1MONGOC_CLIENT_READ_COMMAND_WITH_OPTSl(i3b)moMnOgNoGcOC_CLIENT_READ_COMMAND_WITH_OPTS(3)
2
6 mongoc_client_read_command_with_opts - mongoc_client_read_com‐
7 mand_with_opts()
8
10 bool
11 mongoc_client_read_command_with_opts (mongoc_client_t *client,
12 const char *db_name,
13 const bson_t *command,
14 const mongoc_read_prefs_t *read_prefs,
15 const bson_t *opts,
16 bson_t *reply,
17 bson_error_t *error);
18 Execute a command on the server, applying logic that is specific to
20 commands that read, and taking the MongoDB server version into account.
21 To send a raw command to the server without any of this logic, use mon‐
22 goc_client_command_simple.
23 Use this function for commands that read such as "count" or "distinct".
25 Read preferences, read concern, and collation can be overridden by var‐
27 ious sources. In a transaction, read concern and write concern are pro‐
28 hibited in opts and the read preference must be primary or NULL. The
29 highest-priority sources for these options are listed first in the fol‐
30 lowing table. No write concern is applied.
31 ┌─────────────────┬──────────────┬───────────┐
33 │Read Preferences │ Read Concern │ Collation │
34 ├─────────────────┼──────────────┼───────────┤
35 │read_prefs │ opts │ opts │
36 ├─────────────────┼──────────────┼───────────┤
37 │Transaction │ Transaction │ │
38 ├─────────────────┼──────────────┼───────────┤
39 │client │ │ │
40 └─────────────────┴──────────────┴───────────┘
41 See the example for transactions and for the "distinct" command with
43 opts.
44 reply is always initialized, and must be freed with bson_destroy().
46 This function is considered a retryable read operation. Upon a tran‐
48 sient error (a network error, errors due to replica set failover, etc.)
49 the operation is safely retried once. If retryreads is false in the
50 URI (see mongoc_uri_t) the retry behavior does not apply.
51 Retry logic occurs regardless of the underlying command. Retrying
53 mapReduce has the potential for degraded performance. Retrying a get‐
54 More command has the potential to miss results. For those commands, use
55 generic command helpers (like mongoc_client_command_with_opts) instead.
56
58 · client: A mongoc_client_t.
59 · db_name: The name of the database to run the command on.
61 · command: A bson_t containing the command specification.
63 · read_prefs: An optional mongoc_read_prefs_t.
65 · opts: A bson_t containing additional options.
67 · reply: A location for the resulting document.
69 · error: An optional location for a bson_error_t or NULL.
71 opts may be NULL or a BSON document with additional command options:
73 · readConcern: Construct a mongoc_read_concern_t and use mon‐
75 goc_read_concern_append to add the read concern to opts. See the
76 example code for mongoc_client_read_command_with_opts. Read concern
77 requires MongoDB 3.2 or later, otherwise an error is returned.
78 · sessionId: First, construct a mongoc_client_session_t with mon‐
80 goc_client_start_session. You can begin a transaction with mon‐
81 goc_client_session_start_transaction, optionally with a mongoc_trans‐
82 action_opt_t that overrides the options inherited from client, and
83 use mongoc_client_session_append to add the session to opts. See the
84 example code for mongoc_client_session_t.
85 · collation: Configure textual comparisons. See Setting Collation
87 Order, and the MongoDB Manual entry on Collation. Collation requires
88 MongoDB 3.2 or later, otherwise an error is returned.
89 · serverId: To target a specific server, include an int32 "serverId"
91 field. Obtain the id by calling mongoc_client_select_server, then
92 mongoc_server_description_id on its return value.
93 Consult the MongoDB Manual entry on Database Commands for each com‐
95 mand's arguments.
96
98 Errors are propagated via the error parameter.
99
101 Returns true if successful. Returns false and sets error if there are
102 invalid arguments or a server or network error.
