Round brackets for SqlQueryExpression for MySql v5.7

Author: alex-kulakov

Orm/Xtensive.Orm.MySql/Sql.Drivers.MySql/v5_7/Compiler.cs

@@ -4,10 +4,47 @@
 // Created by: Alexey Kulakov
 // Created:    2022.02.03
 
+using Xtensive.Sql.Compiler;
+using Xtensive.Sql.Dml;
+
 namespace Xtensive.Sql.Drivers.MySql.v5_7
 {
   internal class Compiler : v5_6.Compiler
   {
+    /// <inheritdoc/>
+    public override void Visit(SqlQueryExpression node)
+    {
+      using (context.EnterScope(node)) {
+        var wrapLeft = node.Left is SqlSelect sL
+          && (sL.OrderBy.Count > 0 || sL.HasLimit || sL.Lock != SqlLockType.Empty);
+        var wrapRight = node.Left is SqlSelect sR
+          && (sR.OrderBy.Count > 0 || sR.HasLimit || sR.Lock != SqlLockType.Empty);
+
+        AppendTranslatedEntry(node);
+        if (wrapLeft) {
+          _ = context.Output.Append("(");
+          node.Left.AcceptVisitor(this);
+          _ = context.Output.Append(")");
+        }
+        else {
+          node.Left.AcceptVisitor(this);
+        }
+
+        AppendTranslated(node.NodeType);
+        AppendTranslated(node, QueryExpressionSection.All);
+
+        if (wrapRight) {
+          _ = context.Output.Append("(");
+          node.Right.AcceptVisitor(this);
+          _ = context.Output.Append(")");
+        }
+        else {
+          node.Right.AcceptVisitor(this);
+        }
+        AppendTranslatedExit(node);
+      }
+    }
+
     // Constructors
 
     public Compiler(SqlDriver driver)