How does RavenDb "In" operator work?

Question

I probably don't understand how the "In" extension method in RavenDb works. I thought that it is an equivalent of the IN command in SQL world, e.g. WHERE Number IN (1, 2, 3). But it behaves quite weird.

// i have 3 records - two with Normal severity, one with Low severity
using (var session = store.OpenSession())
{
    session.Store(new TestObject { Name = "o1", Severity = Severity.Normal });
    session.Store(new TestObject { Name = "o2", Severity = Severity.Low });
    session.Store(new TestObject { Name = "o3", Severity = Severity.Normal });
    session.SaveChanges();
}

// this writes the Low severity record, it seems correct
using (var session = store.OpenSession())
{
    var data = session.Query<TestObject>()
        .Where(o => o.Severity.In(new[] { Severity.Low }))
        .OrderBy(o => o.Name).ToList();
    data.ForEach(r => Console.WriteLine(r));
}

// this writes also the Low severity record, it still seems correct
using (var session = store.OpenSession())
{
    var data = session.Query<TestObject>()
        .Where(o => o.Severity.In(new[] { Severity.Low, Severity.High }))
        .OrderBy(o => o.Name).ToList();
    data.ForEach(r => Console.WriteLine(r));
}

// this writes all records, still seems correct
using (var session = store.OpenSession())
{
    var data = session.Query<TestObject>()
        .Where(o => o.Severity.In(
            new[] { Severity.High, Severity.Low, Severity.Normal }))
        .OrderBy(o => o.Name).ToList();
    data.ForEach(r => Console.WriteLine(r));
}

// but this does not write anything 
// despite there are 2 records with Normal severity
using (var session = store.OpenSession())
{
    var data = session.Query<TestObject>()
        .Where(o => o.Severity.In(new[] { Severity.High, Severity.Normal }))
        .OrderBy(o => o.Name).ToList();
    data.ForEach(r => Console.WriteLine(r));
}

// and this does not write anything either, 
// I just tried whether the order of values in the array matters
using (var session = store.OpenSession())
{
    var data = session.Query<TestObject>()
        .Where(o => o.Severity.In(new[] { Severity.Normal, Severity.High }))
        .OrderBy(o => o.Name).ToList();
    data.ForEach(r => Console.WriteLine(r));
}

Or did I find a bug in the RavenDb/Lucene engine?

Edit

I have found another strange thing. It has to do something with the alphabetical order of enum members. When I rename the Severity.Normal to Severity.A, the last two queries behave correctly and return the results. When I rename the Severity.Normal to Severity.La, it still works (because La < Low). But when I rename the Severity.Normal to Severity.Lu (Lu > Low), it breaks and the last two queries are not returning results any more. The original sample does not work because Normal > Low. But I still wonder why it happens because it makes no sense to me.

Answer 1

You are running into stale indexes, which is why you get strange results. You need to wait for the indexing to complete first.