",
"{",
"locale",
BCON_UTF8 ("en_US"),
"caseFirst",
BCON_UTF8 ("lower"),
"}");
/* add a read concern to "opts" */
read_concern = mongoc_read_concern_new ();
mongoc_read_concern_set_level (read_concern,
MONGOC_READ_CONCERN_LEVEL_MAJORITY);
mongoc_read_concern_append (read_concern, opts);
if (mongoc_client_read_command_with_opts (
client, "test", cmd, read_prefs, opts, &reply, &error)) {
json = bson_as_canonical_extended_json (&reply, NULL);
printf ("distinct: %s\n", json);
bson_free (json);
} else {
fprintf (stderr, "distinct: %s\n", error.message);
}
bson_destroy (cmd);
bson_destroy (opts);
bson_destroy (&reply);
mongoc_read_prefs_destroy (read_prefs);
mongoc_read_concern_destroy (read_concern);
mongoc_write_concern_destroy (write_concern);
mongoc_client_destroy (client);
mongoc_cleanup ();
return EXIT_SUCCESS;
}
AUTHOR
MongoDB, Inc
COPYRIGHT
2018, MongoDB, Inc