The SQL Persistence exposes an API to enable the creation of Saga Finders.
Usage
The API is exposed as an extension method on SynchronizedStorageSession and can be called as follows:
Microsoft SQL Server
On Microsoft SQL Server, the saga finder feature requires the JSON_VALUE function that is only available starting with SQL Server 2016.
class SqlServerSagaFinder :
ISagaFinder<MySagaData, MyMessage>
{
public Task<MySagaData> FindBy(MyMessage message, ISynchronizedStorageSession session, IReadOnlyContextBag context, CancellationToken cancellationToken = default)
{
return session.GetSagaData<MySagaData>(
context: context,
whereClause: "JSON_VALUE(Data,'$.PropertyPathInJson') = @propertyValue",
appendParameters: (builder, append) =>
{
var parameter = builder();
parameter.ParameterName = "propertyValue";
parameter.Value = message.PropertyValue;
append(parameter);
});
}
}
MySql
class MySqlSagaFinder :
ISagaFinder<MySagaData, MyMessage>
{
public Task<MySagaData> FindBy(MyMessage message, ISynchronizedStorageSession session, IReadOnlyContextBag context, CancellationToken cancellationToken = default)
{
return session.GetSagaData<MySagaData>(
context: context,
whereClause: "JSON_EXTRACT(Data,'$.PropertyPathInJson') = @propertyValue",
appendParameters: (builder, append) =>
{
var parameter = builder();
parameter.ParameterName = "propertyValue";
parameter.Value = message.PropertyValue;
append(parameter);
});
}
}
PostgreSql
class PostgreSqlSagaFinder :
ISagaFinder<MySagaData, MyMessage>
{
public Task<MySagaData> FindBy(MyMessage message, ISynchronizedStorageSession session, IReadOnlyContextBag context, CancellationToken cancellationToken = default)
{
return session.GetSagaData<MySagaData>(
context: context,
whereClause: @"""Data""->>'PropertyPathInJson' = @propertyValue",
appendParameters: (builder, append) =>
{
var parameter = builder();
parameter.ParameterName = "propertyValue";
parameter.Value = message.PropertyValue;
append(parameter);
});
}
}
Parameters
context
Used to ensure the concurrency metadata is stored in the current session.
whereClause
This text will be appended to a standard Saga select statement:
select
Id,
SagaTypeVersion,
Concurrency,
Metadata,
Data
from EndpointName_SagaName
with (updlock)
where 1 = 1
appendParameters
appendParameters allows DbParameters to be appended to the underlying DbCommand that will perform the query.
builder: calls through to DbCommand.CreateParameter to allow construction on a DbParameter.
append: calls through to DbParameterCollection.Add to add the parameter to the underlying DbCommand.
IContainSagaData Construction
Converting the returned information into an IContainSagaData will then be performed by the SQL Persister.
See also SQL Persistence Saga Finder Sample.