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Added support for nullable cursor keys #8431

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38429e0
Added support for nullable cursor keys
glen-84 Jul 8, 2025
b629c58
Fixed tests
glen-84 Jul 8, 2025
72ff12d
Merge branch 'main' into gai/nullable-cursor-keys
glen-84 Jul 8, 2025
113732e
Merge branch 'main' into gai/nullable-cursor-keys
glen-84 Jul 9, 2025
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4 changes: 4 additions & 0 deletions src/Directory.Packages.props
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@
<PackageVersion Include="Squadron.RabbitMQ" Version="0.25.0-preview.2" />
<PackageVersion Include="Squadron.RavenDB" Version="0.25.0-preview.2" />
<PackageVersion Include="Squadron.Redis" Version="0.25.0-preview.2" />
<PackageVersion Include="Squadron.SqlServer" Version="0.25.0-preview.2" />
<PackageVersion Include="Squadron.AzureStorage" Version="0.25.0-preview.2" />
<PackageVersion Include="StackExchange.Redis" Version="2.6.80" />
<PackageVersion Include="System.Collections.Immutable" Version="8.0.0" />
Expand All @@ -78,6 +79,7 @@
<PackageVersion Include="Microsoft.EntityFrameworkCore.InMemory" Version="10.0.0-preview.5.25277.114" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.Relational" Version="10.0.0-preview.5.25277.114" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.Sqlite" Version="10.0.0-preview.5.25277.114" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.SqlServer" Version="10.0.0-preview.5.25277.114" />
<PackageVersion Include="Microsoft.Extensions.Caching.Memory" Version="10.0.0-preview.5.25277.114" />
<PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="10.0.0-preview.5.25277.114" />
<PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.0-preview.5.25277.114" />
Expand All @@ -101,6 +103,7 @@
<PackageVersion Include="Microsoft.EntityFrameworkCore.InMemory" Version="9.0.4" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.Relational" Version="9.0.4" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.Sqlite" Version="9.0.4" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.SqlServer" Version="9.0.4" />
<PackageVersion Include="Microsoft.Extensions.Caching.Memory" Version="9.0.4" />
<PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="9.0.4" />
<PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="9.0.4" />
Expand All @@ -124,6 +127,7 @@
<PackageVersion Include="Microsoft.EntityFrameworkCore.InMemory" Version="8.0.15" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.Relational" Version="8.0.15" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.Sqlite" Version="8.0.15" />
<PackageVersion Include="Microsoft.EntityFrameworkCore.SqlServer" Version="8.0.15" />
<PackageVersion Include="Microsoft.Extensions.Caching.Memory" Version="8.0.1" />
<PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
<PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="8.0.2" />
Expand Down
276 changes: 261 additions & 15 deletions src/GreenDonut/src/GreenDonut.Data.EntityFramework/Expressions/ExpressionHelpers.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,10 @@ internal static class ExpressionHelpers
.GetMethod(nameof(CreateAndConvertParameter), BindingFlags.NonPublic | BindingFlags.Static)!;

private static readonly ConcurrentDictionary<Type, Func<object?, Expression>> s_cachedConverters = new();
private static readonly NullabilityInfoContext s_nullabilityInfoContext = new();
private static readonly Expression s_null = Expression.Constant(null);
private static readonly Expression s_false = Expression.Constant(false);
private static readonly Expression s_zero = Expression.Constant(0);

/// <summary>
/// Builds a where expression that can be used to slice a dataset.
Expand All @@ -28,6 +32,9 @@ internal static class ExpressionHelpers
/// <param name="forward">
/// Defines how the dataset is sorted.
/// </param>
/// <param name="nullOrdering">
/// Defines the null ordering to be used.
/// </param>
/// <typeparam name="T">
/// The entity type.
/// </typeparam>
Expand All @@ -43,7 +50,8 @@ internal static class ExpressionHelpers
public static (Expression<Func<T, bool>> WhereExpression, int Offset) BuildWhereExpression<T>(
ReadOnlySpan<CursorKey> keys,
Cursor cursor,
bool forward)
bool forward,
NullOrdering nullOrdering)
{
if (keys.Length == 0)
{
Expand All @@ -58,14 +66,16 @@ public static (Expression<Func<T, bool>> WhereExpression, int Offset) BuildWhere
var cursorExpr = new Expression[cursor.Values.Length];
for (var i = 0; i < cursor.Values.Length; i++)
{
cursorExpr[i] = CreateParameter(cursor.Values[i], keys[i].Expression.ReturnType);
var parameterType = Nullable.GetUnderlyingType(keys[i].Expression.ReturnType)
?? keys[i].Expression.ReturnType;

