Stored saga json state can cause custom tooling parsing issues on SQL Server

src/SqlPersistence.PersistenceTests/When_updating_saga_with_smaller_state.cs

@@ -0,0 +1,93 @@
+namespace NServiceBus.PersistenceTesting.Sagas
+{
+    using System;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using NUnit.Framework;
+
+    public class When_updating_saga_with_smaller_state : SagaPersisterTests
+    {
+        [Test]
+        public async Task It_should_truncate_the_stored_state()
+        {
+            // When updating an existing saga where the serialized state is smaller in length than the previous the column value should not have any left over data from the previous value.
+            // The deserializer ignores any trailing 
+
+            var sqlVariant = (SqlTestVariant)param.Values[0];
+
+            if (sqlVariant.Dialect is not SqlDialect.MsSqlServer)
+            {
+                Assert.Ignore("Only relevant for SQL Server");
+                return; // Satisfy compiler
+            }
+
+            var sagaData = new SagaWithCorrelationPropertyData
+            {
+                CorrelatedProperty = Guid.NewGuid().ToString(),
+                Payload = "very long state"
+            };
+
+            await SaveSaga(sagaData);
+
+            SagaWithCorrelationPropertyData retrieved;
+            var context = configuration.GetContextBagForSagaStorage();
+            var persister = configuration.SagaStorage;
+
+            using (var completeSession = configuration.CreateStorageSession())
+            {
+                await completeSession.Open(context);
+
+                retrieved = await persister.Get<SagaWithCorrelationPropertyData>(nameof(sagaData.CorrelatedProperty), sagaData.CorrelatedProperty, completeSession, context);
+
+                retrieved.Payload = "short";
+
+                await persister.Update(retrieved, completeSession, context);
+                await completeSession.CompleteAsync();
+            }
+
+            var retrieved2 = await GetById<SagaWithCorrelationPropertyData>(sagaData.Id);
+
+            Assert.LessOrEqual(retrieved.Payload, sagaData.Payload); // No real need, but here to prevent accidental updates
+            Assert.AreEqual(retrieved.Payload, retrieved2.Payload);
+
+            await using var con = sqlVariant.Open();
+            await con.OpenAsync();
+            var cmd = con.CreateCommand();
+            cmd.CommandText = $"SELECT Data FROM [PersistenceTests_SWCP] WHERE Id = '{retrieved.Id}'";
+            var data = (string)await cmd.ExecuteScalarAsync();
+
+            // Payload should only have a single closing bracket, if there are more that means there is trailing data
+            var countClosingBrackets = data.ToCharArray().Count(x => x == '}');
+
+            Assert.AreEqual(1, countClosingBrackets);
+        }
+
+        public class SagaWithCorrelationProperty : Saga<SagaWithCorrelationPropertyData>, IAmStartedByMessages<StartMessage>
+        {
+            public Task Handle(StartMessage message, IMessageHandlerContext context)
+            {
+                throw new NotImplementedException();
+            }
+
+            protected override void ConfigureHowToFindSaga(SagaPropertyMapper<SagaWithCorrelationPropertyData> mapper)
+            {
+                mapper.ConfigureMapping<StartMessage>(msg => msg.SomeId).ToSaga(saga => saga.CorrelatedProperty);
+            }
+        }
+
+        public class SagaWithCorrelationPropertyData : ContainSagaData
+        {
+            public string CorrelatedProperty { get; set; }
+            public string Payload { get; set; }
+        }
+
+        public class StartMessage
+        {
+            public string SomeId { get; set; }
+        }
+
+        public When_updating_saga_with_smaller_state(TestVariant param) : base(param)
+        {
+        }
+    }
+}

src/SqlPersistence/CommandWrapper.cs

@@ -64,12 +64,14 @@ public Task<int> ExecuteNonQueryAsync(CancellationToken cancellationToken = defa
 
     public Task<DbDataReader> ExecuteReaderAsync(CancellationToken cancellationToken = default)
     {
+        dialect.OptimizeForReads(command);
         return command.ExecuteReaderAsync(cancellationToken);
     }
 
     public Task<DbDataReader> ExecuteReaderAsync(CommandBehavior behavior, CancellationToken cancellationToken = default)
     {
         var resultingBehavior = dialect.ModifyBehavior(command.Connection, behavior);
+        dialect.OptimizeForReads(command);
         return command.ExecuteReaderAsync(resultingBehavior, cancellationToken);
     }
 

src/SqlPersistence/Config/SqlDialect.cs

@@ -62,5 +62,9 @@ internal virtual void ValidateTablePrefix(string tablePrefix)
         }
 
         internal abstract object GetCustomDialectDiagnosticsInfo();
+
+        internal virtual void OptimizeForReads(DbCommand command)
+        {
+        }
     }
 }

src/SqlPersistence/Config/SqlDialect_MsSqlServer.cs

@@ -34,18 +34,7 @@ internal override void SetParameterValue(DbParameter parameter, object value)
                 if (value is ArraySegment<char> charSegment)
                 {
                     parameter.Value = charSegment.Array;
-
-                    // Set to 4000 or -1 to improve query execution plan reuse
-                    // Must be set when exceeding 4000 characters for nvarchar(max)  https://stackoverflow.com/a/973269/199551
-                    parameter.Size = charSegment.Count > 4000 ? -1 : 4000;
-                }
-                else if (value is string stringValue)
-                {
-                    parameter.Value = stringValue;
-
-                    // Set to 4000 or -1 to improve query execution plan reuse
-                    // Must be set when exceeding 4000 characters for nvarchar(max)  https://stackoverflow.com/a/973269/199551
-                    parameter.Size = stringValue.Length > 4000 ? -1 : 4000;
+                    parameter.Size = charSegment.Count;
                 }
                 else
                 {
@@ -84,9 +73,29 @@ internal override object GetCustomDialectDiagnosticsInfo()
                 };
             }
 
+            internal override void OptimizeForReads(DbCommand command)
+            {
+                foreach (DbParameter parameter in command.Parameters)
+                {
+                    if (parameter.Value is ArraySegment<char> charSegment)
+                    {
+                        // Set to 4000 or -1 to improve query execution plan reuse
+                        // Must be set when exceeding 4000 characters for nvarchar(max)  https://stackoverflow.com/a/973269/199551
+                        parameter.Size = charSegment.Count > 4000 ? -1 : 4000;
+                    }
+                    else if (parameter.Value is string stringValue)
+                    {
+                        // Set to 4000 or -1 to improve query execution plan reuse
+                        // Must be set when exceeding 4000 characters for nvarchar(max)  https://stackoverflow.com/a/973269/199551
+                        parameter.Size = stringValue.Length > 4000 ? -1 : 4000;
+                    }
+                }
+            }
+
             internal string Schema { get; set; }
             bool hasConnectionBeenInspectedForEncryption;
             bool isConnectionEncrypted;
         }
+
     }
 }