AWS DynamoDB how to retrieve data from multiple tables using CreateMultiTableBatchGet without Range Key

Question

I'm trying to retrieve data from dynamoDB multiple tables, in each table I have hash key and range key however I just have hash key so without range key it doesn't work, it complains like range key missing.

var batchGets = new List<Amazon.DynamoDBv2.DataModel.BatchGet>();

public void SetBatchGet<T>(T entity)
        {
            var batch = context.CreateBatchGet<T>(null);
            batch.AddKey(entity);         /// ERROR : Range key missing 
            batchGets.Add(batch);
        }

public async Task<List<object>> CreateMultiTableBatchGet(DynamoDBOperationConfig dynamoDBOperationConfig = null)
        {
            try
            {
                
                var result = context.CreateMultiTableBatchGet(batchGets.ToArray());
                await result.ExecuteAsync();
                batchGets = new List<Amazon.DynamoDBv2.DataModel.BatchGet>();

                return null;
            }
            catch (System.Exception ex)
            {
                batchGets = new List<Amazon.DynamoDBv2.DataModel.BatchGet>();
                throw ex;
            }
        }


// Caller

 var pr = new Participant();
            pr.Code = Code;  // Just passing hash key.
_repo.SetBatchGet(pr);
_repo.CreateMultiTableBatchGet();

How to make Multitable work without range key.

Answer 1

For a BatchGetItems you have to provide the full primary key, hash and range key. If the range key is unknown you will need to use a Query request where you only need to provide a hash key. However, there is no such thing as a BatchQueryItems.

The closest thing being the PartiQL API ExecuteStatement where you can spoof a "BatchQuery" using the IN operator:

SELECT * FROM mytable WHERE pk IN [1,2,3]