Prefer equality in boolean comparisons

They can take advantage of indexing.
dotnet · Jul 12, 2024 · 0f40cf7 · 0f40cf7
1 parent bc170c7
commit 0f40cf7
Showing 1 changed file with 25 additions and 1 deletion.
diff --git a/src/EFCore.Relational/Query/SqlNullabilityProcessor.cs b/src/EFCore.Relational/Query/SqlNullabilityProcessor.cs
@@ -1289,6 +1289,7 @@ protected virtual SqlExpression VisitSqlBinary(
                 right,
                 leftNullable,
                 rightNullable,
+                optimize,
                 out nullable);
 
             if (optimized is SqlUnaryExpression { Operand: ColumnExpression optimizedUnaryColumnOperand } optimizedUnary)
@@ -1623,6 +1624,7 @@ private SqlExpression ProcessJoinPredicate(SqlExpression predicate)
                     right,
                     leftNullable,
                     rightNullable,
+                    optimize: true,
                     out _);
 
                 return result;
@@ -1649,6 +1651,7 @@ private SqlExpression OptimizeComparison(
         SqlExpression right,
         bool leftNullable,
         bool rightNullable,
+        bool optimize,
         out bool nullable)
     {
         var leftNullValue = leftNullable && left is SqlConstantExpression or SqlParameterExpression;
@@ -1752,7 +1755,24 @@ private SqlExpression OptimizeComparison(
 
             nullable = false;
 
-            return sqlBinaryExpression.OperatorType == ExpressionType.Equal ^ leftNegated == rightNegated
+            var notEqual = sqlBinaryExpression.OperatorType == ExpressionType.Equal ^ leftNegated == rightNegated;
+
+            // prefer equality in predicates
+            if (optimize && notEqual && left.Type == typeof(bool))
+            {
+                if (right is ColumnExpression && (left is not ColumnExpression || leftNegated))
+                {
+                    left = _sqlExpressionFactory.Not(left);
+                }
+                else
+                {
+                    right = _sqlExpressionFactory.Not(right);
+                }
+
+                return _sqlExpressionFactory.Equal(left, right);
+            }
+
+            return notEqual
                 ? _sqlExpressionFactory.NotEqual(left, right)
                 : _sqlExpressionFactory.Equal(left, right);
         }
@@ -1798,6 +1818,10 @@ private SqlExpression RewriteNullSemantics(
         {
             body = _sqlExpressionFactory.Equal(left, right);
         }
+        else if (optimize && sqlBinaryExpression.OperatorType == ExpressionType.Equal)
+        {
+            body = _sqlExpressionFactory.Equal(leftUnary ?? left, rightUnary ?? right);
+        }
         else
         {
             // a == !b and !a == b in SQL evaluate the same as a != b