Improvement of string operations within queries

ChangeLog/7.2.0-Beta-2-dev.txt

@@ -1 +1,6 @@
-[main] Upgrade hints change names of constructors' string parameters for better understanding of what suppose to be in them.
+[main] Upgrade hints change names of constructors' string parameters for better understanding of what suppose to be in them.
+[main] Improved string operations Trim/TrimStart/TrimEnd support
+[mysql] SqlDml.NullIf function now correctly translated
+[mysql] Improved support for string.PadLeft/PadRight opertaions
+[sqlite] Fixed string.Lenght translation
+[sqlite] Added support for string.PadLeft/PadRight operations

Orm/Xtensive.Orm.MySql/Sql.Drivers.MySql/v5_0/Compiler.cs

@@ -160,7 +160,7 @@ public override void Visit(SqlFunctionCall node)
           return;
         case SqlFunctionType.PadLeft:
         case SqlFunctionType.PadRight:
-          SqlHelper.GenericPad(node).AcceptVisitor(this);
+          SqlHelper.GenericPad(node, true).AcceptVisitor(this);
           return;
         case SqlFunctionType.Rand:
           SqlDml.FunctionCall(translator.TranslateToString(SqlFunctionType.Rand)).AcceptVisitor(this);

Orm/Xtensive.Orm.MySql/Sql.Drivers.MySql/v5_0/Translator.cs

@@ -101,7 +101,6 @@ public override void Translate(IOutput output, SqlFunctionType type)
         case SqlFunctionType.CurrentUser:
           _ = output.Append("CURRENT_USER()"); break;
         case SqlFunctionType.SessionUser: _ = output.Append("SESSION_USER()"); break;
-        case SqlFunctionType.NullIf: _ = output.Append("IFNULL"); break;
         //datetime/timespan
         case SqlFunctionType.DateTimeTruncate: _ = output.Append("DATE"); break;
         case SqlFunctionType.CurrentDate: _ = output.Append("CURDATE()"); break;

Orm/Xtensive.Orm.Sqlite/Sql.Drivers.Sqlite/v3/Compiler.cs

@@ -151,10 +151,11 @@ public override void Visit(SqlFunctionCall node)
       var arguments = node.Arguments;
       switch (node.FunctionType) {
         case SqlFunctionType.CharLength:
-          (SqlDml.FunctionCall("LENGTH", arguments) / 2).AcceptVisitor(this);
+          SqlDml.FunctionCall("LENGTH", arguments).AcceptVisitor(this);
           return;
         case SqlFunctionType.PadLeft:
         case SqlFunctionType.PadRight:
+          Visit(EmulateLpadRpad(arguments, node.FunctionType is SqlFunctionType.PadLeft));
           return;
         case SqlFunctionType.Concat:
           var nod = arguments[0];
@@ -631,6 +632,42 @@ private static SqlDateTimePart ConvertDateTimeOffsetPartToDateTimePart(SqlDateTi
       };
     }
 
+    private static SqlCase EmulateLpadRpad(IReadOnlyList<SqlExpression> arguments, bool isLpad)
+    {
+      var operand = arguments[0];
+      var charcount = arguments[1];
+      if (charcount is not SqlLiteral<int> intWidth) {
+        // Since we emulate function with  contatination, we need to know total width
+        // to calculate prefix
+        throw SqlHelper.NotSupported("PadLeft/PadRight with expressions as total width.");
+      }
+      var totalWidth = intWidth.Value;
+
+      var padChar = arguments switch {
+        _ when arguments.Count == 3 && arguments[2] is SqlLiteral<char> charLiteral => charLiteral.Value,
+        _ when arguments.Count == 2 => ' ',
+        _ => throw new NotSupportedException()
+      };
+
+      var paddingString = SqlDml.Literal(new string(Enumerable.Repeat(padChar, intWidth.Value).ToArray()));
+
+      var padExpression = isLpad
+        ? SqlDml.Substring(
+            SqlDml.Concat(paddingString, operand),
+            SqlDml.Literal(-totalWidth - 1),// handles '+1' operation in translation of substring function call
+            SqlDml.Literal(totalWidth))
+        : SqlDml.Substring(
+            SqlDml.Concat(operand, paddingString),
+            SqlDml.Literal(0), // handles '+1' operation in translation of substring function call
+            SqlDml.Literal(totalWidth));
+
+      var @case = SqlDml.Case();
+      _ = @case.Add(SqlDml.CharLength(operand) >= charcount, operand);
+      @case.Else = padExpression;
+      return @case;
+    }
+
+
     // Constructors
 
     /// <param name="driver">The driver.</param>

Orm/Xtensive.Orm.Tests/Linq/SelectTest.cs

@@ -768,118 +768,6 @@ where invoice.InvoiceId > 0 && invoice.InvoiceId < 50
       }
     }
 
