Examples of com.mongodb.DBCursor

com.mongodb.DBCursor
An iterator over database results. Doing a find() query on a collection returns a DBCursor thus
```
 DBCursor cursor = collection.find( query ); if( cursor.hasNext() ) DBObject obj = cursor.next(); 
```
Warning: Calling toArray or length on a DBCursor will irrevocably turn it into an array. This means that, if the cursor was iterating over ten million results (which it was lazily fetching from the database), suddenly there will be a ten-million element array in memory. Before converting to an array, make sure that there are a reasonable number of results using skip() and limit().
For example, to get an array of the 1000-1100th elements of a cursor, use
```
 List obj = collection.find( query ).skip( 1000 ).limit( 100 ).toArray(); 
```
@dochub cursors

                if (input.containsKey("$select")) {
                    select = buildDBObject((MongoRecord)input.get("$select"));
                    input.remove("$select");
                }
                DBObject object = buildDBObject(input);
                DBCursor cursor = collection.find(object, select);
                if (sort != null) {
                    cursor.sort(sort);
                }
                try {
                    if (mongoSpec.getSkip() > 0) {
                        cursor.skip(mongoSpec.getSkip());
                    }
                    if (mongoSpec.getLimit() != 0) {
                        cursor.limit(mongoSpec.getLimit());
                    }
                    if (mongoSpec.getBatchSize() != 0) {
                        cursor.batchSize(mongoSpec.getBatchSize());
                    }
                    if (!cursor.hasNext()) {
                        return null;
                    }
                    MongoListRecord results = new MongoListRecord();
                    while (cursor.hasNext()) {
                        DBObject result = cursor.next();
                        results.add(buildRecordFromDBObject(result));
                    }
                    return results;
                } finally {
                    cursor.close();
                }


            } else {
                throw new ResourceException("Invalid operation: " + operation);                
            }

View Full Code Here

    }
  }


  private ClosableIterator<Tuple> doFind(MongoDBQueryDescriptor query, QueryParameters queryParameters, DBCollection collection,
      EntityKeyMetadata entityKeyMetadata) {
    DBCursor cursor = collection.find( query.getCriteria(), query.getProjection() );


    if ( query.getOrderBy() != null ) {
      cursor.sort( query.getOrderBy() );
    }


    // apply firstRow/maxRows if present
    if ( queryParameters.getRowSelection().getFirstRow() != null ) {
      cursor.skip( queryParameters.getRowSelection().getFirstRow() );
    }


    if ( queryParameters.getRowSelection().getMaxRows() != null ) {
      cursor.limit( queryParameters.getRowSelection().getMaxRows() );
    }


    return new MongoDBResultsCursor( cursor, entityKeyMetadata );
  }

View Full Code Here

        queryBuilder.and("_id").greaterThan(parent + "/");
        queryBuilder.and("_id").lessThanEquals(parent + "0");
        DBObject query = queryBuilder.get();
        BasicDBObject keys = new BasicDBObject();
        keys.put("_id", 1);
        DBCursor cursor = nodes.find(query, keys);
        int count = 0;
        log("Query plan: " + cursor.explain());
        long time = System.currentTimeMillis();
        while (cursor.hasNext()) {
            DBObject obj = cursor.next();
            // dummy read operation (to ensure we did get the data)
            obj.get("_id");
            count++;
            // log(" read " + obj);
        }

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            queryBuilder.greaterThanEquals(startValue);
        }
        DBObject query = queryBuilder.get();
        long start = start();
        try {
            DBCursor cursor = dbCollection.find(query).sort(BY_ID_ASC);
            List<T> list = new ArrayList<T>();
            for (int i = 0; i < limit && cursor.hasNext(); i++) {
                DBObject o = cursor.next();
                T doc = convertFromDBObject(collection, o);
                if (collection == Collection.NODES && doc != null) {
                    doc.seal();
                    String id = doc.getId();
                    Lock lock = getAndLock(id);

