MongoDB.QueryHelper

Thanks for installing MongoDB.QueryHelper.

Michael (@mkennedy)

See this document and more at the GitHub project: https://github.com/mikeckennedy/mongodb-query-helper-for-dotnet

====================================================== MongoDB query helper for .NET

This library makes working with LINQ to MongoDB queries easier from C#. Specificially it is for debugging and runtime inquiry of LINQ queries.

There are two basic use cases:

Explain a LINQ query (does it use an index for example?)
Convert a LINQ query to the JavaScript code run in MongoDB

Consider this LINQ query:

var query = from p in mongo.People where p.Age > 20 && p.Name.Length >= 2 orderby p.Age descending select p;

Calling

Console.WriteLine( query.ToMongoQueryText() );

Outputs the following text;

{ "Age" : { "$gt" : 20 }, "Name" : /^.{2,}$/s }

Next, calling explain on query will return a strongly-typed QueryPlan object.

QueryPlan plan = query.ExplainTyped();

To see the output either work with it's properties, e.g.

bool usesIndex = plan.CursorType == CursorType.BtreeCursor;

Or just ToString the plan to get:

{ "cursor": "BtreeCursor Age_1 reverse", "isMultiKey": false, "n": 3, "nscanned": 3, "nscannedObjectsAllPlans": 5, "nscannedAllPlans": 5, "nscannedObjects": 3, "scanAndOrder": false, "indexOnly": false, "nYields": 0, "nChunkSkips": 0, "millis": 0, "indexBounds": { "Age": [ [ "Infinity", 20 ] ] }, "server": "WIN-7S2IMPQ2TOE:27017", "allPlans": null, "oldPlan": null, "clusteredType": null, "millisShardTotal": 0, "millisShardAvg": 0, "numQueries": 0, "numShards": 0, "filterSet": false, "stats": { "type": "FETCH", "works": 5, "yields": 0, "unyields": 0, "invalidates": 0, "advanced": 3, "needTime": false, "needFetch": false, "isEOF": true, "docsTested": 0, "children": [ { "type": "IXSCAN", "works": 3, "yields": 0, "unyields": 0, "invalidates": 0, "advanced": 3, "needTime": false, "needFetch": false, "isEOF": true, "docsTested": 0, "children": [], "keyPattern": "{ Age: 1 }", "boundsVerbose": "field #0['Age']: [1.#INF, 20)", "isMultiKey": 0, "yieldMovedCursor": 0, "dupsTested": 0, "dupsDropped": 0, "seenInvalidated": 0, "matchTested": 0, "keysExamined": 3 } ], "alreadyHasObj": 0, "forcedFetches": 0, "matchTested": 3 } }