/// <summary>
/// 后台扫描全表数据
/// </summary>
/// <typeparam name="TEntity"></typeparam>
/// <param name="dbContext">上下文</param>
/// <param name="tableCacheTimeSpan">tableCache过期时间</param>
private static void ScanTableBackground <TEntity>(DbContext dbContext, TimeSpan tableCacheTimeSpan) where TEntity : class
{
string scanKey = $"{DefaultValue.CacheKey_TableScanning}{dbContext.TableName}";
//1.判断正在扫描键是否存在，如果存在，则返回null，继续等待扫描任务完成
if (CacheStorageManager.IsExist(dbContext, scanKey))
{
return;
}
//2.如果没有扫描键，则执行后台扫描任务
Task.Run(() =>
{
//设置扫描键，标识当前正在进行扫描
CacheStorageManager.Put(dbContext, scanKey, 1, DefaultValue.SpanScaningKeyExpiredTime);
//对扫描任务加锁，防止多线程环境多次执行任务
lock (tableScaningLocker)
{
//双重校验当前缓存是否存在TableCache，防止多个进程在锁外等待，所释放后再次执行
if (CacheStorageManager.IsExist(dbContext, GetTableCacheKey(dbContext)))
{
return;
}
//如果过期时间为0，则取上下文的过期时间
TimeSpan timeSpan = tableCacheTimeSpan == TimeSpan.Zero ? dbContext.TableCacheExpiredTimeSpan : tableCacheTimeSpan;
//执行扫描全表任务，并将结果存入缓存中
var data = GetFullTableData <TEntity>(dbContext);
if (data != null)
{
CacheStorageManager.Put(dbContext, GetTableCacheKey(dbContext), data, dbContext.TableCacheExpiredTimeSpan);
}
}
//将扫描键移除，表示已经扫描完成
CacheStorageManager.Delete(dbContext, scanKey);
});
}
/// <summary>
/// 清空所有缓存
/// </summary>
internal static void FlushAllCache(DbContext dbContext)
{
if (CacheStorageManager.IsExist(dbContext, DefaultValue.GetQueryCacheKeysCacheKey(dbContext.DataBaseName), out HashSet <string> keys))
{
foreach (var item in keys)
{
CacheStorageManager.Delete(dbContext, item);
}
}
}
/// <summary>
/// 清空单个表相关的所有缓存
/// </summary>
/// <param name="dbContext"></param>
internal static void FlushTableCache(DbContext dbContext)
{
CacheStorageManager.Delete(dbContext, GetQueryCacheKey(dbContext));
}