103
105 example-command-with-opts.c.INDENT 0.0
106 /*
108 Demonstrates how to prepare options for mongoc_client_read_command_with_opts and
110 mongoc_client_write_command_with_opts. First it calls "cloneCollectionAsCapped"
111 command with "writeConcern" option, then "distinct" command with "collation" and
112 "readConcern" options,
113 Start a MongoDB 3.4 replica set with --enableMajorityReadConcern and insert two
115 documents:
116 $ mongo
118 MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 1, y: "One"})
119 WriteResult({ "nInserted" : 1 })
120 MongoDB Enterprise replset:PRIMARY> db.my_collection.insert({x: 2, y: "Two"})
121 WriteResult({ "nInserted" : 1 })
122 Build and run the example:
124 gcc example-command-with-opts.c -o example-command-with-opts $(pkg-config
126 --cflags --libs libmongoc-1.0)
127 ./example-command-with-opts [CONNECTION_STRING]
128 cloneCollectionAsCapped: { "ok" : 1 }
129 distinct: { "values" : [ 1, 2 ], "ok" : 1 }
130 */
132 #include <mongoc/mongoc.h>
134 #include <stdio.h>
135 #include <stdlib.h>
136 int
138 main (int argc, char *argv[])
139 {
140 mongoc_client_t *client;
141 const char *uri_string = "mongodb://127.0.0.1/?appname=client-example";
142 mongoc_uri_t *uri;
143 bson_t *cmd;
144 bson_t *opts;
145 mongoc_write_concern_t *write_concern;
146 mongoc_read_prefs_t *read_prefs;
147 mongoc_read_concern_t *read_concern;
148 bson_t reply;
149 bson_error_t error;
150 char *json;
151 mongoc_init ();
153 if (argc > 1) {
155 uri_string = argv[1];
156 }
157 uri = mongoc_uri_new_with_error (uri_string, &error);
159 if (!uri) {
160 fprintf (stderr,
161 "failed to parse URI: %s\n"
162 "error message: %s\n",
163 uri_string,
164 error.message);
165 return EXIT_FAILURE;
166 }
167 client = mongoc_client_new_from_uri (uri);
169 if (!client) {
170 return EXIT_FAILURE;
171 }
172 mongoc_client_set_error_api (client, 2);
174 cmd = BCON_NEW ("cloneCollectionAsCapped",
176 BCON_UTF8 ("my_collection"),
177 "toCollection",
178 BCON_UTF8 ("my_capped_collection"),
179 "size",
180 BCON_INT64 (1024 * 1024));
181 /* include write concern "majority" in command options */
183 write_concern = mongoc_write_concern_new ();
184 mongoc_write_concern_set_wmajority (write_concern, 10000 /* wtimeoutMS */);
185 opts = bson_new ();
186 mongoc_write_concern_append (write_concern, opts);
187 if (mongoc_client_write_command_with_opts (
189 client, "test", cmd, opts, &reply, &error)) {
190 json = bson_as_canonical_extended_json (&reply, NULL);
191 printf ("cloneCollectionAsCapped: %s\n", json);
192 bson_free (json);
193 } else {
194 fprintf (stderr, "cloneCollectionAsCapped: %s\n", error.message);
195 }
196 bson_free (cmd);
198 bson_free (opts);
199 /* distinct values of "x" in "my_collection" where "y" sorts after "one" */
201 cmd = BCON_NEW ("distinct",
202 BCON_UTF8 ("my_collection"),
203 "key",
204 BCON_UTF8 ("x"),
205 "query",
206 "{",
207 "y",
208 "{",
209 "$gt",
210 BCON_UTF8 ("one"),
211 "}",
212 "}");
213 read_prefs = mongoc_read_prefs_new (MONGOC_READ_SECONDARY);
215 /* "One" normally sorts before "one"; make "One" sort after "one" */
217 opts = BCON_NEW ("collation",
218 "{",
219 "locale",
220 BCON_UTF8 ("en_US"),
221 "caseFirst",
222 BCON_UTF8 ("lower"),
223 "}");
224 /* add a read concern to "opts" */
226 read_concern = mongoc_read_concern_new ();
227 mongoc_read_concern_set_level (read_concern,
228 MONGOC_READ_CONCERN_LEVEL_MAJORITY);
229 mongoc_read_concern_append (read_concern, opts);
231 if (mongoc_client_read_command_with_opts (
233 client, "test", cmd, read_prefs, opts, &reply, &error)) {
234 json = bson_as_canonical_extended_json (&reply, NULL);
235 printf ("distinct: %s\n", json);
236 bson_free (json);
237 } else {
238 fprintf (stderr, "distinct: %s\n", error.message);
239 }
240 bson_destroy (cmd);
242 bson_destroy (opts);
243 bson_destroy (&reply);
244 mongoc_read_prefs_destroy (read_prefs);
245 mongoc_read_concern_destroy (read_concern);
246 mongoc_write_concern_destroy (write_concern);
247 mongoc_uri_destroy (uri);
248 mongoc_client_destroy (client);
249 mongoc_cleanup ();
251 return EXIT_SUCCESS;
253 }
254
257 MongoDB, Inc
258
260 2017-present, MongoDB, Inc
2611.16.2 Feb 25,MO2N0G2O0C_CLIENT_READ_COMMAND_WITH_OPTS(3)