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CSHARP-4443: Add comprehensive dictionary LINQ support for all 3 representations #1804

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b66daf1
CSHARP-4443: Add comprehensive dictionary LINQ support for all 3 repr…
adelinowona Oct 31, 2025
34f74ce
add tests and update/remove duplicated tests
adelinowona Oct 31, 2025
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28 changes: 27 additions & 1 deletion src/MongoDB.Bson/Serialization/Serializers/KeyValuePairSerializer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,22 @@ public interface IKeyValuePairSerializer
BsonType Representation { get; }
}

/// <summary>
/// An extended interface for KeyValuePairSerializer that provides access to key and value serializers.
/// </summary>
public interface IKeyValuePairSerializerV2 : IKeyValuePairSerializer
{
/// <summary>
/// Gets the key serializer.
/// </summary>
IBsonSerializer KeySerializer { get; }

/// <summary>
/// Gets the value serializer.
/// </summary>
IBsonSerializer ValueSerializer { get; }
}

/// <summary>
/// Static factory class for KeyValuePairSerializers.
/// </summary>
Expand Down Expand Up @@ -61,7 +77,7 @@ public static IBsonSerializer Create(
public sealed class KeyValuePairSerializer<TKey, TValue> :
StructSerializerBase<KeyValuePair<TKey, TValue>>,
IBsonDocumentSerializer,
IKeyValuePairSerializer
IKeyValuePairSerializerV2
{
// private constants
private static class Flags
Expand Down Expand Up @@ -191,6 +207,16 @@ public IBsonSerializer<TValue> ValueSerializer
get { return _lazyValueSerializer.Value; }
}

/// <summary>
/// Gets the key serializer.
/// </summary>
IBsonSerializer IKeyValuePairSerializerV2.KeySerializer => KeySerializer;

/// <summary>
/// Gets the value serializer.
/// </summary>
IBsonSerializer IKeyValuePairSerializerV2.ValueSerializer => ValueSerializer;

// public methods
/// <summary>
/// Deserializes a value.
Expand Down
5 changes: 5 additions & 0 deletions src/MongoDB.Driver/Linq/Linq3Implementation/Ast/Expressions/AstExpression.cs
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Expand Up @@ -134,6 +134,11 @@ public static AstExpression ArrayElemAt(AstExpression array, AstExpression index
return new AstBinaryExpression(AstBinaryOperator.ArrayElemAt, array, index);
}

public static AstExpression ArrayToObject(AstExpression arg)
{
return new AstUnaryExpression(AstUnaryOperator.ArrayToObject, arg);
}

public static AstExpression Avg(AstExpression array)
{
return new AstUnaryExpression(AstUnaryOperator.Avg, array);
Expand Down
165 changes: 160 additions & 5 deletions ...onToAggregationExpressionTranslators/MemberExpressionToAggregationExpressionTranslator.cs
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Expand Up @@ -14,7 +14,6 @@
*/

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
Expand Down Expand Up @@ -66,11 +65,21 @@ public static TranslatedExpression Translate(TranslationContext context, MemberE

if (!DocumentSerializerHelper.AreMembersRepresentedAsFields(containerTranslation.Serializer, out _))
{
if (member is PropertyInfo propertyInfo && propertyInfo.Name == "Length")
if (member is PropertyInfo propertyInfo && propertyInfo.Name == "Length")
{
return LengthPropertyToAggregationExpressionTranslator.Translate(context, expression);
}

if (TryTranslateDictionaryProperty(expression, containerTranslation, member, out var translatedDictionaryProperty))
{
return translatedDictionaryProperty;
}

if (TryTranslateKeyValuePairProperty(expression, containerTranslation, member, out var translatedKeyValuePairProperty))
{
return translatedKeyValuePairProperty;
}

if (TryTranslateCollectionCountProperty(expression, containerTranslation, member, out var translatedCount))
{
return translatedCount;
Expand Down Expand Up @@ -121,11 +130,20 @@ private static bool TryTranslateCollectionCountProperty(MemberExpression express
{
if (EnumerableProperty.IsCountProperty(expression))
{
SerializationHelper.EnsureRepresentationIsArray(expression, container.Serializer);
AstExpression ast;

