Unable to Call DOCUMENTID(root) from LINQ provider

[Matthewsre]

Unable to select the results from DOCUMENTID()

This is a valid SQL query that can be run against CosmosDB:

SELECT DOCUMENTID(c) FROM c

When trying to match up the projection with an example like this it fails as unsupported:

var projection = query.Select(r => DOCUMENTID(r));

This is mapped up and used in the tests:

azure-cosmos-dotnet-v3/Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/SqlObjects/SqlObjectVisitorBaselineTests.cs

Line 737 in c8935ac

SqlFunctionCallScalarExpression.Names.Documentid,

But is failing as not implemented:

   at Microsoft.Azure.Cosmos.Linq.BuiltinFunctionVisitor.VisitBuiltinFunctionCall(MethodCallExpression methodCallExpression, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitNonSubqueryScalarExpression(Expression expression, ReadOnlyCollection`1 parameters, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitScalarExpression(Expression expression, ReadOnlyCollection`1 parameters, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.CreateInitializers(ReadOnlyCollection`1 arguments, ReadOnlyCollection`1 members, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitNew(NewExpression inputExpression, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitNonSubqueryScalarExpression(Expression expression, ReadOnlyCollection`1 parameters, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitScalarExpression(Expression expression, ReadOnlyCollection`1 parameters, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitSelect(ReadOnlyCollection`1 arguments, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitMethodCall(MethodCallExpression inputExpression, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.Translate(Expression inputExpression, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.TranslateQuery(Expression inputExpression, IDictionary`2 parameters, CosmosLinqSerializerOptions linqSerializerOptions)
   at Microsoft.Azure.Cosmos.Linq.SqlTranslator.TranslateQuery(Expression inputExpression, CosmosLinqSerializerOptions linqSerializerOptions, IDictionary`2 parameters)
   at Microsoft.Azure.Cosmos.Linq.CosmosLinqQuery`1.ToQueryDefinition(IDictionary`2 parameters)
   at Microsoft.Azure.Cosmos.Linq.CosmosLinqExtensions.ToQueryDefinition[T](IQueryable`1 query)

I have also tried this approach with no success:

var projection = query.Select(r => r.DocumentId());

Here is the result:

   {{
	  "code": "",
	  "message": "Method 'DocumentId' is not supported., Windows/10.0.19043 cosmos-netstandard-sdk/3.17.1"
	}}
   
   Method 'DocumentId' is not supported., Windows/10.0.19043 cosmos-netstandard-sdk/3.17.1
   
   at Microsoft.Azure.Cosmos.Linq.BuiltinFunctionVisitor.VisitBuiltinFunctionCall(MethodCallExpression methodCallExpression, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitNonSubqueryScalarExpression(Expression expression, ReadOnlyCollection`1 parameters, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitScalarExpression(Expression expression, ReadOnlyCollection`1 parameters, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitSelect(ReadOnlyCollection`1 arguments, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.VisitMethodCall(MethodCallExpression inputExpression, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.Translate(Expression inputExpression, TranslationContext context)
   at Microsoft.Azure.Cosmos.Linq.ExpressionToSql.TranslateQuery(Expression inputExpression, IDictionary`2 parameters, CosmosLinqSerializerOptions linqSerializerOptions)
   at Microsoft.Azure.Cosmos.Linq.SqlTranslator.TranslateQuery(Expression inputExpression, CosmosLinqSerializerOptions linqSerializerOptions, IDictionary`2 parameters)
   at Microsoft.Azure.Cosmos.Linq.CosmosLinqQuery`1.ToQueryDefinition(IDictionary`2 parameters)
   at Microsoft.Azure.Cosmos.Linq.CosmosLinqExtensions.ToQueryDefinition[T](IQueryable`1 query)

[j82w]

I'm not a LINQ expert, but from what I can tell this isn't supported in LINQ currently. There is no extension methods exposing the functionality. I couldn't find any tests actually validating the DOCUMENTID being used in a e2e linq test. The test you pointed out is only unit testing a specific part of the LINQ logic.

[j82w]

@timsander1 please correct me if I'm wrong and this is a bug.