Stateful Query Provider

IQueryPersistenceService in assembly SanteDB.Core.Api version 2.1.151.0

Summary

Defines a service which can store the results of a query for later retrieval

Description

When implementing query on a shared infrastructure such as the SanteDB iCDR or dCDR, it is important that consistent result sets be returned. This is important not only for user interfaces, but is vital to consistent synchronization across devices.

There are several reasons we keep stateful query result sets in SanteDB:

• User interfaces will have consistent pages, so results don't magically "appear" between paging results

• Synchronization processes have a consistent paging result set as they download data

• The heavy initial query is done only once and results are merely accessed afterwards

Implementers of this service should ensure that whatever technology they are using to store queries have the capability of expiration (i.e. queries are not stateful indefinitely), support the rapid read and update of result sets, and are cabable of being aborted/abandoned.

Operations

Operation	Response/Return	Input/Parameter	Description
FindQueryId	Guid	Object queryTag	Locate the stateful query identifier using the tag which was attached to the query
RegisterQuerySet	Boolean	Guid queryId IEnumerable<Guid> results Object tag Int32 totalResults	Registers a new query result set with the stateful query provider
IsRegistered	Boolean	Guid queryId	Returns true if the query identifier has been registered
GetQueryResults	IEnumerable<Guid>	Guid queryId Int32 offset Int32 count	Retrieves the result keys located between and + in the stateful query provider
GetQueryTag	Object	Guid queryId	Retrieves the query tag stored when the query was registered, for the specified
QueryResultTotalQuantity	Int64	Guid queryId	Count the number of query results which have been registered for
AddResults	void	Guid queryId IEnumerable<Guid> results Int32 totalResults	Adds more results to an already registered stateful query
SetQueryTag	void	Guid queryId Object value	Adds or changes the query tag on to

Implementations

Memory-Based Query Persistence Service - (SanteDB.Caching.Memory)

An implementation of the IQueryPersistenceService which uses in-process memory to store query result sets

Description

This implementation of the query persistence service uses the MemoryCache implementation to store stateful query results (for consistent pagination) for a period of time in transient place.

Service Registration

...
<section xsi:type="ApplicationServiceContextConfigurationSection" threadPoolSize="4">
	<serviceProviders>
		...
		<add type="SanteDB.Caching.Memory.MemoryQueryPersistenceService, SanteDB.Caching.Memory, Version=2.1.151.0, Culture=neutral, PublicKeyToken=null" />
		...
	</serviceProviders>

REDIS Query Persistence Service - (SanteDB.Caching.Redis)

An implementation of the IQueryPersistenceService which usees REDIS for its stateful result set

Description

This persistence service uses REDIS list values to store the UUIDs representing the query executed on the SanteDB server. The data is stored in database 2 of the REDIS server.

Service Registration

...
<section xsi:type="ApplicationServiceContextConfigurationSection" threadPoolSize="4">
	<serviceProviders>
		...
		<add type="SanteDB.Caching.Redis.RedisQueryPersistenceService, SanteDB.Caching.Redis, Version=2.1.151.0, Culture=neutral, PublicKeyToken=null" />
		...
	</serviceProviders>

Example Implementation

/// Example Implementation
using SanteDB.Core.Services;
/// Other usings here
public class MyQueryPersistenceService : SanteDB.Core.Services.IQueryPersistenceService { 
	public String ServiceName => "My own IQueryPersistenceService service";
	/// <summary>
	/// Locate the stateful query identifier using the tag which was attached to the query
	/// </summary>
	public Guid FindQueryId(Object queryTag){
		throw new System.NotImplementedException();
	}
	/// <summary>
	/// Registers a new query result set with the stateful query provider
	/// </summary>
	public Boolean RegisterQuerySet(Guid queryId,IEnumerable<Guid> results,Object tag,Int32 totalResults){
		throw new System.NotImplementedException();
	}
	/// <summary>
	/// Returns true if the query identifier has been registered
	/// </summary>
	public Boolean IsRegistered(Guid queryId){
		throw new System.NotImplementedException();
	}
	/// <summary>
	/// Retrieves the result keys located between  and + in the stateful query provider
	/// </summary>
	public IEnumerable<Guid> GetQueryResults(Guid queryId,Int32 offset,Int32 count){
		throw new System.NotImplementedException();
	}
	/// <summary>
	/// Retrieves the query tag stored when the query was registered, for the specified
	/// </summary>
	public Object GetQueryTag(Guid queryId){
		throw new System.NotImplementedException();
	}
	/// <summary>
	/// Count the number of query results which have been registered for
	/// </summary>
	public Int64 QueryResultTotalQuantity(Guid queryId){
		throw new System.NotImplementedException();
	}
	/// <summary>
	/// Adds more results to an already registered stateful query
	/// </summary>
	public void AddResults(Guid queryId,IEnumerable<Guid> results,Int32 totalResults){
		throw new System.NotImplementedException();
	}
	/// <summary>
	/// Adds or changes the query tag on  to
	/// </summary>
	public void SetQueryTag(Guid queryId,Object value){
		throw new System.NotImplementedException();
	}
}

References

• IQueryPersistenceService C# Documentation

• MemoryQueryPersistenceService C# Documentation

• RedisQueryPersistenceService C# Documentation