Equivalent of select query without passing primary key in DynamoDB?

Question

What will be the equivalent of below query in DynamoDB:

select field1,fields2 from table_name where filter1 == 'filter_value'

Please note that filter1 is not the primary key here, it can be any column in the table.

From what I have read, I understand that it can be achieved using scan() operation but it will return whole data not just fields we specify.
Also, I have read everywhere that we should avoid using scan() as it is heavy operation (scans whole table).

Answer 1

Using the AWS Command Line Interface, you would do it like this

aws dynamodb scan \
     --table-name table_name\
     --projection-expression "field1,fields2" \
     --filter-expression "filter1 = :filter_value"\

A scan always reads every row in the database. A filter expression simply limits what is returned to you. By default you get all attributes ('columns') back for each item but you can limit that using a projection expression.

Queries can be used when you are searching on an indexed attribute.

For information checkout the docs on scans and query