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LINQ: Fixes NullReferenceException when attempting to generate SQL for a LINQ expression which performs static field or property access #3190

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Merged
j82w merged 1 commit into from
May 12, 2022
Merged

LINQ: Fixes NullReferenceException when attempting to generate SQL for a LINQ expression which performs static field or property access #3190

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17 changes: 12 additions & 5 deletions Microsoft.Azure.Cosmos/src/Linq/SubtreeEvaluator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ protected override Expression VisitMemberInit(MemberInitExpression node)

private Expression EvaluateMemberAccess(Expression expression)
{
while (expression.CanReduce)
while (expression?.CanReduce ?? false)
{
expression = expression.Reduce();
}
Expand All @@ -57,7 +57,7 @@ private Expression EvaluateMemberAccess(Expression expression)
// This is done because the compilation of a delegate takes a global lock which causes highly
// threaded clients to exhibit async-over-sync thread exhaustion behaviour on this call path
// even when doing relatively straightforward queries.
if (!(expression is MemberExpression memberExpression))
if (expression is not MemberExpression memberExpression)
{
return expression;
}
Expand All @@ -66,19 +66,26 @@ private Expression EvaluateMemberAccess(Expression expression)
// nested property access (x.y.z) without needing to fall back on delegate compilation.
Expression targetExpression = this.EvaluateMemberAccess(memberExpression.Expression);

if (!(targetExpression is ConstantExpression targetConstant))
// NOTE: When evaluating static field or property access, we may have a null targetExpression.
// In this situation, we should pass the null value to the GetValue(...) methods below to
// indicate that we are accessing a static member.
ConstantExpression targetConstant = targetExpression as ConstantExpression;

// If we have a target expression but it cannot be resolved to a constant, then we should skip
// using reflectoin here and instead rely on the fallback delegate compilation approach.
if (targetExpression is not null && targetConstant is null)
{
return expression;
}

if (memberExpression.Member is FieldInfo fieldInfo)
{
return Expression.Constant(fieldInfo.GetValue(targetConstant.Value), memberExpression.Type);
return Expression.Constant(fieldInfo.GetValue(targetConstant?.Value), memberExpression.Type);
}

if (memberExpression.Member is PropertyInfo propertyInfo)
{
return Expression.Constant(propertyInfo.GetValue(targetConstant.Value), memberExpression.Type);
return Expression.Constant(propertyInfo.GetValue(targetConstant?.Value), memberExpression.Type);
}

return expression;
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36 changes: 36 additions & 0 deletions ...EmulatorTests/BaselineTest/TestBaseline/LinqTranslationBaselineTests.TestMemberAccess.xml
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Expand Up @@ -35,4 +35,40 @@ FROM root
WHERE (root["NumericField"] = 3)]]></SqlQuery>
</Output>
</Result>
<Result>
<Input>
<Description><![CDATA[Filter on Static Field value]]></Description>
<Expression><![CDATA[query.Where(doc => (doc.NumericField == AmbientContextObject.StaticFieldAccess))]]></Expression>
</Input>
<Output>
<SqlQuery><![CDATA[
SELECT VALUE root
FROM root
WHERE (root["NumericField"] = 4)]]></SqlQuery>
</Output>
</Result>
<Result>
<Input>
<Description><![CDATA[Filter on Static Property value]]></Description>
<Expression><![CDATA[query.Where(doc => (doc.NumericField == AmbientContextObject.StaticPropertyAccess))]]></Expression>
</Input>
<Output>
<SqlQuery><![CDATA[
SELECT VALUE root
FROM root
WHERE (root["NumericField"] = 5)]]></SqlQuery>
</Output>
</Result>
<Result>
<Input>
<Description><![CDATA[Filter on Const value]]></Description>
<Expression><![CDATA[query.Where(doc => (doc.NumericField == 6))]]></Expression>
</Input>
<Output>
<SqlQuery><![CDATA[
SELECT VALUE root
FROM root
WHERE (root["NumericField"] = 6)]]></SqlQuery>
</Output>
</Result>
</Results>
14 changes: 13 additions & 1 deletion ...t.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/LinqTranslationBaselineTests.cs
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Expand Up @@ -151,7 +151,16 @@ internal class AmbientContextObject

public double PropertyAccess { get; set; }

public double MethodAccess() => 1.0;
public double MethodAccess()
{
return 1.0;
}

public static double StaticFieldAccess = 4.0;

public static double StaticPropertyAccess => 5.0;

public const double ConstAccess = 6.0;
}

[TestMethod]
Expand Down Expand Up @@ -560,6 +569,9 @@ public void TestMemberAccess()
// performance boost, especially under highly concurrent workloads).
new LinqTestInput("Filter on Field value", b => getQuery(b).Where(doc => doc.NumericField == ambientContext.FieldAccess)),
new LinqTestInput("Filter on Property value", b => getQuery(b).Where(doc => doc.NumericField == ambientContext.PropertyAccess)),
new LinqTestInput("Filter on Static Field value", b => getQuery(b).Where(doc => doc.NumericField == AmbientContextObject.StaticFieldAccess)),
new LinqTestInput("Filter on Static Property value", b => getQuery(b).Where(doc => doc.NumericField == AmbientContextObject.StaticPropertyAccess)),
new LinqTestInput("Filter on Const value", b => getQuery(b).Where(doc => doc.NumericField == AmbientContextObject.ConstAccess)),
};
this.ExecuteTestSuite(inputs);
}
Expand Down