/// <summary>
/// Returns a new query where the result will be cached base on the <see cref="TimeSpan"/> parameter.
/// </summary>
/// <typeparam name="T">The type of entity being queried.</typeparam>
/// <param name="source">The source query.</param>
/// <param name="options">Options how to handle cached query results.</param>
/// <returns>A new query where the result set will be cached.</returns>
public static IQueryable <T> Cacheable <T>(this IQueryable <T> source, [NotParameterized] CacheableOptions options)
{
Check.NotNull(source, nameof(source));
Check.NotNull(options, nameof(options));
return
(source.Provider is EntityQueryProvider
? source.Provider.CreateQuery <T>(
Expression.Call(
instance: null,
method: CacheableMethodInfo.MakeGenericMethod(typeof(T)),
arg0: source.Expression,
arg1: Expression.Constant(options)))
: source);
}
private static Boolean ShouldResultBeCached <TResult>(TResult result, CacheableOptions options)
{
if (!options.CacheNullResult && result == null)
{
return(false);
}
if (result is IEnumerable)
{
var enumerable = result as IEnumerable;
return(enumerable.Any());
}
return(true);
}
private static async Task <TResult> ExecuteSingletonAsyncQuery <TResult>(
QueryContext queryContext,
Func <QueryContext, IAsyncEnumerable <TResult> > compiledQuery,
IDiagnosticsLogger <DbLoggerCategory.Query> logger,
Type contextType,
Func <object, Exception, string> logFormatter,
ICacheProvider cacheProvider,
object queryKey,
CacheableOptions options)
{
try
{
var asyncEnumerable = compiledQuery(queryContext);
using (var asyncEnumerator = asyncEnumerable.GetEnumerator())
{
await asyncEnumerator.MoveNext(queryContext.CancellationToken);
if (cacheProvider != null)
{
// add query result to cache
if (ShouldResultBeCached(asyncEnumerator.Current, options))
{
cacheProvider.SetCachedResult <TResult>(queryKey, asyncEnumerator.Current, options.TimeToLive);
}
logger.Logger.Log <object>(LogLevel.Debug, CacheableEventId.QueryResultCached, queryKey, null, logFormatter);
}
return(asyncEnumerator.Current);
}
}
catch (Exception exception)
{
logger.QueryIterationFailed(contextType, exception);
throw;
}
}