1MONGOC_DATABASE_AGGREGATE(3) libmongoc MONGOC_DATABASE_AGGREGATE(3)
2
6 mongoc_database_aggregate - mongoc_database_aggregate()
7
9 mongoc_cursor_t *
10 mongoc_database_aggregate (mongoc_database_t *database,
11 const bson_t *pipeline,
12 const bson_t *opts,
13 const mongoc_read_prefs_t *read_prefs)
14 BSON_GNUC_WARN_UNUSED_RESULT;
15
17 · database: A mongoc_database_t.
18 · pipeline: A bson_t, either a BSON array or a BSON document containing
20 an array field named "pipeline".
21 · opts: A bson_t containing options for the command, or NULL.
23 · read_prefs: A mongoc_read_prefs_t or NULL.
25 opts may be NULL or a BSON document with additional command options:
27 · readConcern: Construct a mongoc_read_concern_t and use mon‐
29 goc_read_concern_append to add the read concern to opts. See the
30 example code for mongoc_client_read_command_with_opts. Read concern
31 requires MongoDB 3.2 or later, otherwise an error is returned.
32 · writeConcern: Construct a mongoc_write_concern_t and use mon‐
34 goc_write_concern_append to add the write concern to opts. See the
35 example code for mongoc_client_write_command_with_opts.
36 · sessionId: First, construct a mongoc_client_session_t with mon‐
38 goc_client_start_session. You can begin a transaction with mon‐
39 goc_client_session_start_transaction, optionally with a mongoc_trans‐
40 action_opt_t that overrides the options inherited from database, and
41 use mongoc_client_session_append to add the session to opts. See the
42 example code for mongoc_client_session_t.
43 · bypassDocumentValidation: Set to true to skip server-side schema val‐
45 idation of the provided BSON documents.
46 · collation: Configure textual comparisons. See Setting Collation
48 Order, and the MongoDB Manual entry on Collation. Collation requires
49 MongoDB 3.2 or later, otherwise an error is returned.
50 · serverId: To target a specific server, include an int32 "serverId"
52 field. Obtain the id by calling mongoc_client_select_server, then
53 mongoc_server_description_id on its return value.
54 · batchSize: An int32 representing number of documents requested to be
56 returned on each call to mongoc_cursor_next
57 For a list of all options, see the MongoDB Manual entry on the aggre‐
59 gate command.
60
62 This function creates a cursor which sends the aggregate command on the
63 underlying database upon the first call to mongoc_cursor_next(). For
64 more information on building aggregation pipelines, see the MongoDB
65 Manual entry on the aggregate command. Note that the pipeline must
66 start with a compatible stage that does not require an underlying col‐
67 lection (e.g. "$currentOp", "$listLocalSessions").
68 Read preferences, read and write concern, and collation can be overrid‐
70 den by various sources. The highest-priority sources for these options
71 are listed first in the following table. In a transaction, read concern
72 and write concern are prohibited in opts and the read preference must
73 be primary or NULL. Write concern is applied from opts, or if opts has
74 no write concern and the aggregation pipeline includes "$out", the
75 write concern is applied from database.
76 ┌─────────────────┬──────────────┬───────────────┬───────────┐
78 │Read Preferences │ Read Concern │ Write Concern │ Collation │
79 ├─────────────────┼──────────────┼───────────────┼───────────┤
80 │read_prefs │ opts │ opts │ opts │
81 ├─────────────────┼──────────────┼───────────────┼───────────┤
82 │Transaction │ Transaction │ Transaction │ │
83 ├─────────────────┼──────────────┼───────────────┼───────────┤
84 │database │ database │ database │ │
85 └─────────────────┴──────────────┴───────────────┴───────────┘
86 See the example for transactions and for the "distinct" command with
88 opts.
89 This function is considered a retryable read operation unless the pipe‐
91 line contains a write stage like $out or $merge. Upon a transient
92 error (a network error, errors due to replica set failover, etc.) the
93 operation is safely retried once. If retryreads is false in the URI
94 (see mongoc_uri_t) the retry behavior does not apply.
95
97 This function returns a newly allocated mongoc_cursor_t that should be
98 freed with mongoc_cursor_destroy() when no longer in use. The returned
99 mongoc_cursor_t is never NULL; if the parameters are invalid, the
100 bson_error_t in the mongoc_cursor_t is filled out, and the mongoc_cur‐
101 sor_t is returned before the server is selected. The user must call
102 mongoc_cursor_next() on the returned mongoc_cursor_t to execute the
103 aggregation pipeline.
104 WARNING:
106 Failure to handle the result of this function is a programming
107 error.
108
110 #include <bson/bson.h>
111 #include <mongoc/mongoc.h>
112 static mongoc_cursor_t *
114 current_op_query (mongoc_client_t *client)
115 {
116 mongoc_cursor_t *cursor;
117 mongoc_database_t *database;
118 bson_t *pipeline;
119 pipeline = BCON_NEW ("pipeline",
121 "[",
122 "{",
123 "$currentOp",
124 "{",
125 "}",
126 "}",
127 "]");
128 /* $currentOp must be run on the admin database */
130 database = mongoc_client_get_database (client, "admin");
131 cursor = mongoc_database_aggregate (
133 database, pipeline, NULL, NULL);
134 bson_destroy (pipeline);
136 mongoc_database_destroy (database);
137 return cursor;
139 }
140
142 MongoDB, Inc
143
145 2017-present, MongoDB, Inc
1461.16.2 Feb 25, 2020 MONGOC_DATABASE_AGGREGATE(3)