Is this the right approach to using DynamoDB where the only Query field is of KeyType Boolean?

I have data that requires two types of access:

1. a unique identifier to retrieve a single row
2. the retrieval of a batch of rows by a field equalling False

The main table can contain many fields (e.g., 100).

In DynamoDB I have a schema defining a primary key and a Global Secondary Index defining a field of KeyType Number which I set to 0 or 1.

The table itself contains many fields so this set-up is expensive. i.e. many fields are copied to the Global Secondary Index when the main table changes.

Can it be better to store the primary key of the main table in the Global Secondary Index and then perform individual looks-up from the rows retued by a Global Secondary Index Query?