1MONGOC_COLLECTION_AGGREGATE(3) MongoDB C Driver MONGOC_COLLECTION_AGGREGATE(3)
2
6 mongoc_collection_aggregate - mongoc_collection_aggregate()
7
9 mongoc_cursor_t *
10 mongoc_collection_aggregate (mongoc_collection_t *collection,
11 mongoc_query_flags_t flags,
12 const bson_t *pipeline,
13 const bson_t *opts,
14 const mongoc_read_prefs_t *read_prefs)
15 BSON_GNUC_WARN_UNUSED_RESULT;
16
18 · collection: A mongoc_collection_t.
19 · flags: A mongoc_query_flags_t.
21 · pipeline: A bson_t, either a BSON array or a BSON document containing
23 an array field named "pipeline".
24 · opts: A bson_t containing options for the command, or NULL.
26 · read_prefs: A mongoc_read_prefs_t or NULL.
28 opts may be NULL or a BSON document with additional command options:
30 · readConcern: Construct a mongoc_read_concern_t and use mon‐
32 goc_read_concern_append to add the read concern to opts. See the
33 example code for mongoc_client_read_command_with_opts. Read concern
34 requires MongoDB 3.2 or later, otherwise an error is returned.
35 · writeConcern: For aggregations that include "$out", you can construct
37 a mongoc_write_concern_t and use mongoc_write_concern_append to add
38 the write concern to opts. See the example code for mon‐
39 goc_client_write_command_with_opts.
40 · sessionId: Construct a mongoc_client_session_t with mon‐
42 goc_client_start_session and use mongoc_client_session_append to add
43 the session to opts. See the example code for mongoc_client_ses‐
44 sion_t.
45 · bypassDocumentValidation: Set to true to skip server-side schema val‐
47 idation of the provided BSON documents.
48 · collation: Configure textual comparisons. See Setting Collation
50 Order, and the MongoDB Manual entry on Collation. Collation requires
51 MongoDB 3.2 or later, otherwise an error is returned.
52 · serverId: To target a specific server, include an int32 "serverId"
54 field. Obtain the id by calling mongoc_client_select_server, then
55 mongoc_server_description_id on its return value.
56 · batchSize: To specify the number of documents to return in each batch
58 of a response from the server, include an int "batchSize" field.
59 For a list of all options, see the MongoDB Manual entry on the aggre‐
61 gate command.
62
64 This function shall execute an aggregation query on the underlying col‐
65 lection. For more information on building aggregation pipelines, see
66 the MongoDB Manual entry on the aggregate command.
67 Read preferences, read and write concern, and collation can be overrid‐
69 den by various sources. The highest-priority sources for these options
70 are listed first in the following table. In a transaction, read concern
71 and write concern are prohibited in opts and the read preference must
72 be primary or NULL. Write concern is applied from opts, or if opts has
73 no write concern and the aggregation pipeline includes "$out", the
74 write concern is applied from collection. The write concern is omitted
75 for MongoDB before 3.4.
76 ┌─────────────────┬──────────────┬───────────────┬───────────┐
78 │Read Preferences │ Read Concern │ Write Concern │ Collation │
79 ├─────────────────┼──────────────┼───────────────┼───────────┤
80 │read_prefs │ opts │ opts │ opts │
81 ├─────────────────┼──────────────┼───────────────┼───────────┤
82 │Transaction │ Transaction │ Transaction │ │
83 ├─────────────────┼──────────────┼───────────────┼───────────┤
84 │collection │ collection │ collection │ │
85 └─────────────────┴──────────────┴───────────────┴───────────┘
86 See the example for transactions and for the "distinct" command with
88 opts.
89
91 This function returns a newly allocated mongoc_cursor_t that should be
92 freed with mongoc_cursor_destroy() when no longer in use. The returned
93 mongoc_cursor_t is never NULL; if the parameters are invalid, the
94 bson_error_t in the mongoc_cursor_t is filled out, and the mongoc_cur‐
95 sor_t is returned before the server is selected.
96 WARNING:
98 Failure to handle the result of this function is a programming
99 error.
100
102 #include <bson/bson.h>
103 #include <mongoc/mongoc.h>
104 static mongoc_cursor_t *
106 pipeline_query (mongoc_collection_t *collection)
107 {
108 mongoc_cursor_t *cursor;
109 bson_t *pipeline;
110 pipeline = BCON_NEW ("pipeline",
112 "[",
113 "{",
114 "$match",
115 "{",
116 "foo",
117 BCON_UTF8 ("A"),
118 "}",
119 "}",
120 "{",
121 "$match",
122 "{",
123 "bar",
124 BCON_BOOL (false),
125 "}",
126 "}",
127 "]");
128 cursor = mongoc_collection_aggregate (
130 collection, MONGOC_QUERY_NONE, pipeline, NULL, NULL);
131 bson_destroy (pipeline);
133 return cursor;
135 }
136
138 When using $out, the pipeline stage that writes, the write_concern
139 field of the mongoc_cursor_t will be set to the mongoc_write_concern_t
140 parameter, if it is valid, and applied to the write command when mon‐
141 goc_cursor_next() is called. Pass any other parameters to the aggregate
142 command, besides pipeline, as fields in opts:
143 mongoc_write_concern_t *write_concern = mongoc_write_concern_new ();
145 mongoc_write_concern_set_w (write_concern, 3);
146 pipeline =
148 BCON_NEW ("pipeline", "[", "{", "$out", BCON_UTF8 ("collection2"), "}", "]");
149 opts = BCON_NEW ("bypassDocumentValidation", BCON_BOOL (true));
151 mongoc_write_concern_append (write_concern, opts);
152 cursor = mongoc_collection_aggregate (
154 collection1, MONGOC_QUERY_NONE, pipeline, opts, NULL);
155
157 MongoDB, Inc
158
160 2017-present, MongoDB, Inc
1611.13.1 Jan 24, 2019 MONGOC_COLLECTION_AGGREGATE(3)