How to execute an Azure table storage query async? client version 4.0.1
Want to execute queries Async on Azure Storage Client Version 4.0.1
There is NO method ExecuteQueryAsync()..
I am missing something? Should we continue to use the ExecuteQuerySegmentedAsync still? Thanks.
I end up making an extension method to use ExecuteQuerySegmentedAsync. I am not sure whether this solution is optimal, if anybody has any comment please don’t hesitate.
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;
}
When table query contains take clause specified solution will return more items than requested by query. Small change of while expression will solve that problem.
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;
}
EDITED: Thanks to a suggestion from PaulG, corrected the issue with result count when query contains take clause and ExecuteQuerySegmentedAsync
returns items in several passes.
This is in addition on to @JoseCh.
's answer.
Here is an extension method which allows you to specify an EntityResolver:
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;
}
}
It can be used if you only want to return the result set of a single column in storage:
// 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()