Lambda where fails but string where works

Question

Using the old MongoDB driver, I was able to perform the following query:

Query.Where("this.plan.sstats.used < this.plan.sstats.available")

But with the new one, I'm forced to write this:

builder.Filter
      .Where(t => t.Plan.StorageStats.UploadUsed < t.Plan.StorageStats.UploadAvailable)

These look the same, but the new one does not work and I receive this error message:

Additional information: Unsupported filter: ({plan.sstats.used} < {plan.sstats.available}).

The back-end version is currently the same, so I don't see any reason why this shouldn't continue to be able to work.

How do I fix this? Is there a better way of doing this, whilst maintaining atomicity?

@Liam New is 2.4, previous was 1.something. I'm not at work anymore so I can't check. — ProgrammingLlama
– ProgrammingLlama, Commented Jan 11, 2017 at 10:40

marc_s · Accepted Answer · 2017-02-01 19:50:43Z

2

Seems MongoDb drive doesn't support it any more. Me personally see two possible solutions:

1) You query bson, not your objects, that should work (i have tried with my sample data out):

FilterDefinition<BsonDocument> filter = 
    new BsonDocument("$where", "this.plan.sstats.used<this.plan.sstats.available");

Waht is bad on this approach: your should query your collection as BsonDocument collection.

2) You query your collection as ToEnumerable() and than just add your filter as Where linq statement. That will work too, but you loose querying data directly on mongodb.

3) You could use aggregation framework, i did it this way:

var result = collection.Aggregate()
        .Group(r => r.Plan.StorageStats.UploadUsed - r.Plan.StorageStats.UploadAvailable,
              r => new {r.Key, Plans= r.Select(t=>t.Plan)} )
        .Match(r=>r.Key < 0)
        .ToEnumerable()
        .SelectMany(r=>r.Plans);

Negative on aggregate is that you couldn't combine it with your other Filters you use in Find() call.

edited Feb 1, 2017 at 19:50

marc_s

760k186 gold badges1.4k silver badges1.5k bronze badges

answered Jan 11, 2017 at 9:56

Maksim Simkin

9,7084 gold badges38 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

ProgrammingLlama Over a year ago

Maksim, thanks for your reply. Unfortunately, we've been using it to do an atomic update, whilst ensuring that certain conditions are met, so this approach won't work.

Maksim Simkin Over a year ago

@john you still could work directly with bson (solution 1) , otherwise you will have to split your query and first read all id's that you need to update and than build contains filter.

ProgrammingLlama Over a year ago

That's what I was hoping to avoid :) Thank you for your help.

ProgrammingLlama · Accepted Answer · 2017-01-12 00:28:10Z

2

So, I'd also asked over on Mongo's JIRA and was given this as a potential alternative. I'm posting it here in case anyone is dissatisfied with Maksim's answer.

It's possible to create just a filter definition:

FilterDefinition<C> filter = new JsonFilterDefinition<C>("{ $where : \"this.plan.sstats.used < this.plan.sstats.available\" }");

Since strings can be converted to FilterDefinitions you could also write either of the following which both end up creating a JsonFilterDefinition: var filter = (FilterDefinition<C>)"{ $where : \"this.plan.sstats.used < this.plan.sstats.available\" }";

// or using an implicit conversion

FilterDefinition<C> filter = "{ $where : \"this.plan.sstats.used < this.plan.sstats.available\" }";

answered Jan 12, 2017 at 0:28

ProgrammingLlama

39.3k7 gold badges78 silver badges104 bronze badges

1 Comment

Maksim Simkin Over a year ago

cool, it works? you doing plain json filter and getting your Plans objects back?

Collectives™ on Stack Overflow

Lambda where fails but string where works

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related