1MONGOC_COMMON_TASK_EXAMPLES(3) MongoDB C Driver MONGOC_COMMON_TASK_EXAMPLES(3)
2
6 mongoc_common_task_examples - Common Tasks
7 Drivers for some other languages provide helper functions to perform
9 certain common tasks. In the C Driver we must explicitly build commands
10 to send to the server.
11 This snippet contains example code for the explain, copydb and
13 cloneCollection commands.
14
16 First we'll write some code to insert sample data: doc-com‐
17 mon-insert.c.INDENT 0.0
18 /* Don't try to compile this file on its own. It's meant to be #included
20 by example code */
21 /* Insert some sample data */
23 bool
24 insert_data (mongoc_collection_t *collection)
25 {
26 mongoc_bulk_operation_t *bulk;
27 enum N { ndocs = 4 };
28 bson_t *docs[ndocs];
29 bson_error_t error;
30 int i = 0;
31 bool ret;
32 bulk = mongoc_collection_create_bulk_operation_with_opts (collection, NULL);
34 docs[0] = BCON_NEW ("x", BCON_DOUBLE (1.0), "tags", "[", "dog", "cat", "]");
36 docs[1] = BCON_NEW ("x", BCON_DOUBLE (2.0), "tags", "[", "cat", "]");
37 docs[2] = BCON_NEW (
38 "x", BCON_DOUBLE (2.0), "tags", "[", "mouse", "cat", "dog", "]");
39 docs[3] = BCON_NEW ("x", BCON_DOUBLE (3.0), "tags", "[", "]");
40 for (i = 0; i < ndocs; i++) {
42 mongoc_bulk_operation_insert (bulk, docs[i]);
43 bson_destroy (docs[i]);
44 docs[i] = NULL;
45 }
46 ret = mongoc_bulk_operation_execute (bulk, NULL, &error);
48 if (!ret) {
50 fprintf (stderr, "Error inserting data: %s\n", error.message);
51 }
52 mongoc_bulk_operation_destroy (bulk);
54 return ret;
55 }
56 /* A helper which we'll use a lot later on */
58 void
59 print_res (const bson_t *reply)
60 {
61 char *str;
62 BSON_ASSERT (reply);
63 str = bson_as_canonical_extended_json (reply, NULL);
64 printf ("%s\n", str);
65 bson_free (str);
66 }
67
70 This is how to use the explain command in MongoDB 3.2+:
71 explain.c.INDENT 0.0
72 bool
74 explain (mongoc_collection_t *collection)
75 {
76 bson_t *command;
77 bson_t reply;
78 bson_error_t error;
79 bool res;
80 command = BCON_NEW ("explain",
82 "{",
83 "find",
84 BCON_UTF8 (COLLECTION_NAME),
85 "filter",
86 "{",
87 "x",
88 BCON_INT32 (1),
89 "}",
90 "}");
91 res = mongoc_collection_command_simple (
92 collection, command, NULL, &reply, &error);
93 if (!res) {
94 fprintf (stderr, "Error with explain: %s\n", error.message);
95 goto cleanup;
96 }
97 /* Do something with the reply */
99 print_res (&reply);
100 cleanup:
102 bson_destroy (&reply);
103 bson_destroy (command);
104 return res;
105 }
106
109 This example requires two instances of mongo to be running.
110 Here's how to use the copydb command to copy a database from another
112 instance of MongoDB: copydb.c.INDENT 0.0
113 bool
115 copydb (mongoc_client_t *client, const char *other_host_and_port)
116 {
117 mongoc_database_t *admindb;
118 bson_t *command;
119 bson_t reply;
120 bson_error_t error;
121 bool res;
122 BSON_ASSERT (other_host_and_port);
124 /* Must do this from the admin db */
125 admindb = mongoc_client_get_database (client, "admin");
126 command = BCON_NEW ("copydb",
128 BCON_INT32 (1),
129 "fromdb",
130 BCON_UTF8 ("test"),
131 "todb",
132 BCON_UTF8 ("test2"),
133 /* If you want from a different host */
135 "fromhost",
136 BCON_UTF8 (other_host_and_port));
137 res =
138 mongoc_database_command_simple (admindb, command, NULL, &reply, &error);
139 if (!res) {
140 fprintf (stderr, "Error with copydb: %s\n", error.message);
141 goto cleanup;
142 }
143 /* Do something with the reply */
145 print_res (&reply);
146 cleanup:
148 bson_destroy (&reply);
149 bson_destroy (command);
150 mongoc_database_destroy (admindb);
151 return res;