-    [Test]
-    public void SelectStringIndexerTest()
-    {
-      var result =
-        Session.Query.All<Customer>()
-          .Select(c => new {
-            String = c.CustomerId,
-            Char0 = c.Email[0],
-            Char1 = c.Email[1],
-            Char2 = c.Email[2],
-            Char3 = c.Email[3],
-            Char4 = c.Email[4],
-          })
-          .ToArray()
-          .OrderBy(item => item.String)
-          .ToArray();
-      var expected = Customers
-          .Select(c => new {
-            String = c.CustomerId,
-            Char0 = c.Email[0],
-            Char1 = c.Email[1],
-            Char2 = c.Email[2],
-            Char3 = c.Email[3],
-            Char4 = c.Email[4],
-          })
-          .OrderBy(item => item.String)
-          .ToArray();
-      Assert.AreEqual(expected.Length, result.Length);
-      for (var i = 0; i < expected.Length; i++) {
-        Assert.AreEqual(expected[0].String, result[0].String);
-        Assert.AreEqual(expected[0].Char0, result[0].Char0);
-        Assert.AreEqual(expected[0].Char1, result[0].Char1);
-        Assert.AreEqual(expected[0].Char2, result[0].Char2);
-        Assert.AreEqual(expected[0].Char3, result[0].Char3);
-        Assert.AreEqual(expected[0].Char4, result[0].Char4);
-      }
-    }
-
-    [Test]
-    public void SelectIndexOfTest()
-    {
-      var _char = 'A';
-      var result =
-        Session.Query.All<Customer>()
-          .Select(c => new {
-            String = c.FirstName,
-            IndexOfChar = c.FirstName.IndexOf(_char),
-            IndexOfCharStart = c.FirstName.IndexOf(_char, 1),
-            IndexOfCharStartCount = c.FirstName.IndexOf(_char, 1, 1),
-            IndexOfString = c.FirstName.IndexOf(_char.ToString()),
-            IndexOfStringStart = c.FirstName.IndexOf(_char.ToString(), 1),
-            IndexOfStringStartCount = c.FirstName.IndexOf(_char.ToString(), 1, 1)
-          })
-          .ToArray()
-          .OrderBy(item => item.String)
-          .ToArray();
-      var expected = Customers
-          .Select(c => new {
-            String = c.FirstName,
-            IndexOfChar = c.FirstName.IndexOf(_char),
-            IndexOfCharStart = c.FirstName.IndexOf(_char, 1),
-            IndexOfCharStartCount = c.FirstName.IndexOf(_char, 1, 1),
-            IndexOfString = c.FirstName.IndexOf(_char.ToString()),
-            IndexOfStringStart = c.FirstName.IndexOf(_char.ToString(), 1),
-            IndexOfStringStartCount = c.FirstName.IndexOf(_char.ToString(), 1, 1)
-          })
-          .OrderBy(item => item.String)
-          .ToArray();
-      Assert.AreEqual(expected.Length, result.Length);
-      for (var i = 0; i < expected.Length; i++) {
-        Assert.AreEqual(expected[i].String, result[i].String);
-        Assert.AreEqual(expected[i].IndexOfChar, result[i].IndexOfChar);
-        Assert.AreEqual(expected[i].IndexOfCharStart, result[i].IndexOfCharStart);
-        Assert.AreEqual(expected[i].IndexOfCharStartCount, result[i].IndexOfCharStartCount);
-        Assert.AreEqual(expected[i].IndexOfString, result[i].IndexOfString);
-        Assert.AreEqual(expected[i].IndexOfStringStart, result[i].IndexOfStringStart);
-        Assert.AreEqual(expected[i].IndexOfStringStartCount, result[i].IndexOfStringStartCount);
-      }
-    }
-
-    [Test]
-    public void SelectStringContainsTest1()
-    {
-      Require.ProviderIs(StorageProvider.Sqlite | StorageProvider.SqlServer | StorageProvider.MySql);
-      var result =
-        Session.Query.All<Customer>()
-          .Where(c => c.FirstName.Contains('L'))
-          .OrderBy(c => c.CustomerId)
-          .ToArray();
-      var expected = Customers
-          .Where(c => c.FirstName.Contains('L') || c.FirstName.Contains('l'))
-          .OrderBy(c => c.CustomerId)
-          .ToArray();
-      Assert.IsTrue(expected.SequenceEqual(result));
-    }
-
-    [Test]
-    public void SelectStringContainsTest2()
-    {
-      Require.ProviderIsNot(StorageProvider.Sqlite | StorageProvider.SqlServer | StorageProvider.MySql);
-      var result =
-        Session.Query.All<Customer>()
-          .Where(c => c.FirstName.Contains('L'))
-          .OrderBy(c => c.CustomerId)
-          .ToArray();
-      var expected = Customers
-          .Where(c => c.FirstName.Contains('L'))
-          .OrderBy(c => c.CustomerId)
-          .ToArray();
-      Assert.IsTrue(expected.SequenceEqual(result));
-    }
-
     [Test]
     public void SelectDateTimeTimeSpanTest()
     {