使用表达式查询 Azure 表存储

Question

I'm looking to query table storage by passing an expression into my repository instead of a TableQuery, i'm aiming for this:

public async Task<IEnumerable<FiltersEntity>> Get(Expression<Func<FiltersEntity, bool>> query)
{  
    var table = _tableStorageConnector.CreateTableIfNotExists(_tableName);


    return await table.CreateQuery<FiltersEntity>().Where(query).ToList();
}

Ideal usage:

    var data = await _filterRepository.Get(x => x.PartitionKey.Equals("examplepartitionkey"));

I can't see any methods on CreateQuery or CreateQuery which accept an expression, only text.

I've also looked to see if I can convert the expression to filter text such as PartitionKey eq examplepartitionkey , but no luck.

Can someone please help me query azure table storage via expression?

The SDK i'm using is Microsoft.Azure.Cosmos.Table v1.0.7.0;

Answer 1

Assuming using the Cosmos table driver against Azure Table Storage, you should be able to something along the lines of

public async Task<IEnumerable<MyTable>> MyQuery(Expression<Func<MyTable, bool>> predicate)
{
    var tableClient = new CloudTableClient(
        new Uri("..."),
        new StorageCredentials(".."));

    var table = tableClient.GetTableReference("MyTable");

    var tableQuery = table.CreateQuery<MyTable>()
        .Where(predicate)
        .AsTableQuery(); // << convert back from IQueryable to TableQuery

    var onePage = await table.ExecuteQuerySegmentedAsync(tableQuery, null);
    return onePage.Results;
}

Where MyTable implements ITableEntity and extends custom columns.

Note if the query is likely to return more than one page of data, then you'll need to replace the null with a TableContinuationToken and collect the pages in a loop.

I do agree that the number of, and guidance toward, client libraries for Azure Table storage is becoming quite frustrating.

Answer 2

Since Google and Bing can't seem to understand the difference with WATS vs Azure.Data.Tables I am leaving this example here for others searching for how to use the new SDK v12

    AsyncPageable<SimpleEntity> EventsQueryAsyncTask(CancellationToken ct)
    {
        var rowKeyStart = partition.EventVersionRowKey(startVersion);
        var rowKeyEnd = partition.EventVersionRowKey(startVersion + sliceSize - 1);

        var partitioned = partition.AsPartitionExpression<SimpleEntity>();

        var expression = partitioned.Body;
        var parameters = partitioned.Parameters[0]; // NOTE: use this if you have parameters to pass into your expression otherwise remove this variable...

        var lambda = Expression.Lambda<Func<SimpEntity, bool>>
        (
            Expression.AndAlso
            (
                expression,
                Query.WithinRangeAndLowerBoundEquality<SimpEntity>(rowKeyStart, rowKeyEnd).Body
            ),
            parameters // see comment above...
        );

        return client.QueryAsync
        (
            filter: lambda,
            maxPerPage: 100,
            select: null, // or pass in an IEnumerable<string> of columns you want to limit the projection to...
            cancellationToken: ct
        );
    }