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  1. Core Server
  2. SERVER-4815

Creating a unique index should have an ignore null values option

    • Type: Icon: New Feature New Feature
    • Resolution: Unresolved
    • Priority: Icon: Major - P3 Major - P3
    • None
    • Affects Version/s: 2.0.2
    • Component/s: Index Maintenance
    • Query Optimization

      I've seen Issue 2028 (https://jira.mongodb.org/browse/SERVER-2028) and I don't think a sparse index is a good enough solution. One of the reasons I think a sparse index fails as a solution is because when the index is used in a lookup, the documents that do have null values in the indexed field are ignored in search results. Let me give a concrete example of what I think the behavior should be...

      Let's say I'm adding a new property to a "users" collection. The new property is an api token, and needs to be unique across the entire collection. I'd like to be able to do db.users.ensureIndex(

      {"token": 1, "unique": true}

      ), but this will of course fail b/c mongo will hit more than one null value. On the other hand, a sparse index here doesn't work because when I try to do a read query on that column where that column would get used (db.users.find({token: {"$ne": null}}).count) the result set excludes all the users b/c it's a new property.

            Assignee:
            backlog-query-optimization [DO NOT USE] Backlog - Query Optimization
            Reporter:
            ajsharp Alex Sharp
            Votes:
            6 Vote for this issue
            Watchers:
            9 Start watching this issue

              Created:
              Updated: