/// <summary>
/// Query feed item async
/// </summary>
/// <typeparam name="T">Feed entity</typeparam>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition key for feed</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="itemKey">Item key for feed item</param>
/// <returns>Feed entity in feed</returns>
public async Task <T> QueryFeedItemAsync <T>(FeedTable table, string partitionKey, string feedKey, string itemKey)
where T : FeedEntity, new()
{
this.ValidateQueryFeedItemParameters(table, partitionKey, feedKey, itemKey);
switch (table.StorageMode)
{
case StorageMode.PersistentOnly:
return(await this.persistentStore.QueryFeedItemAsync <T>(table, partitionKey, feedKey, itemKey));
case StorageMode.CacheOnly:
return(await this.cache.QueryFeedItemAsync <T>(table, partitionKey, feedKey, itemKey));
case StorageMode.Default:
T cacheEntity = await this.cache.QueryFeedItemAsync <T>(table, partitionKey, feedKey, itemKey);
if (this.IsCacheEntityNullOrInvalid(cacheEntity))
{
T persistentEntity = await this.persistentStore.QueryFeedItemAsync <T>(table, partitionKey, feedKey, itemKey);
return(persistentEntity);
}
return(cacheEntity);
default:
throw new NotSupportedException();
}
}
/// <summary>
/// Query feed async
/// </summary>
/// <typeparam name="T">Feed entity</typeparam>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition key for feed</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="cursor">Feed cursor</param>
/// <param name="limit">Feed count limit</param>
/// <returns>List of feed entities</returns>
public async Task <IList <T> > QueryFeedAsync <T>(
FeedTable table,
string partitionKey,
string feedKey,
string cursor,
int limit)
where T : FeedEntity, new()
{
string startRowKey = this.GetStartRowKeyForFeed(table, feedKey, cursor);
string endRowKey = this.GetEndRowKeyForFeed(table, feedKey);
string filterA = TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, partitionKey);
string filterB = TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.GreaterThan, startRowKey);
string filterC = TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.LessThan, endRowKey);
string filterAB = TableQuery.CombineFilters(filterA, TableOperators.And, filterB);
string filterABC = TableQuery.CombineFilters(filterAB, TableOperators.And, filterC);
TableQuery <DynamicTableEntity> query = new TableQuery <DynamicTableEntity>().Where(filterABC);
if (limit != int.MaxValue)
{
query = query.Take(limit);
}
CloudTable cloudTable = this.GetCloudTable(table);
var feedEntities = new List <T>();
TableContinuationToken token = null;
do
{
TableQuerySegment <DynamicTableEntity> segment = await cloudTable.ExecuteQuerySegmentedAsync <DynamicTableEntity>(query, token);
token = segment.ContinuationToken;
foreach (var item in segment)
{
T entity = this.GetEntityFromDynamicTableEntity <T>(item);
entity.PartitionKey = partitionKey;
entity.FeedKey = feedKey;
entity.ItemKey = this.GetItemKey(table, feedKey, item.RowKey);
entity.Cursor = entity.ItemKey;
feedEntities.Add(entity);
}
if (query.TakeCount != null)
{
if (feedEntities.Count == query.TakeCount.Value)
{
break;
}
}
}while (token != null);
return(feedEntities);
}
/// <summary>
/// Delete if exists operation on feed table
/// </summary>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition key for feed</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="itemKey">Item key for feed entity</param>
/// <returns>Table operation</returns>
public static Operation DeleteIfExists(FeedTable table, string partitionKey, string feedKey, string itemKey)
{
ValidateFeedTableParameters(table, partitionKey, feedKey, itemKey);
return(new Operation()
{
Table = table,
OperationType = OperationType.DeleteIfExists,
PartitionKey = partitionKey,
Key = feedKey,
ItemKey = itemKey
});
}
/// <summary>
/// Insert if not empty operation on feed table
/// </summary>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition key for feed</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="itemKey">Item key for feed entity</param>
/// <param name="entity">Feed entity</param>
/// <returns>Table operation</returns>
internal static Operation InsertIfNotEmpty(FeedTable table, string partitionKey, string feedKey, string itemKey, FeedEntity entity)
{
ValidateFeedTableParameters(table, partitionKey, feedKey, itemKey, entity);
return(new Operation()
{
Table = table,
OperationType = OperationType.InsertIfNotEmpty,
PartitionKey = partitionKey,
Key = feedKey,
ItemKey = itemKey,
Entity = entity.Clone()
});
}
/// <summary>
/// Replace operation on feed table
/// </summary>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition key for feed</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="itemKey">Item key for feed entity</param>
/// <param name="entity">Feed entity</param>
/// <returns>Table operation</returns>
public static Operation Replace(FeedTable table, string partitionKey, string feedKey, string itemKey, FeedEntity entity)
{
ValidateFeedTableParameters(table, partitionKey, feedKey, itemKey, entity);
return(new Operation()
{
Table = table,
OperationType = OperationType.Replace,
PartitionKey = partitionKey,
Key = feedKey,
ItemKey = itemKey,
Entity = entity.Clone()
});
}
/// <summary>
/// Delete operation on feed table
/// </summary>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition key for feed</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="itemKey">Item key for feed entity</param>
/// <param name="entity">Feed entity</param>
/// <returns>Table operation</returns>
