mirror of
https://github.com/mongodb/mongo.git
synced 2024-12-01 09:32:32 +01:00
39 lines
1.0 KiB
C++
39 lines
1.0 KiB
C++
/* example of using a tailable cursor */
|
|
|
|
#include "../../client/dbclient.h"
|
|
#include "../../util/goodies.h"
|
|
|
|
using namespace mongo;
|
|
|
|
void foo() { }
|
|
|
|
/* "tail" the specified namespace, outputting elements as they are added.
|
|
_id values must be inserted in increasing order for this to work. (Some other
|
|
field could also be used.)
|
|
|
|
Note: one could use a capped collection and $natural order to do something
|
|
similar, using sort({$natural:1}), and then not need to worry about
|
|
_id's being in order.
|
|
*/
|
|
void tail(DBClientBase& conn, const char *ns) {
|
|
conn.ensureIndex(ns, fromjson("{_id:1}"));
|
|
BSONElement lastId;
|
|
Query query = Query().sort("_id");
|
|
while( 1 ) {
|
|
auto_ptr<DBClientCursor> c = conn.query(ns, query, 0, 0, 0, Option_CursorTailable);
|
|
while( 1 ) {
|
|
if( !c->more() ) {
|
|
if( c->isDead() ) {
|
|
// we need to requery
|
|
break;
|
|
}
|
|
sleepsecs(1);
|
|
}
|
|
BSONObj o = c->next();
|
|
lastId = o["_id"];
|
|
cout << o.toString() << endl;
|
|
}
|
|
query = QUERY( "_id" << GT << lastId ).sort("_id");
|
|
}
|
|
}
|