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CSHARP-5396: Add support for arbitrary join inner expression arguments in LINQ #1531

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0f1793b
CSHARP-5396: Fix LINQ join error when add .Where to foreign collectio…
kerem-acerNov 4, 2024
19d088b
Add support for arbitrary inner expression arguments
kerem-acerNov 11, 2024
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Original file line numberDiff line numberDiff line change
Expand Up@@ -36,20 +36,32 @@ public static object Evaluate(this Expression expression)
}
}

public static (string CollectionName, IBsonSerializer DocumentSerializer) GetCollectionInfo(this Expression innerExpression, Expression containerExpression)
public static (IMongoQueryProviderInternal QueryProvider, bool IsRawCollectionExpression) FindMongoQueryProvider(this Expression innerExpression, Expression containerExpression)
{
if (innerExpression is ConstantExpression constantExpression &&
constantExpression.Value is IQueryable queryable &&
queryable.Provider is IMongoQueryProviderInternal mongoQueryProvider &&
mongoQueryProvider.CollectionNamespace != null)
var mongoQueryProvider = ExtractQueryProviderFromExpression(innerExpression);
if (mongoQueryProvider.QueryProvider is not null)
{
return (mongoQueryProvider.CollectionNamespace.CollectionName, mongoQueryProvider.PipelineInputSerializer);
return mongoQueryProvider;
}

var message = $"inner expression must be a MongoDB IQueryable against a collection";
var message = "inner expression must be a MongoDB IQueryable against a collection";
throw new ExpressionNotSupportedException(innerExpression, containerExpression, because: message);
}

private static (IMongoQueryProviderInternal QueryProvider, bool IsRawCollectionExpression) ExtractQueryProviderFromExpression(Expression expression, int depth = 0)
{
return expression switch
{
MethodCallExpression methodCallExpression => ExtractQueryProviderFromExpression(methodCallExpression.Arguments.FirstOrDefault(), depth + 1),
ConstantExpression constantExpression => constantExpression.Value switch
{
IQueryable { Provider: IMongoQueryProviderInternal queryProvider } => (queryProvider, depth == 0),
_ => default
},
_ => default
};
}

public static TValue GetConstantValue<TValue>(this Expression expression, Expression containingExpression)
{
if (expression is ConstantExpression constantExpression)
Expand Down
Original file line numberDiff line numberDiff line change
Expand Up@@ -13,6 +13,8 @@
* limitations under the License.
*/

using System.Linq;
using System;
using System.Linq.Expressions;
using MongoDB.Bson.Serialization;
using MongoDB.Driver.Linq.Linq3Implementation.Ast;
Expand DownExpand Up@@ -63,15 +65,31 @@ public static AstPipeline Translate(TranslationContext context, MethodCallExpres
AstProject.Exclude("_id"));
var wrappedOuterSerializer = WrappedValueSerializer.Create("_outer", outerSerializer);

var (innerCollectionName, innerSerializer) = innerExpression.GetCollectionInfo(containerExpression: expression);
var (queryProvider, isRawCollectionExpression) = innerExpression.FindMongoQueryProvider(containerExpression: expression);
var localField = outerKeySelectorLambda.TranslateToDottedFieldName(context, wrappedOuterSerializer);
var foreignField = innerKeySelectorLambda.TranslateToDottedFieldName(context, innerSerializer);
var foreignField = innerKeySelectorLambda.TranslateToDottedFieldName(context, queryProvider.PipelineInputSerializer);

var lookupStage = AstStage.Lookup(
from: innerCollectionName,
localField,
foreignField,
@as: "_inner");
AstStage lookupStage;

if (isRawCollectionExpression)
{
lookupStage = AstStage.Lookup(
from: queryProvider.CollectionNamespace.CollectionName,
localField,
foreignField,
@as: "_inner");
}
else
{
var lookupPipeline = ExpressionToPipelineTranslator.Translate(context, innerExpression);
lookupStage = AstStage.Lookup(
from: queryProvider.CollectionNamespace.CollectionName,
localField,
foreignField,
Array.Empty<AstComputedField>(),
lookupPipeline,
@as: "_inner");
}

var unwindStage = AstStage.Unwind("_inner");

Expand All@@ -80,7 +98,7 @@ public static AstPipeline Translate(TranslationContext context, MethodCallExpres
var outerSymbol = context.CreateSymbol(outerParameter, outerField, outerSerializer);
var innerParameter = resultSelectorLambda.Parameters[1];
var innerField = AstExpression.GetField(AstExpression.RootVar, "_inner");
var innerSymbol = context.CreateSymbol(innerParameter, innerField, innerSerializer);
var innerSymbol = context.CreateSymbol(innerParameter, innerField, queryProvider.PipelineInputSerializer);
var resultSelectorContext = context.WithSymbols(outerSymbol, innerSymbol);
var resultSelectorTranslation = ExpressionToAggregationExpressionTranslator.Translate(resultSelectorContext, resultSelectorLambda.Body);
var (projectStage, projectSerializer) = ProjectionHelper.CreateProjectStage(resultSelectorTranslation);
Expand Down