How to use wild card character * in dynamodb query operation?

Question

I am using aws-ruby-sdk for accessing dynamodb. I want to use query operation and get all items. So I am using wildcard character * in expression_attribute_values. It doesn't work. However, if I specify a specific value, it works.

How do I use * ? Below is my code to query dynamodb:

db_client.query({
        table_name: "my_table_name",
        key_condition_expression: "#idtype = :idType",
        expression_attribute_names: {
             "#idtype" => "IdType"
         },
        expression_attribute_values: {
             ":idType" => "*",
        },
    })

Also I am specifying * because I want all values. End result I want is only unique values in the primary key IdType but there seem to be no way to have unique constraint in dynamodb (not that I know of) so I am fetching all values and will have unique values from the result using my own code.

Any help would be appreciated.

PS: Primary Partition Key - IdType is a String

Solution

You can use the Scan API to get all items in a DynamoDB table. If you only need the primary keys, you can use a ProjectionExpression="IdType" to limit the amount of data you send back.

db_client.scan({table_name: "my_table_name"})