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Fix to #18555 - Query: when rewriting null semantics for comparisons with functions use function specific metadata to get better SQL #19607

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Jan 22, 2020
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Fix to #18555 - Query: when rewriting null semantics for comparisons with functions use function specific metadata to get better SQL #19607

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48 changes: 48 additions & 0 deletions src/EFCore.Relational/Query/ISqlExpressionFactory.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -131,6 +131,54 @@ SqlFunctionExpression Function(
[NotNull] Type returnType,
[CanBeNull] RelationalTypeMapping typeMapping = null);

SqlFunctionExpression Function(
[NotNull] string name,
[NotNull] IEnumerable<SqlExpression> arguments,
bool nullResultAllowed,
[NotNull] IEnumerable<bool> argumentsPropagateNullability,
[NotNull] Type returnType,
[CanBeNull] RelationalTypeMapping typeMapping = null);

SqlFunctionExpression Function(
[CanBeNull] string schema,
[NotNull] string name,
[NotNull] IEnumerable<SqlExpression> arguments,
bool nullResultAllowed,
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canBeNull would be better name

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will go with nullable/isnullable, just like column expression

[NotNull] IEnumerable<bool> argumentsPropagateNullability,
[NotNull] Type returnType,
[CanBeNull] RelationalTypeMapping typeMapping = null);

SqlFunctionExpression Function(
[CanBeNull] SqlExpression instance,
[NotNull] string name,
[NotNull] IEnumerable<SqlExpression> arguments,
bool nullResultAllowed,
bool instancePropagatesNullability,
[NotNull] IEnumerable<bool> argumentsPropagateNullability,
[NotNull] Type returnType,
[CanBeNull] RelationalTypeMapping typeMapping = null);

SqlFunctionExpression Function(
[NotNull] string name,
bool nullResultAllowed,
[NotNull] Type returnType,
[CanBeNull] RelationalTypeMapping typeMapping = null);

SqlFunctionExpression Function(
[NotNull] string schema,
[NotNull] string name,
bool nullResultAllowed,
[NotNull] Type returnType,
[CanBeNull] RelationalTypeMapping typeMapping = null);

SqlFunctionExpression Function(
[CanBeNull] SqlExpression instance,
[NotNull] string name,
bool nullResultAllowed,
bool instancePropagatesNullability,
[NotNull] Type returnType,
[CanBeNull] RelationalTypeMapping typeMapping = null);

ExistsExpression Exists([NotNull] SelectExpression subquery, bool negated);
InExpression In([NotNull] SqlExpression item, [NotNull] SqlExpression values, bool negated);
InExpression In([NotNull] SqlExpression item, [NotNull] SelectExpression subquery, bool negated);
Expand Down
116 changes: 87 additions & 29 deletions src/EFCore.Relational/Query/NullabilityBasedSqlProcessingExpressionVisitor.cs
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Expand Up @@ -898,8 +898,7 @@ private SqlExpression RewriteNullSemantics(
return sqlBinaryExpression.Update(left, right);
}

private SqlExpression SimplifyLogicalSqlBinaryExpression(
SqlBinaryExpression sqlBinaryExpression)
private SqlExpression SimplifyLogicalSqlBinaryExpression(SqlBinaryExpression sqlBinaryExpression)
{
var leftUnary = sqlBinaryExpression.Left as SqlUnaryExpression;
var rightUnary = sqlBinaryExpression.Right as SqlUnaryExpression;
Expand Down Expand Up @@ -1253,37 +1252,96 @@ protected virtual SqlExpression ProcessNullNotNull(
sqlUnaryExpression.TypeMapping));
}

case SqlFunctionExpression sqlFunctionExpression
when sqlFunctionExpression.IsBuiltIn && string.Equals("COALESCE", sqlFunctionExpression.Name, StringComparison.OrdinalIgnoreCase):
case SqlFunctionExpression sqlFunctionExpression:
{
// for coalesce:
// (a ?? b) == null -> a == null && b == null
// (a ?? b) != null -> a != null || b != null
var left = ProcessNullNotNull(
SqlExpressionFactory.MakeUnary(
sqlUnaryExpression.OperatorType,
sqlFunctionExpression.Arguments[0],
typeof(bool),
sqlUnaryExpression.TypeMapping),
operandNullable: null);
if (sqlFunctionExpression.IsBuiltIn && string.Equals("COALESCE", sqlFunctionExpression.Name, StringComparison.OrdinalIgnoreCase))
{
// for coalesce:
// (a ?? b) == null -> a == null && b == null
// (a ?? b) != null -> a != null || b != null
var left = ProcessNullNotNull(
SqlExpressionFactory.MakeUnary(
sqlUnaryExpression.OperatorType,
sqlFunctionExpression.Arguments[0],
typeof(bool),
sqlUnaryExpression.TypeMapping),
operandNullable: null);

