Optimize the query for Unique test

[razze76]

I am running dbt on top of AWS Aurora Postgres and I am running into all sorts of performance issues. One that could be easily fixed is the query for the unique tests.

The current query uses an unnecessary "with" that causes (at least) Postgrest to create a temp table with all data as part of the query. And any indexes existing on the original table can't be utilized.
The with block could be removed and a simpler subquery used instead which would eliminate the need for this temp table and increase performance

Current query:

select count(*) as failures, count(*) != 0 as should_warn, count(*) != 0 as should_error from ( with validation_errors as ( select <unique column>, count(*) as row_count from <table> group by <unique column> having count(*) > 1 or <unique column> is null ) select * from validation_errors ) dbt_internal_test

This can be rewritten to

select count(*) as failures, count(*) != 0 as should_warn, count(*) != 0 as should_error from ( select <unique column>, count(*) as row_count from <table> group by <unique column> having count(*) > 1 or <unique column> is null )
which would eliminate creating the temp table, and enable using any existing indexes on the original table