CSHARP-4248: Allow collectionless $lookup with $documents. #1544
Conversation
| /// <notes>The Results property of <see cref="T:LookupResult{TSource,TDocument}"/> contains the matching foreign documents.</notes> | ||
| public static IQueryable<LookupResult<TSource, TDocument>> Lookup<TSource, TDocument, TField>( | ||
| this IQueryable<TSource> source, | ||
| Expression<Func<TSource, IEnumerable<TDocument>>> documents, |
There was a problem hiding this comment.
documents could also be a constant but the server allows the documents to be computed.
| /// <typeparam name="TField">The type of the fields being compared.</typeparam> | ||
| /// <returns>An <see cref="T:IQueryable{LookupResult{TSource,TForeign}}"/> with the results of the Lookup.</returns> | ||
| /// <notes>The Results property of <see cref="T:LookupResult{TSource,TForeign}"/> contains the matching foreign documents.</notes> | ||
| public static IQueryable<LookupResult<TSource, TForeign>> Lookup<TSource, TForeign, TField>( |
There was a problem hiding this comment.
These 6 new overloads correspond to the 6 variations of $lookup supported by the server:
1: from with localField and foreignField
2. from with pipeline
3. from with localField and foreignField and pipeline (the "concise" syntax)
4. $documents with localField and foreignField
5. $documents with pipeline
6. $documents with localField and foreignField and pipeline (the "concise" syntax)
| AstProject.Exclude("_id")); | ||
| var wrappedLocalSerializer = WrappedValueSerializer.Create("_local", localSerializer); | ||
|
|
||
| IMongoCollection foreignCollection = null; |
There was a problem hiding this comment.
The technique here is to optionally construct the pieces that make up the lookup and then build the AST at the end.
Not all pieces are present in all overloads of Lookup.
|
|
||
| AstStage lookupStage = null; | ||
| IBsonSerializer resultSerializer = null; | ||
| if (method.Is(MongoQueryableMethod.LookupWithFromAndLocalFieldAndForeignField)) |
There was a problem hiding this comment.
Here is where we start building the 6 variations of AST using the pieces that were created above.
| context = context.WithSymbol(localSymbol); | ||
|
|
||
| var provider = new MongoQueryProvider<TDocument>(documentSerializer, session: null, options: null); | ||
| var queryable = new MongoQuery<TDocument, TDocument>(provider); |
There was a problem hiding this comment.
This is a new way of creating an IQueryable that is not tied to any particular collection.
Most of the time an IQueryable is tied to a collection being queried (or possibly a database for some kinds of queries).
| /// <typeparam name="TLocal">The type of the local documents.</typeparam> | ||
| /// <typeparam name="TResult">The type of the result values.</typeparam> | ||
| [BsonSerializer(typeof(LookupResultSerializer<,>))] | ||
| public struct LookupResult<TLocal, TResult> |
There was a problem hiding this comment.
Class that is the result of a Lookup.
| /// <summary> | ||
| /// The result values. | ||
| /// </summary> | ||
| public TResult[] Results { get; init; } |
There was a problem hiding this comment.
The results are either the TForeign documents or if a pipeline is provided then the TResult of the pipeline.
| _pipelineInputSerializer = NoPipelineInputSerializer.Instance; | ||
| } | ||
|
|
||
| internal MongoQueryProvider( |
There was a problem hiding this comment.
New constructor to support LINQ queries that aren't tied to any collection or database.
| @@ -23,6 +23,13 @@ | |||
|
|
|||
| namespace MongoDB.Driver | |||
| { | |||
| internal interface IMongoCollection | |||
There was a problem hiding this comment.
Ideally IMongoCollection<TDocument> would derive from IMongoColletion but that could be considered a breaking change.
There was a problem hiding this comment.
Yep, it is. Could you please add this to the TODO list for next major release? https://docs.google.com/document/d/1pGrELOhAvzXvavUDqIA-su0ic6wf2Mu6h20llrYj_VA
| @@ -31,7 +31,7 @@ | |||
|
|
|||
| namespace MongoDB.Driver | |||
| { | |||
| internal sealed class MongoCollectionImpl<TDocument> : MongoCollectionBase<TDocument> | |||
| internal sealed class MongoCollectionImpl<TDocument> : MongoCollectionBase<TDocument>, IMongoCollection | |||
There was a problem hiding this comment.
Since IMongoCollection<TDocument> does not derive from IMongoCollection we have to list IMongoCollection here as an interface we implement.
| @@ -23,6 +23,13 @@ | |||
|
|
|||
| namespace MongoDB.Driver | |||
| { | |||
| internal interface IMongoCollection | |||
There was a problem hiding this comment.
Yep, it is. Could you please add this to the TODO list for next major release? https://docs.google.com/document/d/1pGrELOhAvzXvavUDqIA-su0ic6wf2Mu6h20llrYj_VA
| Ensure.IsNotNull(localField, nameof(localField)); | ||
| Ensure.IsNotNull(foreignField, nameof(foreignField)); | ||
|
|
||
| return source.Provider.CreateQuery<LookupResult<TSource, TForeign>>( |
There was a problem hiding this comment.
Should it be source.GetMongoQueryProvider() instead to validate the provider is IMongoQueryProvider?
No description provided.