Querying Windows Azure Table Storage with multiple

问题:

I'm trying to query a table in Windows Azure storage and was initially using the TableQuery.CombineFilters in the TableQuery<RecordEntity>().Where function as follows:

TableQuery.CombineFilters(
    TableQuery.GenerateFilterCondition("PartitionKey",   QueryComparisons.GreaterThanOrEqual, lowDate),
    TableOperators.And,
    TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.LessThanOrEqual, lowDate),
    TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, entityId)
));

Unfortunately CombineFilters only allows 2 query criteria max. So I'm currently doing this:

var tableQuery = new TableQuery<RecordRowEntity>()
            .Where(TableQuery.CombineFilters("PartitionKey", string.Format("(PartitionKey ge '{0}') and (PartitionKey le '{1}') and (RowKey eq '{2}')", low, high, entityId));

Is there any other way of doing it. Am conerned that the way I'm doing it at present is vulnerable to changes in the way the Azure Api works.

回答1:

A combined filter can then be combined with another filter, repeating as many times as necessary. See the example "Sample – Query all entities with a PartitionKey=”SamplePK” and RowKey greater than or equal to “5”" at http://blogs.msdn.com/b/windowsazurestorage/archive/2012/11/06/windows-azure-storage-client-library-2-0-tables-deep-dive.aspx.

string pkFilter = TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, "samplePK");


string rkLowerFilter = TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.GreaterThanOrEqual, "5");

string rkUpperFilter = TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.LessThan, "10");

// Note CombineFilters has the effect of "([Expression1]) Operator (Expression2]), as such passing in a complex expression will result in a logical grouping.
string combinedRowKeyFilter = TableQuery.CombineFilters(rkLowerFilter, TableOperators.And, rkUpperFilter);

string combinedFilter = TableQuery.CombineFilters(pkFilter, TableOperators.And, combinedRowKeyFilter);

// OR 
string combinedFilter = string.Format("({0}) {1} ({2}) {3} ({4})", pkFilter, TableOperators.And, rkLowerFilter, TableOperators.And, rkUpperFilter);
TableQuery query = new TableQuery().Where(combinedFilter);

回答2:

This is what I am using as a quick check for the range of uploaded records.

        .....

        Dictionary<int, string[]> retrievedRecords = new Dictionary<int, string[]>();
        int i = 0;

        StorageCredentials creds = new StorageCredentials(accountName, accountKey); // table storage name, Azure provided KEY1 string
        CloudStorageAccount storageAccount = new CloudStorageAccount(creds, useHttps: true);
        CloudTableClient tableClient = storageAccount.CreateCloudTableClient();

        CloudTable table = tableClient.GetTableReference(tableName); // your table name

        // filters
        string filter1 = TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, partitionName); // partitionName i.e.: "myTablePartition1"
        string filter2 = TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.GreaterThanOrEqual, recordStart); // recordStart i.e.: "123"
        string filter3 = TableQuery.GenerateFilterCondition("RowKey", QueryComparisons.LessThan, recordEnd); // recordEnd i.e.: "567"

        string filterRange = TableQuery.CombineFilters(filter2, TableOperators.And, filter3);


        // query.
        TableQuery<CustomerEntity> rangeQuery = new TableQuery<CustomerEntity>().Where(

            TableQuery.CombineFilters(filter1, TableOperators.And, filterRange)
        );

        // Loop & store
        foreach (CustomerEntity entityT in table.ExecuteQuery(rangeQuery))
        {
            string PartitionKey = entityT.PartitionKey;
            string RowKey = entityT.RowKey;
            string col1 = entityT.col1;
            string col2  = entityT.col2;
            string col3  = entityT.col3;
            string col4  = entityT.col4;
            string col5  = entityT.col5;
            string col6  = entityT.col6;

            string[] row = new string[] { PartitionKey, RowKey, col1 , col2, col3, col4, col5, col6 };
            retrievedRecords.Add(i, row);

            i++;
        }

        return retrievedRecords;

// function end or else.....
....