var right = ProcessNullNotNull(
SqlExpressionFactory.MakeUnary(
sqlUnaryExpression.OperatorType,
sqlFunctionExpression.Arguments[1],
typeof(bool),
sqlUnaryExpression.TypeMapping),
operandNullable: null);

var right = ProcessNullNotNull(
SqlExpressionFactory.MakeUnary(
sqlUnaryExpression.OperatorType,
sqlFunctionExpression.Arguments[1],
typeof(bool),
sqlUnaryExpression.TypeMapping),
operandNullable: null);
return SimplifyLogicalSqlBinaryExpression(
SqlExpressionFactory.MakeBinary(
sqlUnaryExpression.OperatorType == ExpressionType.Equal
? ExpressionType.AndAlso
: ExpressionType.OrElse,
left,
right,
sqlUnaryExpression.TypeMapping));
}

return SimplifyLogicalSqlBinaryExpression(
SqlExpressionFactory.MakeBinary(
sqlUnaryExpression.OperatorType == ExpressionType.Equal
? ExpressionType.AndAlso
: ExpressionType.OrElse,
left,
right,
sqlUnaryExpression.TypeMapping));
if (!sqlFunctionExpression.NullResultAllowed)
{
// when we know that function can't be nullable:
// non_nullable_function() is null-> false
// non_nullable_function() is not null -> true
return SqlExpressionFactory.Constant(
sqlUnaryExpression.OperatorType == ExpressionType.NotEqual,
sqlUnaryExpression.TypeMapping);
}

// see if we can derive function nullability from it's instance and/or arguments
// rather than evaluating nullability of the entire function
var nullabilityPropagationElements = new List<SqlExpression>();
if (sqlFunctionExpression.Instance != null
&& sqlFunctionExpression.InstancPropagatesNullability == true)
{
nullabilityPropagationElements.Add(sqlFunctionExpression.Instance);
}

for (var i = 0; i < sqlFunctionExpression.Arguments.Count; i++)
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Check if is niladic to avoid for loop.

{
if (sqlFunctionExpression.ArgumentsPropagateNullability[i])
{
nullabilityPropagationElements.Add(sqlFunctionExpression.Arguments[i]);
}
}

if (nullabilityPropagationElements.Count > 0)
{
var result = ProcessNullNotNull(
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Using aggregate could be cleaner.

SqlExpressionFactory.MakeUnary(
sqlUnaryExpression.OperatorType,
nullabilityPropagationElements[0],
sqlUnaryExpression.Type,
sqlUnaryExpression.TypeMapping),
operandNullable: null);

foreach (var element in nullabilityPropagationElements.Skip(1))
{
result = SimplifyLogicalSqlBinaryExpression(
sqlUnaryExpression.OperatorType == ExpressionType.Equal
? SqlExpressionFactory.OrElse(
result,
ProcessNullNotNull(
SqlExpressionFactory.IsNull(element),
operandNullable: null))
: SqlExpressionFactory.AndAlso(
result,
ProcessNullNotNull(
SqlExpressionFactory.IsNotNull(element),
operandNullable: null)));
}

return result;
}
}
break;
}

return sqlUnaryExpression;
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2 changes: 2 additions & 0 deletions src/EFCore.Relational/Query/RelationalMethodCallTranslatorProvider.cs
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Expand Up @@ -56,6 +56,8 @@ public virtual SqlExpression Translate(
dbFunction.Schema,
dbFunction.Name,
arguments,
nullResultAllowed: true,
argumentsPropagateNullability: arguments.Select(a => true).ToList(),
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default should be false.

