How to get a count of database rows in Appian web api ?

I am trying to write a custom web-api in Appian that will [among other things] return a count of the number of rows in a database table. To that end, I have added this local variable in my api code.

local!countOfRows: a!queryEntity(
    entity: cons!MY_DATABASE_TABLE_DS,
    query: a!query(
      pagingInfo: a!pagingInfo(
        startIndex: 1,
        batchSize: -1
      )
    ),
    fetchTotalCount: true
  ).totalCount,