Big Query Materialized view : bytes_billed is different when used in a sub query

Google Cloud Data Analytics
1

Hi

I’ve got a Materialized view partition by date.
When I query one day on the materialized view only I get :

  • Bytes processed : 516.54 MB
  • Bytes billed : 20 MB

When I use the same SQL in a Sub query I get :

  • Bytes processed : 518.86 MB
  • Bytes billed : 519 MB

Some details
- Querying baseTable1 only : Bytes processed 2.32 MB, billed 10MB

  • In both case I can see in the Execution details that the materialized view is being used fully (not pulling data from a base tables)
  • Materialized view has a LEFT JOIN between baseTable1 and another one
  • The Input step using the materialized view has the same Records read in both case
  • Same issue when using LEFT JOIN instead of WHERE IN
SELECT field1, field2
FROM baseTable1
WHERE LocalDate = '2024-06-13' -- Partition 
AND field2 IN (
  -- Materialized view SQL starts
  SELECT field2
  FROM materializedView
  WHERE LocalDate = '2024-06-13' -- Partition
  -- Materialized view SQL end
 )