153 }
154
157 This example requires two instances of mongo to be running.
158 Here's an example of the cloneCollection command to clone a collection
160 from another instance of MongoDB: clone-collection.c.INDENT 0.0
161 bool
163 clone_collection (mongoc_database_t *database, const char *other_host_and_port)
164 {
165 bson_t *command;
166 bson_t reply;
167 bson_error_t error;
168 bool res;
169 BSON_ASSERT (other_host_and_port);
171 command = BCON_NEW ("cloneCollection",
172 BCON_UTF8 ("test.remoteThings"),
173 "from",
174 BCON_UTF8 (other_host_and_port),
175 "query",
176 "{",
177 "x",
178 BCON_INT32 (1),
179 "}");
180 res =
181 mongoc_database_command_simple (database, command, NULL, &reply, &error);
182 if (!res) {
183 fprintf (stderr, "Error with clone: %s\n", error.message);
184 goto cleanup;
185 }
186 /* Do something with the reply */
188 print_res (&reply);
189 cleanup:
191 bson_destroy (&reply);
192 bson_destroy (command);
193 return res;
195 }
196
199 common-operations.c.INDENT 0.0
200 /*
202 * Copyright 2016 MongoDB, Inc.
203 *
204 * Licensed under the Apache License, Version 2.0 (the "License");
205 * you may not use this file except in compliance with the License.
206 * You may obtain a copy of the License at
207 *
208 * http://www.apache.org/licenses/LICENSE-2.0
209 *
210 * Unless required by applicable law or agreed to in writing, software
211 * distributed under the License is distributed on an "AS IS" BASIS,
212 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
213 * See the License for the specific language governing permissions and
214 * limitations under the License.
215 */
216 #include <mongoc/mongoc.h>
219 #include <stdio.h>
220 const char *COLLECTION_NAME = "things";
223 #include "../doc-common-insert.c"
225 #include "explain.c"
226 #include "copydb.c"
227 #include "clone-collection.c"
228 int
231 main (int argc, char *argv[])
232 {
233 mongoc_database_t *database = NULL;
234 mongoc_client_t *client = NULL;
235 mongoc_collection_t *collection = NULL;
236 mongoc_uri_t *uri = NULL;
237 bson_error_t error;
238 char *host_and_port;
239 int res = 0;
240 char *other_host_and_port = NULL;
241 if (argc < 2 || argc > 3) {
243 fprintf (stderr,
244 "usage: %s MONGOD-1-CONNECTION-STRING "
245 "[MONGOD-2-HOST-NAME:MONGOD-2-PORT]\n",
246 argv[0]);
247 fprintf (stderr,
248 "MONGOD-1-CONNECTION-STRING can be "
249 "of the following forms:\n");
250 fprintf (stderr, "localhost\t\t\t\tlocal machine\n");
251 fprintf (stderr, "localhost:27018\t\t\t\tlocal machine on port 27018\n");
252 fprintf (stderr,
253 "mongodb://user:pass@localhost:27017\t"
254 "local machine on port 27017, and authenticate with username "
255 "user and password pass\n");
256 return EXIT_FAILURE;
257 }
258 mongoc_init ();
260 if (strncmp (argv[1], "mongodb://", 10) == 0) {
262 host_and_port = bson_strdup (argv[1]);
263 } else {
264 host_and_port = bson_strdup_printf ("mongodb://%s", argv[1]);
265 }
266 other_host_and_port = argc > 2 ? argv[2] : NULL;
267 uri = mongoc_uri_new_with_error (host_and_port, &error);
269 if (!uri) {
