Use constant size for db string params

Author: mythz

src/ServiceStack.OrmLite/Converters/StringConverter.cs

@@ -36,6 +36,16 @@ public virtual string GetColumnDefinition(int? stringLength)
                 : $"VARCHAR({stringLength.GetValueOrDefault(StringLength)})";
         }
 
+        public override void InitDbParam(IDbDataParameter p, Type fieldType)
+        {
+            base.InitDbParam(p, fieldType);
+
+            if (p.Size == default)
+            {
+                p.Size = StringLength;
+            }
+        }
+
         public override object FromDbValue(Type fieldType, object value)
         {
             if (value is string strValue)

src/ServiceStack.OrmLite/OrmLiteDialectProviderBase.cs

@@ -968,6 +968,12 @@ public virtual void SetParameterValue<T>(FieldDefinition fieldDef, IDataParamete
         {
             var value = GetValueOrDbNull<T>(fieldDef, obj);
             p.Value = value;
+
+            if (value is string s && p is IDbDataParameter dataParam && dataParam.Size > 0 && s?.Length > dataParam.Size)
+            {
+                // db param Size set in StringConverter
+                dataParam.Size = s.Length;
+            }
         }
 
         protected virtual object GetValue<T>(FieldDefinition fieldDef, object obj)

tests/ServiceStack.OrmLite.Tests/OrmLiteUpdateTests.cs

@@ -702,6 +702,38 @@ public void Can_UpdateOnly_fields_case_insensitive()
                 Assert.That(updatedRow.Age, Is.EqualTo(27));
             }
         }
+
+        [Test]
+        public void Does_use_constant_size_string_params()
+        {
+            using (var db = OpenDbConnection())
+            {
+                db.DropAndCreateTable<Person>();
+
+                var converter = db.GetDialectProvider().GetStringConverter();
+
+                void AssertDbStringParamSizes(IDbCommand cmd)
+                {
+                    foreach (IDbDataParameter p in cmd.Parameters)
+                    {
+                        if (p.Value is string s)
+                        {
+                            Assert.That(p.Size, Is.EqualTo(converter.StringLength));
+                        }
+                    }
+                }
+                
+                var hendrix = new Person(1, "Jimi", "Hendrix", 27);
+                db.Insert(hendrix, commandFilter: AssertDbStringParamSizes);
+
+                hendrix.FirstName = "Updated";
+
+                db.Update(hendrix, commandFilter: AssertDbStringParamSizes);
+
+                var row = db.SingleById<Person>(hendrix.Id);
+                Assert.That(row.FirstName, Is.EqualTo("Updated"));
+            }
+        }
     }
 
     [CompositeIndex("FirstName", "LastName")]