想要在Azure存储客户端版本4.0.1上异步执行查询?
很遗憾,没有ExecuteQueryAsync()方法。
我是否漏掉了什么?我们是否继续使用ExecuteQuerySegmentedAsync?谢谢。
想要在Azure存储客户端版本4.0.1上异步执行查询?
很遗憾,没有ExecuteQueryAsync()方法。
我是否漏掉了什么?我们是否继续使用ExecuteQuerySegmentedAsync?谢谢。
我最终创建了一个扩展方法来使用ExecuteQuerySegmentedAsync。我不确定这个解决方案是否是最优的,如果有任何评论,请不要犹豫。
public static async Task<IList<T>> ExecuteQueryAsync<T>(this CloudTable table, TableQuery<T> query, CancellationToken ct = default(CancellationToken), Action<IList<T>> onProgress = null) where T : ITableEntity, new()
{
var items = new List<T>();
TableContinuationToken token = null;
do
{
TableQuerySegment<T> seg = await table.ExecuteQuerySegmentedAsync<T>(query, token);
token = seg.ContinuationToken;
items.AddRange(seg);
if (onProgress != null) onProgress(items);
} while (token != null && !ct.IsCancellationRequested);
return items;
}
ExecuteQuerySegmentedAsync
并组合每个段的结果)。你的代码看起来很好。我唯一的建议是,如果可能的话,通过使用接受整数的构造函数来预先分配足够大以容纳大多数实体的items
列表的大小。这将减少所需的调整大小的数量。 - Mike Fisherct
(CancellationToken)传递到 ExecuteQuerySegmentedAsync
中,因为这个扩展在其他地方都没有使用它。我认为 @Jose Ch. 忘记添加它了,我试图编辑帖子,因为 ct 小于 6 个字符 :< - Rutix当表查询包含指定的take子句时,解决方案将返回比查询请求的更多的项目。稍微改变while表达式即可解决这个问题。
public static async Task<IList<T>> ExecuteQueryAsync<T>(this CloudTable table, TableQuery<T> query, CancellationToken ct = default(CancellationToken), Action<IList<T>> onProgress = null) where T : ITableEntity, new()
{
var runningQuery = new TableQuery<T>()
{
FilterString = query.FilterString,
SelectColumns = query.SelectColumns
};
var items = new List<T>();
TableContinuationToken token = null;
do
{
runningQuery.TakeCount = query.TakeCount - items.Count;
TableQuerySegment<T> seg = await table.ExecuteQuerySegmentedAsync<T>(runningQuery, token);
token = seg.ContinuationToken;
items.AddRange(seg);
if (onProgress != null) onProgress(items);
} while (token != null && !ct.IsCancellationRequested && (query.TakeCount == null || items.Count < query.TakeCount.Value));
return items;
}
编辑:由于PaulG的建议,纠正了当查询包含take子句且ExecuteQuerySegmentedAsync
返回多次时结果计数的问题。
public static async Task<IList<TResult>> ExecuteQueryAsync<T, TResult>(this CloudTable table, TableQuery query, EntityResolver<TResult> resolver, Action<IList<TResult>> onProgress = null, CancellationToken cancelToken = default(CancellationToken))
where T : ITableEntity, new()
{
var items = new List<TResult>();
TableContinuationToken token = null;
do
{
TableQuerySegment<TResult> seg = await table.ExecuteQuerySegmentedAsync(query: query, resolver: resolver, token: new TableContinuationToken(), cancellationToken: cancelToken).ConfigureAwait(false);
token = seg.ContinuationToken;
items.AddRange(seg);
onProgress?.Invoke(items);
}
while (token != null && !cancelToken.IsCancellationRequested);
return items;
}
}
如果您只想返回存储中单个列的结果集,则可以使用它:
// maps to a column name in storage
string propertyName = nameof(example.Category);
// Define the query, and select only the Category property.
var projectionQuery = new TableQuery().Select(new string[] { propertyName });
// Define an entity resolver to work with the entity after retrieval.
EntityResolver<string> resolver = (pk, rk, ts, props, etag) => props.ContainsKey(propertyName) ? props[propertyName].StringValue : null;
var categories = (await someTable.ExecuteQueryAsync<DynamicTableEntity, string>(query: projectionQuery, resolver: resolver).ConfigureAwait(false)).ToList()