Querying Azure Table Storage - compare using a static array of values

Question

I need to modify and existing Azure Table Storage query, assuming i is an integer query retrieves latest report:

string rowCompare = String.Format(CommonDefs.inverseTimeStampRowKeyFormat, DateTime.MaxValue.Ticks - DateTime.UtcNow.Ticks);
var result = (from er in this.serviceContext.EntityReportsTable
                           where er.PartitionKey.Equals(i.ToString(), StringComparison.OrdinalIgnoreCase) && er.RowKey.CompareTo(rowCompare) > 0
                           select er).Take(1)).FirstOrDefault();

I need to modify it to retrieve latest reports for several known entities, replacing single integer i with array of integers - like int[]{1, 6, 10}.

Apart from running existing query sequentially for the each parameter in array, is there a way to do it in one query? Like IN clause in Sql?

Answer 1

You can use the lastest version of the Azure Storage Client Library this is the complete pseudo code for your task:

var rowCompare = String.Format("{0}", DateTime.MaxValue.Ticks - DateTime.UtcNow.Ticks);
var items = new []{"1", "6", "10"};

var filters =
    items.Select(key => TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, key)).ToArray();

var combine =
    filters.Length > 0
        ? filters[0]
        : null;

for (var k = 0; k < filters.Length; k++)
    combine = TableQuery.CombineFilters(combine, TableOperators.Or, filters[k]);

var final = TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.GreaterThan, rowCompare);
if (!string.IsNullOrEmpty(combine))
    final = TableQuery.CombineFilters(final, TableOperators.And, combine);

var query = new TableQuery<EntityReport>().Where(final);

var client = CloudStorageAccount.DevelopmentStorageAccount.CreateCloudTableClient();
var table = client.GetTableReference("EntityReports");
var result = table.ExecuteQuery(query);

Answer 2

Azure Table Storage does not support IN clause like SQL. However instead of doing a query sequentially, you could fire queries in parallel and compare the result. For example look at the pseudo code below:

        List<Task<T>> tasks = new List<Task<T>>();
        foreach (var i in integerArray)
        {
            tasks.Add(Task.Factory.StartNew<T>(() => {
                string rowCompare = String.Format(CommonDefs.inverseTimeStampRowKeyFormat, DateTime.MaxValue.Ticks - DateTime.UtcNow.Ticks);
                var result = (from er in this.serviceContext.EntityReportsTable
                                           where er.PartitionKey.Equals(i.ToString(), StringComparison.OrdinalIgnoreCase) && er.RowKey.CompareTo(rowCompare) > 0
                                           select er).Take(1)).FirstOrDefault();
            }));
        }
        Task.WaitAll(tasks.ToArray());
        foreach (var task in tasks)
        {
            var queryResult = task.Result;
            //Work on the query result
        }