public static Operation Delete(FeedTable table, string partitionKey, string feedKey, string itemKey, FeedEntity entity = null)
{
ValidateFeedTableParameters(table, partitionKey, feedKey, itemKey);
return(new Operation()
{
Table = table,
OperationType = OperationType.Delete,
PartitionKey = partitionKey,
Key = feedKey,
ItemKey = itemKey,
Entity = entity != null?entity.Clone() : null
});
}
/// <summary>
/// Query feed item async
/// </summary>
/// <typeparam name="T">Feed entity</typeparam>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition key for feed</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="itemKey">Item key for feed entity</param>
/// <returns>Feed entity result. Returns null if entity does not exist</returns>
public async Task <T> QueryFeedItemAsync <T>(FeedTable table, string partitionKey, string feedKey, string itemKey)
where T : FeedEntity, new()
{
string rowKey = this.GetRowKey(table, feedKey, itemKey);
T entity = await this.QueryTableEntity <T>(table, partitionKey, rowKey);
if (entity == null)
{
return(null);
}
entity.FeedKey = feedKey;
entity.ItemKey = itemKey;
entity.Cursor = entity.ItemKey;
return(entity);
}
/// <summary>
/// Query feed async
/// </summary>
/// <typeparam name="T">Feed entity</typeparam>
/// <param name="table">Feed table</param>
/// <param name="partitionKey">Partition for entity</param>
/// <param name="feedKey">Key for feed</param>
/// <param name="cursor">Feed cursor</param>
/// <param name="limit">Feed count limit</param>
/// <returns>List of feed entities</returns>
public async Task <IList <T> > QueryFeedAsync <T>(
FeedTable table,
string partitionKey,
string feedKey,
string cursor,
int limit)
where T : FeedEntity, new()
{
this.ValidateQueryFeedParameters(table, partitionKey, feedKey, limit);
switch (table.StorageMode)
{
case StorageMode.PersistentOnly:
return(await this.persistentStore.QueryFeedAsync <T>(table, partitionKey, feedKey, cursor, limit));
case StorageMode.CacheOnly:
return(await this.cache.QueryFeedAsync <T>(table, partitionKey, feedKey, cursor, limit));
case StorageMode.Default:
IList <T> cacheEntities = await this.cache.QueryFeedAsync <T>(table, partitionKey, feedKey, cursor, limit);
IList <T> invalidCacheEntities = cacheEntities.Where(e => this.IsCacheEntityNullOrInvalid(e)).ToList();
IEnumerable <Task <T> > persistentInvalidEntitiesTasks = null;
if (invalidCacheEntities.Count > 0)
{
persistentInvalidEntitiesTasks = from entity in invalidCacheEntities select this.persistentStore.QueryFeedItemAsync <T>(table, partitionKey, feedKey, entity.ItemKey);
}
IList <T> persistentEntities = new List <T>();
if (cacheEntities.Count < limit)
{
string continuationCursor = cacheEntities.Count == 0 ? cursor : cacheEntities.Last().ItemKey;
// We add count of invalid cache entities to be conservative in case all the invalid cache entities are null
// We add one more to the limit so there is at least item in the cache when the client queries with last item key as cursor
// If there are no items in the cache for a query, the entities in persistent store is not cached since we don't know the
// the range of the items and whether it continues from items in the cache.
int continuationLimit = limit - cacheEntities.Count;
if (int.MaxValue - continuationLimit < invalidCacheEntities.Count + 1)
{
continuationLimit = int.MaxValue;
}
else
{
continuationLimit += invalidCacheEntities.Count + 1;
}
persistentEntities = await this.persistentStore.QueryFeedAsync <T>(table, partitionKey, feedKey, continuationCursor, continuationLimit);
}
List <T> entities = new List <T>();
List <Operation> cachingOperations = new List <Operation>();
T[] persistentInvalidEntities = null;
if (persistentInvalidEntitiesTasks != null)
{
persistentInvalidEntities = await Task.WhenAll(persistentInvalidEntitiesTasks.ToArray());
}
int persistentInvalidEntityIndex = 0;
foreach (T cacheEntity in cacheEntities)
{
if (this.IsCacheEntityNullOrInvalid(cacheEntity))
{
T invalidPersistentEntity = persistentInvalidEntities[persistentInvalidEntityIndex++];
if (invalidPersistentEntity != null)
{
entities.Add(invalidPersistentEntity);
}
Operation cachingOperation = this.GetFeedCachingOperation(table, partitionKey, feedKey, cacheEntity.ItemKey, cacheEntity, invalidPersistentEntity, false);
if (cachingOperation != null)
{
cachingOperations.Add(cachingOperation);
}
}
else
{
entities.Add(cacheEntity);
}
}
foreach (T persistentEntity in persistentEntities)
{
entities.Add(persistentEntity);
// Add caching operations only if the persistent feed items are continuation
// of items retrieved from cache or if cursor is null (starting of the feed)
if (cacheEntities.Count > 0 || cursor == null)
{
// The cache could evict the entire feed before we run the caching operations.
// If the cache already has feed items, the eviction combined with the caching operations
// can violate the feed cache invariant.
// Hence, we need to make sure the the feed is not empty
// when newer items are added to the cache.
// We don't need to make this check if the cursor is null and there are
// no items in the cache to start with.
bool checkIfNotEmpty = cacheEntities.Count != 0;
Operation cachingOperation = this.GetFeedCachingOperation(table, partitionKey, feedKey, persistentEntity.ItemKey, null, persistentEntity, checkIfNotEmpty);
cachingOperations.Add(cachingOperation);
}
}
await this.ExecuteCachingOperationsAsync(cachingOperations);
return(entities.Take(limit).ToList());
default:
throw new NotSupportedException();
}
}