Sql Storage

Storage is configurable. By default, journal files and snapshots are written to the file system. Using Sql Storage, the journal can be stored in a relational database, allowing you to take advantage of existing infrastructure and keep your DBA’s and sysadmins calm. Also, the journal can be queried/manipulated using regular SQL.

Sql storage is flexible and extensible. You can supply custom statements for initializing, reading and writing entries. For custom behavior, create a subclass of SqlCommandStore or CommandStore.

The default table has these columns:

Name Type Description
Id ulong The unique sequential id of the journal entry
Created DateTime When the command was executed
Type String The type name of the command executed
Data Binary The serialized command

To enable sql storage set the storage type for journaling to Sql:

var config = new EngineConfiguration();
config.JournalStorage = StorageType.Sql;
var engine = Engine.For<MyDb>(config);

The default settings assume a connection string entry in the application configuration file named ‘origo’:

<connectionString name="origo"
  connectionString="Data Source=.;Initial Catalog=freedb;Integrated Security=True"

Here are the default settings. Simply assign new values to customize. The ConnectionString property can be assigned either a connection string name in the application configuration file or an actual connection string.

config.SqlSettings.TableName = "OrigoJournal";
config.SqlSettings.ConnectionString = "origo";
config.SqlSettings.ProviderName = "System.Data.SqlClient";
config.SqlSettings.SkipInit = false;
var engine = Engine.For<MyDb>(config);

Custom SQL statements

Each supported provider has an associated SqlStatements object. The default is MsSqlStatements which works with Microsoft Sql Server 2008 and above. To customize, there are a few alternative paths:

  • Create an instance of SqlStatements and assign each statement.
  • Create an instance of a sub class, for example MsSqlStatements, and modify existing statements.
  • Set a flag causing the InitStore statement to be skipped.

To apply custom statements, assign to the SqlSettings.Statements property. Example code:

var config = new EngineConfiguration();
var settings = config.SqlSettings;
settings.SkipInit = true;
settings.Statements = new SqlStatements
  AppendEntry = "EXEC uspAppendEntry @id, @created, @type, @data",
  ReadEntries = "SELECT * FROM {0} WHERE id >= @id ORDER BY id"

Note the {0} placeholder. String.Format will be applied to the statements passing a single argument of SqlSettings.TableName.

Supported providers

The ProviderName must be one the following supported providers. Otherwise a custom provider needs to be configured. See Custom Providers below.

  • System.Data.SqlClient - has been tested with Sql Server 2008 and above
  • System.Data.OleDb - not yet tested so probably not operational.
  • System.Data.SqlServerCe.4.0 - will use MsSqlStatements but has not been tested

Custom Providers

The Sql Storage implementation is generic and relies on ADO.NET Provider factories to supply vendor specific connections, commands and parameter objects. Here’s some reading on the topic: https://msdn.microsoft.com/en-us/library/ms379620%28VS.80%29.aspx

Unfortunately, sql differs across vendors so to be able to use a custom provider, a SqlStatements object with compatible statements needs to be associated with the provider name. A fictive example:

//Note, this is just an example
//the NpgSqlStatements class does not exist!
SqlCommandStore.ProviderStatements["NpgSql"] = new NpgSqlStatements();

Customizing behavior

Derive from SqlCommandStore or CommandStore and override one or more methods. Then register the custom store:

var config = new EngineConfiguration();
config.SetCommandStoreFactory(cfg => new MySqlCommandStore(cfg));
var engine = Engine.For<MyModel>(config);