var ast = AstExpression.Size(container.Ast);
var serializer = Int32Serializer.Instance;
if (container.Serializer is IBsonDictionarySerializer dictionarySerializer &&
dictionarySerializer.DictionaryRepresentation == DictionaryRepresentation.Document)
{
ast = AstExpression.Size(AstExpression.ObjectToArray(container.Ast));
}
else
{
SerializationHelper.EnsureRepresentationIsArray(expression, container.Serializer);
ast = AstExpression.Size(container.Ast);
}

var serializer = Int32Serializer.Instance;
result = new TranslatedExpression(expression, ast, serializer);
return true;
}
Expand Down Expand Up @@ -187,5 +205,142 @@ private static bool TryTranslateDateTimeProperty(MemberExpression expression, Tr

return false;
}

private static bool TryTranslateKeyValuePairProperty(MemberExpression expression, TranslatedExpression container, MemberInfo memberInfo, out TranslatedExpression result)
{
result = null;

if (container.Expression.Type.IsGenericType &&
container.Expression.Type.GetGenericTypeDefinition() == typeof(KeyValuePair<,>) &&
container.Serializer is IKeyValuePairSerializerV2 { Representation: BsonType.Array } kvpSerializer)
{
AstExpression ast;
IBsonSerializer serializer;

switch (memberInfo.Name)
{
case "Key":
ast = AstExpression.ArrayElemAt(container.Ast, 0);
serializer = kvpSerializer.KeySerializer;
break;
case "Value":
ast = AstExpression.ArrayElemAt(container.Ast, 1);
serializer = kvpSerializer.ValueSerializer;
break;
default:
throw new ExpressionNotSupportedException(expression);
}
result = new TranslatedExpression(expression, ast, serializer);
return true;
}

return false;
}

private static bool TryTranslateDictionaryProperty(MemberExpression expression, TranslatedExpression container, MemberInfo memberInfo, out TranslatedExpression result)
{
result = null;

if (memberInfo is PropertyInfo propertyInfo &&
propertyInfo.DeclaringType.IsGenericType &&
(propertyInfo.DeclaringType.GetGenericTypeDefinition() == typeof(Dictionary<,>) ||
propertyInfo.DeclaringType.GetGenericTypeDefinition() == typeof(IDictionary<,>)))
{
if (container.Serializer is IBsonDictionarySerializer dictionarySerializer)
{
switch (propertyInfo.Name)
{
case "Count":
{
AstExpression countAst;
switch (dictionarySerializer.DictionaryRepresentation)
{
case DictionaryRepresentation.Document:
countAst = AstExpression.Size(AstExpression.ObjectToArray(container.Ast));
break;
case DictionaryRepresentation.ArrayOfArrays:
case DictionaryRepresentation.ArrayOfDocuments:
countAst = AstExpression.Size(container.Ast);
break;
default:
throw new ExpressionNotSupportedException(expression);
}

var serializer = Int32Serializer.Instance;
result = new TranslatedExpression(expression, countAst, serializer);
return true;
}

case "Keys":
{
AstExpression keysAst;
switch (dictionarySerializer.DictionaryRepresentation)
{
case DictionaryRepresentation.Document:
keysAst = AstExpression.GetField(AstExpression.ObjectToArray(container.Ast), "k");
break;
case DictionaryRepresentation.ArrayOfArrays:
{
var kvp = AstExpression.Var("kvp");
keysAst = AstExpression.Map(
input: container.Ast,
@as: kvp,
@in: AstExpression.ArrayElemAt(kvp, 0));
break;
}
case DictionaryRepresentation.ArrayOfDocuments:
keysAst = AstExpression.GetField(container.Ast, "k");
break;

default:
throw new ExpressionNotSupportedException(expression);
}

var serializer = ArraySerializerHelper.CreateSerializer(dictionarySerializer.KeySerializer);
result = new TranslatedExpression(expression, keysAst, serializer);
return true;
}

case "Values":
{
AstExpression valuesAst;
switch (dictionarySerializer.DictionaryRepresentation)
{
case DictionaryRepresentation.Document:
valuesAst = AstExpression.GetField(AstExpression.ObjectToArray(container.Ast), "v");
break;
case DictionaryRepresentation.ArrayOfArrays:
{
var kvp = AstExpression.Var("kvp");
valuesAst = AstExpression.Map(
input: container.Ast,
@as: kvp,
@in: AstExpression.ArrayElemAt(kvp, 1));
break;
}
case DictionaryRepresentation.ArrayOfDocuments:
valuesAst = AstExpression.GetField(container.Ast, "v");
break;