cursorExpr[i] = CreateParameter(cursor.Values[i], parameterType);
}

var handled = new List<CursorKey>();
Expression? expression = null;

var parameter = Expression.Parameter(typeof(T), "t");
var zero = Expression.Constant(0);

for (var i = 0; i < keys.Length; i++)
{
Expand All @@ -77,24 +87,50 @@ public static (Expression<Func<T, bool>> WhereExpression, int Offset) BuildWhere
{
var handledKey = handled[j];

keyExpr = Expression.Equal(
Expression.Call(ReplaceParameter(handledKey.Expression, parameter), handledKey.CompareMethod,
cursorExpr[j]), zero);
keyExpr = BuildEqualToKeyExpr(
handledKey,
parameter,
cursor.Values[j],
cursorExpr[j]);

current = current is null ? keyExpr : Expression.AndAlso(current, keyExpr);
}

var keyIsNullable = IsNullable(key.Expression);

if (keyIsNullable && nullOrdering == NullOrdering.Unspecified)
{
throw new Exception(
"The NullOrdering option must be specified in the paging options or " +
"arguments when using nullable keys.");
}

var greaterThan = forward
? key.Direction == CursorKeyDirection.Ascending
: key.Direction == CursorKeyDirection.Descending;

keyExpr = greaterThan
? Expression.GreaterThan(
Expression.Call(ReplaceParameter(key.Expression, parameter), key.CompareMethod, cursorExpr[i]),
zero)
: Expression.LessThan(
Expression.Call(ReplaceParameter(key.Expression, parameter), key.CompareMethod, cursorExpr[i]),
zero);
if (greaterThan)
{
keyExpr =
BuildGreaterThanKeyExpr(
key,
parameter,
cursor.Values[i],
keyIsNullable,
nullOrdering,
cursorExpr[i]);
}
else
{
keyExpr =
BuildLessThanKeyExpr(
key,
parameter,
cursor.Values[i],
keyIsNullable,
nullOrdering,
cursorExpr[i]);
}

current = current is null ? keyExpr : Expression.AndAlso(current, keyExpr);
expression = expression is null ? current : Expression.OrElse(expression, current);
Expand All @@ -104,6 +140,207 @@ public static (Expression<Func<T, bool>> WhereExpression, int Offset) BuildWhere
return (Expression.Lambda<Func<T, bool>>(expression!, parameter), cursor.Offset ?? 0);
}

private static Expression BuildEqualToKeyExpr(
CursorKey cursorKey,
ParameterExpression parameter,
object? cursorValue,
Expression cursorExpr)
{
var keyIsNullable = IsNullable(cursorKey.Expression);
var keyExpr = ReplaceParameter(cursorKey.Expression, parameter);

// Access the value of the key if it is a nullable value type.
var keyValueExpr = cursorKey.Expression.ReturnType.IsValueType && keyIsNullable
? Expression.Property(keyExpr, "Value")
: keyExpr;

if (keyIsNullable)
{
if (cursorValue is null)
{
// SQL: WHERE key IS NULL.
keyExpr = Expression.Equal(keyExpr, s_null);
}
else
{
// SQL: WHERE key = cursorValue.
keyExpr = Expression.Equal(
Expression.Call(keyValueExpr, cursorKey.CompareMethod, cursorExpr),
s_zero);
}
}
else
{
// SQL: WHERE key = cursorValue.
keyExpr = Expression.Equal(
Expression.Call(keyExpr, cursorKey.CompareMethod, cursorExpr),
s_zero);
}

return keyExpr;
}

private static Expression BuildGreaterThanKeyExpr(
CursorKey cursorKey,
ParameterExpression parameter,
object? cursorValue,
bool keyIsNullable,
NullOrdering nullOrdering,
Expression cursorExpr)
{
var keyExpr = ReplaceParameter(cursorKey.Expression, parameter);

// Access the value of the key if it is a nullable value type.
var keyValueExpr =
cursorKey.Expression.ReturnType.IsValueType && keyIsNullable
? Expression.Property(keyExpr, "Value")
: keyExpr;

