Best Practice in Deleting Azure Table Entities in ForEach Loop [duplicate]

Question

I have not had consistent results when deleting entities in an Azure table when the deletion occurs in a “foreach” loop. PartitionKey is unique.

Is there a best practice that folks can recommend?

I have left out Try..Catch statements for brevity.

Assuming:

var context = new FooContext(_storageAccount);

        var query = (from e in context.TableBar
                                where e.RowKey == rowKey
                                select e).AsTableServiceQuery();

Method #1

                foreach (var entity in query.Execute())
            {
                    // delete each entity
                    context.DeleteObject(entity);
                    context.SaveChanges();
            }

Method #2

            foreach (var entity in query.Execute())
            {
                    // delete each entity
                    context.DeleteObject(entity);
            }
            context.SaveChanges();

Method #3

            var bars = query.Execute();
            foreach (var bar in bars)
                context.DeleteObject(bar);
            context.SaveChanges();

Method #1 appears to delete most entities, but generally the last entity does not delete. It’s a valid entity.

Answer 1

If you already know the PartitionKey and RowKey of an entity you don't have to load it first. The fastest way is to use the CloudTable directly and a DynamicTableEntity like this:

var cloudTable = cloudTableClient.GetTableReference("TheTable");

var entity = new DynamicTableEntity(partitionKey, rowKey) { ETag = "*" };

cloudTable.Execute(TableOperation.Delete(entity));

If you want to delete a collection of entities which you don't know the RowKeys then you will need to load the entities first and use a Batch Operation to delete the entities. Also, you don't need to load all properties of the entities, we just need to know the RowKey so we can again use the same technique as above. For that we use a Projection Query

var batchOperation = new TableBatchOperation();

// We need to pass at least one property to project or else 
// all properties will be fetch in the operation
var projectionQuery = new TableQuery<DynamicTableEntity>()
    .Where(TableQuery.GenerateFilterCondition("PartitionKey", 
        QueryComparisons.Equal, "ThePartitionKey"))
    .Select(new string[] { "RowKey" });

foreach (var e in table.ExecuteQuery(projectionQuery))
    batchOperation.Delete(e);

table.ExecuteBatch(batchOperation);

A word of caution: a Batch Operation allows a maximum 100 entities in the batch which must share the same PartitionKey so you may need to split the entities into proper batches for this to work.