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56 lines
1.7 KiB
C++
56 lines
1.7 KiB
C++
// tail.cpp
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/* Copyright 2009 10gen Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* example of using a tailable cursor */
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#include "../../client/dbclient.h"
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#include "../../util/goodies.h"
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using namespace mongo;
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void foo() { }
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/* "tail" the specified namespace, outputting elements as they are added.
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_id values must be inserted in increasing order for this to work. (Some other
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field could also be used.)
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Note: one could use a capped collection and $natural order to do something
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similar, using sort({$natural:1}), and then not need to worry about
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_id's being in order.
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*/
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void tail(DBClientBase& conn, const char *ns) {
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conn.ensureIndex(ns, fromjson("{_id:1}"));
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BSONElement lastId;
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Query query = Query().sort("_id");
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while( 1 ) {
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auto_ptr<DBClientCursor> c = conn.query(ns, query, 0, 0, 0, Option_CursorTailable);
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while( 1 ) {
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if( !c->more() ) {
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if( c->isDead() ) {
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// we need to requery
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break;
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}
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sleepsecs(1);
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}
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BSONObj o = c->next();
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lastId = o["_id"];
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cout << o.toString() << endl;
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}
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query = QUERY( "_id" << GT << lastId ).sort("_id");
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}
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}
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