Ordering by a property that belongs to a base class

Dear Mauricio,

First, thank you very much for your wonderful project. I’m using LiteDB 4.1 and encountered a problem when running an order by query.

I have a class Rect that derives from a class Shape, and I’m inserting Rect instances to litedb. Now, I want to select all the rects from the db ordered by a property (“LastUpdated”) that exists in the parent Shape class and it doesn’t work (I get the items in random order…)

internal static List<T> AllEntriesOrderedByDescending<T>(this LiteCollection<T> collection, int limit)
{
    return collection.Find(Query.All("LastUpdated", Query.Descending), skip: 0, limit: limit).ToList();
}

Nothing is indexed and the property of LastUpdated is fetched correctly in a regular “select all” query. I’ll be happy for your help.

[mbdavid]

Hi @tabtile, thanks!! Did you have an index in LastUpdated column? Use query order must be over an index only (not over a field only).

Try do:

collection.EnsureIndex(x => x.LastUpdated);

Before run your Find

Another way to sort is use FindSort method, but it’s avaiable only in LiteEngine instance: You can use like this:

var docs = db.Engine.FindSort("mycol", Query.All(), "$.LastUpdated", Query.Descending);
    
var entities = docs.Select(x => x.Mapper.ToObject<T>(x)).ToList();

[tabtile]

Hey Mauricio,

You’ve just made my day 😃 It works! Thank you!