if (keyIsNullable)
{
if (cursorValue is null)
{
keyExpr = nullOrdering == NullOrdering.NativeNullsFirst
// With nulls first, any non-null value is greater than null.
// SQL: WHERE key IS NOT NULL.
? Expression.NotEqual(keyExpr, s_null)
// With nulls last, no value is greater than null.
// SQL: WHERE false.
: s_false;
}
else
{
if (nullOrdering == NullOrdering.NativeNullsFirst)
{
// SQL: WHERE key > cursorValue.
keyExpr = Expression.GreaterThan(
Expression.Call(keyValueExpr, cursorKey.CompareMethod, cursorExpr),
s_zero);
}
else
{
// When nulls are last, null is greater than any non-null value.
// SQL: WHERE key > cursorValue OR key IS NULL.
keyExpr = Expression.Or(
Expression.GreaterThan(
Expression.Call(keyValueExpr, cursorKey.CompareMethod, cursorExpr),
s_zero),
Expression.Equal(keyExpr, s_null));
}
}
}
else
{
// SQL: WHERE key > cursorValue.
keyExpr = Expression.GreaterThan(
Expression.Call(keyExpr, cursorKey.CompareMethod, cursorExpr),
s_zero);
}

return keyExpr;
}

private static Expression BuildLessThanKeyExpr(
CursorKey cursorKey,
ParameterExpression parameter,
object? cursorValue,
bool keyIsNullable,
NullOrdering nullOrdering,
Expression cursorExpr)
{
var keyExpr = ReplaceParameter(cursorKey.Expression, parameter);

// Access the value of the key if it is a nullable value type.
var keyValueExpr =
cursorKey.Expression.ReturnType.IsValueType && keyIsNullable
? Expression.Property(keyExpr, "Value")
: keyExpr;

if (keyIsNullable)
{
if (cursorValue is null)
{
keyExpr = nullOrdering == NullOrdering.NativeNullsFirst
// With nulls first, no value is less than null.
// SQL: WHERE false.
? s_false
// With nulls last, any non-null value is less than null.
// SQL: WHERE key IS NOT NULL.
: Expression.NotEqual(keyExpr, s_null);
}
else
{
if (nullOrdering == NullOrdering.NativeNullsFirst)
{
// With nulls first, null is less than any non-null value.
// SQL: WHERE key < cursorValue OR key IS NULL.
keyExpr = Expression.Or(
Expression.LessThan(
Expression.Call(keyValueExpr, cursorKey.CompareMethod, cursorExpr),
s_zero),
Expression.Equal(keyExpr, s_null));
}
else
{
// SQL: WHERE key < cursorValue.
keyExpr = Expression.LessThan(
Expression.Call(keyValueExpr, cursorKey.CompareMethod, cursorExpr),
s_zero);
}
}
}
else
{
// SQL: WHERE key < cursorValue.
keyExpr = Expression.LessThan(
Expression.Call(keyExpr, cursorKey.CompareMethod, cursorExpr),
s_zero);
}

return keyExpr;
}

private static bool IsNullable(LambdaExpression expression)
{
if (expression.ReturnType.IsValueType)
{
return Nullable.GetUnderlyingType(expression.ReturnType) is not null;
}

var propertyInfo = expression.Body switch
{
MemberExpression
{
Member: PropertyInfo p
} => p,
BinaryExpression
{
NodeType: ExpressionType.Coalesce,
Right: MemberExpression { Member: PropertyInfo p }
} => p,
_ => null
};

if (propertyInfo is not null)
{
var nullability = s_nullabilityInfoContext.Create(propertyInfo).ReadState;

switch (nullability)
{
case NullabilityState.Nullable:
return true;
case NullabilityState.NotNull:
return false;
case NullabilityState.Unknown:
break;
default:
throw new InvalidOperationException();
}
}

throw new Exception("The nullability of the cursor key could not be determined.");
}

/// <summary>
/// Build the select expression for a batch paging expression that uses grouping.
/// </summary>
Expand Down Expand Up @@ -184,7 +421,11 @@ public static BatchExpression<TK, TV> BuildBatchExpression<TK, TV>(
if (arguments.After is not null)
{
cursor = CursorParser.Parse(arguments.After, keys);
var (whereExpr, cursorOffset) = BuildWhereExpression<TV>(keys, cursor, forward: true);
var (whereExpr, cursorOffset) = BuildWhereExpression<TV>(
keys,
cursor,
forward: true,
arguments.NullOrdering);
source = Expression.Call(typeof(Enumerable), "Where", [typeof(TV)], source, whereExpr);
offset = cursorOffset;

Expand All @@ -204,7 +445,12 @@ public static BatchExpression<TK, TV> BuildBatchExpression<TK, TV>(
}

cursor = CursorParser.Parse(arguments.Before, keys);
var (whereExpr, cursorOffset) = BuildWhereExpression<TV>(keys, cursor, forward: false);
var (whereExpr, cursorOffset) = BuildWhereExpression<TV>(
keys,
cursor,
forward:
false,
arguments.NullOrdering);
source = Expression.Call(typeof(Enumerable), "Where", [typeof(TV)], source, whereExpr);
offset = cursorOffset;
}
Expand Down
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