270 fprintf (stderr,
271 "failed to parse URI: %s\n"
272 "error message: %s\n",
273 host_and_port,
274 error.message);
275 res = EXIT_FAILURE;
276 goto cleanup;
277 }
278 client = mongoc_client_new_from_uri (uri);
280 if (!client) {
281 res = EXIT_FAILURE;
282 goto cleanup;
283 }
284 mongoc_client_set_error_api (client, 2);
286 database = mongoc_client_get_database (client, "test");
287 collection = mongoc_database_get_collection (database, COLLECTION_NAME);
288 printf ("Inserting data\n");
290 if (!insert_data (collection)) {
291 res = EXIT_FAILURE;
292 goto cleanup;
293 }
294 printf ("explain\n");
296 if (!explain (collection)) {
297 res = EXIT_FAILURE;
298 goto cleanup;
299 }
300 if (other_host_and_port) {
302 printf ("copydb\n");
303 if (!copydb (client, other_host_and_port)) {
304 res = EXIT_FAILURE;
305 goto cleanup;
306 }
307 printf ("clone collection\n");
309 if (!clone_collection (database, other_host_and_port)) {
310 res = EXIT_FAILURE;
311 goto cleanup;
312 }
313 }
314 cleanup:
316 if (collection) {
317 mongoc_collection_destroy (collection);
318 }
319 if (database) {
321 mongoc_database_destroy (database);
322 }
323 if (client) {
325 mongoc_client_destroy (client);
326 }
327 if (uri) {
329 mongoc_uri_destroy (uri);
330 }
331 bson_free (host_and_port);
333 mongoc_cleanup ();
334 return res;
335 }
336First launch two separate instances of mongod (must be done from separate
339shells):
340 $ mongod
342 $ mkdir /tmp/db2$ mongod --dbpath /tmp/db2 --port 27018 # second instance
344 Now compile and run the example program:
346 $ cd examples/common_operations/$ gcc -Wall -o example common-operations.c $(pkg-config --cflags --libs libmongoc-1.0)$ ./example localhost:27017 localhost:27018
348 Inserting data
349 explain
350 {
351 "executionStats" : {
352 "allPlansExecution" : [],
353 "executionStages" : {
354 "advanced" : 19,
355 "direction" : "forward" ,
356 "docsExamined" : 76,
357 "executionTimeMillisEstimate" : 0,
358 "filter" : {
359 "x" : {
360 "$eq" : 1
361 }
362 },
363 "invalidates" : 0,
364 "isEOF" : 1,
365 "nReturned" : 19,
366 "needTime" : 58,
367 "needYield" : 0,
368 "restoreState" : 0,
369 "saveState" : 0,
370 "stage" : "COLLSCAN" ,
371 "works" : 78
372 },
373 "executionSuccess" : true,
374 "executionTimeMillis" : 0,
375 "nReturned" : 19,
376 "totalDocsExamined" : 76,
377 "totalKeysExamined" : 0
378 },
379 "ok" : 1,
380 "queryPlanner" : {
381 "indexFilterSet" : false,
382 "namespace" : "test.things",
383 "parsedQuery" : {
384 "x" : {
385 "$eq" : 1
386 }
387 },
388 "plannerVersion" : 1,
389 "rejectedPlans" : [],
390 "winningPlan" : {
391 "direction" : "forward" ,
392 "filter" : {
393 "x" : {
394 "$eq" : 1
395 }
396 },
397 "stage" : "COLLSCAN"
398 }
399 },
400 "serverInfo" : {
401 "gitVersion" : "05552b562c7a0b3143a729aaa0838e558dc49b25" ,
402 "host" : "MacBook-Pro-57.local",
403 "port" : 27017,
404 "version" : "3.2.6"
405 }
406 }
407 copydb
408 { "ok" : 1 }
409 clone collection
410 { "ok" : 1 }
411
413 MongoDB, Inc
414
416 2017-present, MongoDB, Inc
4171.13.1 Jan 24, 2019 MONGOC_COMMON_TASK_EXAMPLES(3)