Question

I have a necessity to remove all data from mongo collection. Droping of collection works faster than collection.remove(new BasicDBObject()). But it also removes index definitions. Therefore I want to restore index definitions after collection dropping.

In general I have following plan:

1. Get all index definitions before dropping:
   http://www.mongodb.org/display/DOCS/Java+Tutorial#JavaTutorial-GettingaListofIndexesonaCollection
2. Recreate definitions after dropping: http://www.mongodb.org/display/DOCS/Java+Tutorial#JavaTutorial-CreatingAnIndex

The issue for me is exact value that should be retrieved/passed for index recreation. E.g. will following correct work for all types of indexes:

List<DBObject> storedDefinitions = coll.getIndexInfo();
coll.drop();
for (DBObject storedDefinition : storedDefinitions) {
  coll.createIndex(storedDefinition.get("key"));
}

If no – what is the best way to achieve my goals?

Thanks for any help!

Answer 1

You’re close. You will need to read the index options of the retrieved indexes and apply those to the newly created index using the createIndex(DBObject key, DBObject options) version of the method.