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            // Fetch only the lastRev map and id
            final BasicDBObject keys = new BasicDBObject(Document.ID, 1);
            keys.put(Document.MOD_COUNT, 1);


            // Fetch lastRev for each such node
            DBCursor cursor = nodes.find(query.get(), keys);
            result.queryCount++;


            for (DBObject obj : cursor) {
                result.cacheEntriesProcessedCount++;
                String id = (String) obj.get(Document.ID);

View Full Code Here


                    QueryBuilder query = QueryBuilder.start(Document.ID)
                            .in(sameLevelNodes.keySet());


                    // Fetch lastRev and modCount for each such nodes
                    DBCursor cursor = nodes.find(query.get(), keys);
                    LOG.debug(
                            "Checking for changed nodes at level {} with {} paths",
                            tn.level(), sameLevelNodes.size());
                    result.queryCount++;
                    for (DBObject obj : cursor) {

View Full Code Here

        QueryBuilder builder = new QueryBuilder();
        if (maxLastModifiedTime != 0 && maxLastModifiedTime != -1) {
            builder.and(MongoBlob.KEY_LAST_MOD).lessThanEquals(maxLastModifiedTime);
        }


        final DBCursor cur =
                collection.find(builder.get(), fields).hint(fields)
                        .addOption(Bytes.QUERYOPTION_SLAVEOK);


        return new AbstractIterator<String>() {
            protected String computeNext() {
                if (cur.hasNext()) {
                    MongoBlob blob = (MongoBlob) cur.next();
                    if (blob != null) {
                        return blob.getId();
                    }
                }
                return endOfData();

View Full Code Here

     *            the name of the collection
     * @return a table definition for mongo db.
     */
    public static SimpleTableDef detectTable(DB db, String collectionName) {
        final DBCollection collection = db.getCollection(collectionName);
        final DBCursor cursor = collection.find().limit(1000);


        final SortedMap<String, Set<Class<?>>> columnsAndTypes = new TreeMap<String, Set<Class<?>>>();
        while (cursor.hasNext()) {
            DBObject object = cursor.next();
            Set<String> keysInObject = object.keySet();
            for (String key : keysInObject) {
                Set<Class<?>> types = columnsAndTypes.get(key);
                if (types == null) {
                    types = new HashSet<Class<?>>();
                    columnsAndTypes.put(key, types);
                }
                Object value = object.get(key);
                if (value != null) {
                    types.add(value.getClass());
                }
            }
        }
        cursor.close();


        final String[] columnNames = new String[columnsAndTypes.size()];
        final ColumnType[] columnTypes = new ColumnType[columnsAndTypes.size()];


        int i = 0;

View Full Code Here

        final DBCollection collection = _mongoDb.getCollection(table.getName());


        final DBObject query = createMongoDbQuery(table, whereItems);


        logger.info("Executing MongoDB 'find' query: {}", query);
        DBCursor cursor = collection.find(query);


        if (maxRows > 0) {
            cursor = cursor.limit(maxRows);
        }
        if (firstRow > 1) {
            final int skip = firstRow - 1;
            cursor = cursor.skip(skip);
        }


        return new MongoDbDataSet(cursor, columns, queryPostProcessed);
    }

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        range.getTargetID()).append("logId", range.getLogID());
    if (high > 0) {
      filter.append("id", new BasicDBObject("$lte", high));
    }


    DBCursor cursor = collection.find(filter);
    cursor.sort(new BasicDBObject("id", 1));


    List<LogEvent> logevents = new ArrayList<LogEvent>();
    while (cursor.hasNext()) {
      DBObject event = cursor.next();
      String targetId = (String) event.get("targetId");
      long logId = (Long) event.get("logId");
      long id = (Long) event.get("id");
      long time = (Long) event.get("time");
      int type = (Integer) event.get("type");

View Full Code Here

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