method.ReturnType);
}

Expand Down
57 changes: 49 additions & 8 deletions src/EFCore.Relational/Query/RelationalSqlTranslatingExpressionVisitor.cs
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Expand Up @@ -99,11 +99,20 @@ public virtual SqlExpression TranslateAverage([NotNull] Expression expression)
return inputType == typeof(float)
? SqlExpressionFactory.Convert(
SqlExpressionFactory.Function(
"AVG", new[] { sqlExpression }, typeof(double)),
"AVG",
new[] { sqlExpression },
nullResultAllowed: true,
argumentsPropagateNullability: new[] { false },
typeof(double)),
sqlExpression.Type,
sqlExpression.TypeMapping)
: (SqlExpression)SqlExpressionFactory.Function(
"AVG", new[] { sqlExpression }, sqlExpression.Type, sqlExpression.TypeMapping);
"AVG",
new[] { sqlExpression },
nullResultAllowed: true,
argumentsPropagateNullability: new[] { false },
sqlExpression.Type,
sqlExpression.TypeMapping);
}

public virtual SqlExpression TranslateCount([CanBeNull] Expression expression = null)
Expand All @@ -115,7 +124,12 @@ public virtual SqlExpression TranslateCount([CanBeNull] Expression expression =
}

return SqlExpressionFactory.ApplyDefaultTypeMapping(
SqlExpressionFactory.Function("COUNT", new[] { SqlExpressionFactory.Fragment("*") }, typeof(int)));
SqlExpressionFactory.Function(
"COUNT",
new[] { SqlExpressionFactory.Fragment("*") },
nullResultAllowed: false,
argumentsPropagateNullability: new[] { false },
typeof(int)));
}

public virtual SqlExpression TranslateLongCount([CanBeNull] Expression expression = null)
Expand All @@ -127,7 +141,12 @@ public virtual SqlExpression TranslateLongCount([CanBeNull] Expression expressio
}

return SqlExpressionFactory.ApplyDefaultTypeMapping(
SqlExpressionFactory.Function("COUNT", new[] { SqlExpressionFactory.Fragment("*") }, typeof(long)));
SqlExpressionFactory.Function(
"COUNT",
new[] { SqlExpressionFactory.Fragment("*") },
nullResultAllowed: false,
argumentsPropagateNullability: new[] { false },
typeof(long)));
}

public virtual SqlExpression TranslateMax([NotNull] Expression expression)
Expand All @@ -140,7 +159,13 @@ public virtual SqlExpression TranslateMax([NotNull] Expression expression)
}

return sqlExpression != null
? SqlExpressionFactory.Function("MAX", new[] { sqlExpression }, sqlExpression.Type, sqlExpression.TypeMapping)
? SqlExpressionFactory.Function(
"MAX",
new[] { sqlExpression },
nullResultAllowed: true,
argumentsPropagateNullability: new[] { false },
sqlExpression.Type,
sqlExpression.TypeMapping)
: null;
}

Expand All @@ -154,7 +179,13 @@ public virtual SqlExpression TranslateMin([NotNull] Expression expression)
}

return sqlExpression != null
? SqlExpressionFactory.Function("MIN", new[] { sqlExpression }, sqlExpression.Type, sqlExpression.TypeMapping)
? SqlExpressionFactory.Function(
"MIN",
new[] { sqlExpression },
nullResultAllowed: true,
argumentsPropagateNullability: new[] { false },
sqlExpression.Type,
sqlExpression.TypeMapping)
: null;
}

Expand All @@ -176,11 +207,21 @@ public virtual SqlExpression TranslateSum([NotNull] Expression expression)

return inputType == typeof(float)
? SqlExpressionFactory.Convert(
SqlExpressionFactory.Function("SUM", new[] { sqlExpression }, typeof(double)),
SqlExpressionFactory.Function(
"SUM",
new[] { sqlExpression },
nullResultAllowed: true,
argumentsPropagateNullability: new[] { false },
typeof(double)),
inputType,
sqlExpression.TypeMapping)
: (SqlExpression)SqlExpressionFactory.Function(
"SUM", new[] { sqlExpression }, inputType, sqlExpression.TypeMapping);
"SUM",
new[] { sqlExpression },
nullResultAllowed: true,
argumentsPropagateNullability: new[] { false },
inputType,
sqlExpression.TypeMapping);
}

private sealed class SqlTypeMappingVerifyingExpressionVisitor : ExpressionVisitor
Expand Down
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