/// <summary>
/// 尝试获取指定表达式的缓存。
/// </summary>
/// <param name="expression"></param>
/// <param name="context"></param>
/// <param name="creator">当缓存不存在时，创建缓存数据的函数。</param>
/// <returns></returns>
Delegate IQueryCache.TryGetDelegate(Expression expression, QueryCacheContext context, Func <LambdaExpression> creator)
{
var section = ConfigurationUnity.GetSection <TranslatorConfigurationSection>();
var option = section == null ? TranslateOptions.Default : section.Options;
var result = CacheableChecker.Check(expression);
if (!result.Required ||
(result.Enabled == null && (context.Enabled == false || (context.Enabled == null && !option.CacheParsing))) ||
result.Enabled == false)
{
return(creator().Compile());
}
var generator = _serviceProvider.TryGetService <IQueryCacheKeyGenerator>(() => ExpressionKeyGenerator.Instance);
var cacheKey = _serviceProvider.GetCacheKey(generator.Generate(expression, "Trans"));
Tracer.Debug($"QueryCache access to '{cacheKey}'");
var cacheMgr = _serviceProvider.TryGetService <IMemoryCacheManager>(() => MemoryCacheManager.Instance);
return(cacheMgr.TryGet(cacheKey, () =>
{
var lambdaExp = creator() as LambdaExpression;
var segment = SegmentFinder.Find(expression);
if (segment != null)
{
//将表达式内的 Segment 替换成参数
var segParExp = Expression.Parameter(typeof(IDataSegment), "g");
var newExp = SegmentReplacer.Repalce(lambdaExp.Body, segParExp);
var parameters = new List <ParameterExpression>(lambdaExp.Parameters);
parameters.Insert(1, segParExp);
lambdaExp = Expression.Lambda(newExp, parameters.ToArray());
}
return lambdaExp.Compile();
},
() => new RelativeTime(GetExpire(result, option, context))));
}
private TimeSpan GetExpire(CacheableCheckResult result, TranslateOptions option, QueryCacheContext cacheOpt)
{
if (result.Expired != null)
{
return(result.Expired.Value);
}
else if (cacheOpt.Times != null)
{
return(cacheOpt.Times.Value);
}
return(option.CacheExecutionTimes);
}