default:
throw new ExpressionNotSupportedException(expression);
}

var serializer = ArraySerializerHelper.CreateSerializer(dictionarySerializer.ValueSerializer);
result = new TranslatedExpression(expression, valuesAst, serializer);
return true;
}

default:
throw new ExpressionNotSupportedException(expression);
}
}

throw new ExpressionNotSupportedException(expression, because: "serializer does not implement IBsonDictionarySerializer");
}

return false;
}

}
}
62 changes: 50 additions & 12 deletions ...essionTranslators/MethodTranslators/ContainsKeyMethodToAggregationExpressionTranslator.cs
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Expand Up @@ -36,27 +36,65 @@ public static TranslatedExpression Translate(TranslationContext context, MethodC
{
var dictionaryExpression = expression.Object;
var keyExpression = arguments[0];
return TranslateContainsKey(context, expression, dictionaryExpression, keyExpression);
}

throw new ExpressionNotSupportedException(expression);
}

var dictionaryTranslation = ExpressionToAggregationExpressionTranslator.Translate(context, dictionaryExpression);
var dictionarySerializer = GetDictionarySerializer(expression, dictionaryTranslation);
var dictionaryRepresentation = dictionarySerializer.DictionaryRepresentation;
public static TranslatedExpression TranslateContainsKey(TranslationContext context, Expression expression, Expression dictionaryExpression, Expression keyExpression)
{
var dictionaryTranslation = ExpressionToAggregationExpressionTranslator.Translate(context, dictionaryExpression);
var dictionarySerializer = GetDictionarySerializer(expression, dictionaryTranslation);
var dictionaryRepresentation = dictionarySerializer.DictionaryRepresentation;

AstExpression ast;
switch (dictionaryRepresentation)
{
case DictionaryRepresentation.Document:
AstExpression ast;
switch (dictionaryRepresentation)
{
case DictionaryRepresentation.Document:
{
var keyFieldName = GetKeyFieldName(context, expression, keyExpression, dictionarySerializer.KeySerializer);
ast = AstExpression.IsNotMissing(AstExpression.GetField(dictionaryTranslation.Ast, keyFieldName));
break;
}

default:
throw new ExpressionNotSupportedException(expression, because: $"ContainsKey is not supported when DictionaryRepresentation is: {dictionaryRepresentation}");
}
case DictionaryRepresentation.ArrayOfDocuments:
{
var keyFieldName = GetKeyFieldName(context, expression, keyExpression, dictionarySerializer.KeySerializer);
var (valueBinding, valueAst) = AstExpression.UseVarIfNotSimple("value", keyFieldName);
ast = AstExpression.Let(
var: valueBinding,
@in: AstExpression.Reduce(
input: dictionaryTranslation.Ast,
initialValue: false,
@in: AstExpression.Cond(
@if: AstExpression.Var("value"),
@then: true,
@else: AstExpression.Eq(AstExpression.GetField(AstExpression.Var("this"), "k"), valueAst))));
break;
}

case DictionaryRepresentation.ArrayOfArrays:
{
var keyFieldName = GetKeyFieldName(context, expression, keyExpression, dictionarySerializer.KeySerializer);
var (valueBinding, valueAst) = AstExpression.UseVarIfNotSimple("value", keyFieldName);
ast = AstExpression.Let(
var: valueBinding,
@in: AstExpression.Reduce(
input: dictionaryTranslation.Ast,
initialValue: false,
@in: AstExpression.Cond(
@if: AstExpression.Var("value"),
@then: true,
@else: AstExpression.Eq(AstExpression.ArrayElemAt(AstExpression.Var("this"), 0), valueAst))));
break;
}

return new TranslatedExpression(expression, ast, BooleanSerializer.Instance);
default:
throw new ExpressionNotSupportedException(expression, because: $"DictionaryRepresentation: {dictionaryRepresentation} is not supported.");
}

throw new ExpressionNotSupportedException(expression);
return new TranslatedExpression(expression, ast, BooleanSerializer.Instance);
}

private static AstExpression GetKeyFieldName(TranslationContext context, Expression expression, Expression keyExpression, IBsonSerializer keySerializer)
Expand Down
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