SYNOPSIS
typedef struct _mongoc_cursor_t mongoc_cursor_t;
mongoc_cursor_t provides access to a MongoDB query cursor. It wraps up the wire protocol negotiation required to initiate a query and retrieve an unknown number of documents.
Cursors are lazy, meaning that no network traffic occurs until the first call to mongoc_cursor_next(3) \&.
At that point we can:
- \[bu]
- Determine which host we've connected to with mongoc_cursor_get_host(3) \&.
- \[bu]
- Retrieve more records with repeated calls to mongoc_cursor_next(3) \&.
- \[bu]
- Test for more records with mongoc_cursor_more(3)
- \[bu]
- Clone a query to repeat execution at a later point with mongoc_cursor_clone(3) \&.
- \[bu]
-
Test for errors with
mongoc_cursor_error(3)
\&.
THREAD SAFETY
mongoc_cursor_t is NOT thread safe. It may only be used from the thread it was created from.
EXAMPLE
/* gcc example.c -o example $(pkg-config --cflags --libs libmongoc-1.0) */
/* ./example-client [CONNECTION_STRING [COLLECTION_NAME]] */
#include <mongoc.h>
#include <stdio.h>
#include <stdlib.h>
int
main (int argc,
char *argv[])
{
mongoc_client_t *client;
mongoc_collection_t *collection;
mongoc_cursor_t *cursor;
bson_error_t error;
const bson_t *doc;
const char *uristr = "mongodb://127.0.0.1/";
const char *collection_name = "test";
bson_t query;
char *str;
mongoc_init ();
if (argc > 1) {
uristr = argv [1];
}
if (argc > 2) {
collection_name = argv [2];
}
client = mongoc_client_new (uristr);
if (!client) {
fprintf (stderr, "Failed to parse URI.\n");
return EXIT_FAILURE;
}
bson_init (&query);
#if 0
bson_append_utf8 (&query, "hello", -1, "world", -1);
#endif
collection = mongoc_client_get_collection (client, "test", collection_name);
cursor = mongoc_collection_find (collection,
MONGOC_QUERY_NONE,
0,
0,
0,
&query,
NULL, /* Fields, NULL for all. */
NULL); /* Read Prefs, NULL for default */
while (mongoc_cursor_next (cursor, &doc)) {
str = bson_as_json (doc, NULL);
fprintf (stdout, "%s\n", str);
bson_free (str);
}
if (mongoc_cursor_error (cursor, &error)) {
fprintf (stderr, "Cursor Failure: %s\n", error.message);
return EXIT_FAILURE;
}
bson_destroy (&query);
mongoc_cursor_destroy (cursor);
mongoc_collection_destroy (collection);
mongoc_client_destroy (client);
mongoc_cleanup ();
return EXIT_SUCCESS;
}