@Test
@Ignore
public void manyChildNodes() {
DB db = MongoUtils.getConnection().getDB();
MongoUtils.dropCollections(db);
DBCollection nodes = db.getCollection(Collection.NODES.toString());
DBObject index = new BasicDBObject();
// modification time (descending)
index.put("_mod", -1L);
// and then id (ascending)
index.put("_id", 1L);
DBObject options = new BasicDBObject();
// options.put("unique", Boolean.TRUE);
nodes.ensureIndex(index, options);
// index on (_id, _mod):
// Query plan: { "cursor" : "BtreeCursor _id_1__mod_-1" ,
// "isMultiKey" : false , "n" : 2000 , "nscannedObjects" : 2000 ,
// "nscanned" : 954647 , "nscannedObjectsAllPlans" : 1907080 ,
// "nscannedAllPlans" : 2859727 , "scanAndOrder" : false ,
// "indexOnly" : true , "nYields" : 5 , "nChunkSkips" : 0 ,
// "millis" : 5112 ,...
// Time: 2229 ms
// Count: 2000
// index on (_mod, _id)
// Query plan: { "cursor" : "BtreeCursor _mod_-1__id_1" ,
// "isMultiKey" : false , "n" : 2000 , "nscannedObjects" : 2000 ,
// "nscanned" : 2000 , "nscannedObjectsAllPlans" : 2203 ,
// "nscannedAllPlans" : 2203 , "scanAndOrder" : false ,
// "indexOnly" : true , "nYields" : 0 , "nChunkSkips" : 0 ,
// "millis" : 3 ,...
// Time: 43 ms
// Count: 2000
int children = 1000000;
int perInsert = 1000;
int group = 0;
String parent = "/parent/node/abc";
for (int i = 0; i < children;) {
DBObject[] inserts = new DBObject[perInsert];
group++;
for (int j = 0; j < perInsert; j++, i++) {
BasicDBObject doc = new BasicDBObject();
inserts[j] = doc;
doc.put("_id", parent + "/node" + i);
doc.put("_mod", group);
}
nodes.insert(inserts, WriteConcern.SAFE);
log("inserted " + i + "/" + children);
}
QueryBuilder queryBuilder = QueryBuilder.start("_mod");
queryBuilder.greaterThanEquals(group - 1);
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();