1MONGOC_SESSION_OPTS_SET_SNAPSHOT(3)libmongocMONGOC_SESSION_OPTS_SET_SNAPSHOT(3)
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NAME

6       mongoc_session_opts_set_snapshot - mongoc_session_opts_set_snapshot()
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SYNOPSIS

9          void
10          mongoc_session_opts_set_snapshot (mongoc_session_opt_t *opts,
11                                            bool snapshot);
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13       Configure  snapshot  reads  for  a session. If true (false by default),
14       each read operation in the session will be sent with a "snapshot" level
15       read  concern.  After  the first read operation ("find", "aggregate" or
16       "distinct"), subsequent read operations will read from the  same  point
17       in  time  as  the  first read operation. Set to true to enable snapshot
18       reads. See the official documentation for Read Concern "snapshot".
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20       Snapshot reads and causal consistency are mutually exclusive.  Attempt‐
21       ing   to   set   both   to   true   will   result   in  an  error.  See
22       mongoc_session_opts_set_causal_consistency().
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24       Snapshot reads can only be used on MongoDB server version 5.0 and later
25       and  cannot  be used during a transaction. A write operation in a snap‐
26       shot-enabled session will also result in an error.
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PARAMETERS

29       • opts: A mongoc_session_opt_t.
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31       • snapshot: True or false.
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EXAMPLE

34          mongoc_client_t *client;
35          mongoc_session_opt_t *session_opts;
36          mongoc_client_session_t *client_session;
37          mongoc_collection_t *collection;
38          bson_t query_opts = BSON_INITIALIZER;
39          bson_t filter = BSON_INITIALIZER;
40          bson_t pipeline = BSON_INITIALIZER;
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42          client = mongoc_client_new ("mongodb://example/?appname=session-opts-example");
43          mongoc_client_set_error_api (client, MONGOC_ERROR_API_VERSION_2);
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45          session_opts = mongoc_session_opts_new ();
46          mongoc_session_opts_set_snapshot (session_opts, true);
47          client_session = mongoc_client_start_session (client, session_opts, &error);
48          mongoc_session_opts_destroy (session_opts);
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50          if (!client_session) {
51             fprintf (stderr, "Failed to start session: %s\n", error.message);
52             abort ();
53          }
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55          collection = mongoc_client_get_collection (client, "test", "collection");
56          r = mongoc_client_session_append (client_session, &find_opts, &error);
57          if (!r) {
58             fprintf (stderr, "mongoc_client_session_append failed: %s\n", error.message);
59             abort ();
60          }
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62          /* First read operation will set the snapshot time for subsequent reads. */
63          cursor = mongoc_collection_find_with_opts (collection, filter, &query_opts, NULL);
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65          /* Subsequent read operations will automatically read from the same point
66           * in time as the first read operation. */
67          cursor = mongoc_collection_aggregate (collection, MONGOC_QUERY_NONE, pipeline, &query_opts, NULL);
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AUTHOR

70       MongoDB, Inc
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73       2017-present, MongoDB, Inc
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781.23.1                           Oct 20, 202M2ONGOC_SESSION_OPTS_SET_SNAPSHOT(3)
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