如何从Azure存储表中删除时间戳超过1天的所有实体？

Question

Azure storage tables all have a timestamp column. Based on documentation here the listed way to delete from a storage table is to select an entity then delete it.

Does anyone know how to delete any entity from a storage table based on a datetime comparison on the timestamp value using code?

EDIT:

Based on the advice given I wrote the following code. However, it throws a Bad Request exception on my table.ExecuteQuery(rangeQuery) call. Any advice?

    StorageCredentials creds = new StorageCredentials(logAccountName, logAccountKey);
    CloudStorageAccount account = new CloudStorageAccount(creds, useHttps: true);

    CloudTableClient client = account.CreateCloudTableClient();

    CloudTable table = client.GetTableReference(LogTable);

    TableQuery<CloudQuerySummary> rangeQuery = new TableQuery<CloudQuerySummary>()
        .Where(TableQuery.GenerateFilterCondition("Timestamp", QueryComparisons.LessThan
        , DateTime.Now.AddHours(- DateTime.Now.Hour).ToString()));


    TableOperation deleteOperation;
    // Loop through the results, displaying information about the entity.
    foreach (CloudQuerySummary entity in table.ExecuteQuery(rangeQuery))
    {
        deleteOperation = TableOperation.Delete(entity);

        table.Execute(deleteOperation);
    }

EDIT 2

Here is the final working code for anyone who chooses to copy/reference it.

public void DeleteLogsNotFromToday()
{
    StorageCredentials creds = new StorageCredentials(logAccountName, logAccountKey);
    CloudStorageAccount account = new CloudStorageAccount(creds, useHttps: true);

    CloudTableClient client = account.CreateCloudTableClient();

    CloudTable table = client.GetTableReference(LogTable);

    TableQuery<CloudQuerySummary> rangeQuery = new TableQuery<CloudQuerySummary>()
        .Where(TableQuery.GenerateFilterConditionForDate("Timestamp", QueryComparisons.LessThan
        , DateTime.Now.AddHours(-DateTime.Now.Hour)));

    try
    {

        TableOperation deleteOperation;
        // Loop through the results, displaying information about the entity.
        foreach (CloudQuerySummary entity in table.ExecuteQuery(rangeQuery))
        {
            deleteOperation = TableOperation.Delete(entity);

            table.Execute(deleteOperation);
        }
    }
    catch (Exception ex)
    {
        throw;
    }

}

Answer 1

You will have to do a partition scan to do that, as entities are only indexed on their PartitionKey and RowKey.

In the tutorial link you posted, look at the section Retrieve a range of entities in a partition . Once you get the entities you want to delete, you will then execute a table operation to delete them.

If you don't want to delete them one by one, you can create a batch delete operation (provided all entities to delete have the same partition key). The link above also instructs how to construct a batch operation.

Alternatively, if you do not want to do a table scan, you should store the date reference (for instance, storing the date in milliseconds as the RowKey) and then use that to filter the entities you need to delete based on a date-time comparison (something similar to THIS )

UPDATE: I think the problem is in this line: DateTime.Now.AddHours(- DateTime.Now.Hour).ToString()

As from the documentation :

The Timestamp property is a DateTime value that is maintained on the server side to record the time an entity was last modified

You are trying to compare a DateTime property with a String. I'm no C# expert, but that does not look to me as a valid comparison.

Answer 2

If you use Slazure this kind of job becomes easier, the following code should also work with the Light(free) edition.

using SysSurge.Slazure;
using SysSurge.Slazure.Linq;
using SysSurge.Slazure.Linq.QueryParser;

namespace TableOperations
{
    public class LogOperations 
    {
        public static void DeleteOldLogEntities()
        {
            // Get a reference to the table storage, example just uses the development storage
            dynamic storage = new QueryableStorage<DynEntity>("UseDevelopmentStorage=true");

            // Get a reference to the table named "LogTable"
            QueryableTable<DynEntity> logTable = storage.LogTable;
            var query = logTable.Where("Timestamp > @0", DateTime.UtcNow.AddDays(-1));

            // Delete all returned log entities
            foreach (var entity in query)
                logTable.Delete(entity.PartitionKey, entity.RowKey);
        }
    }
}

Full disclosure: I coded Slazure.