Aggregate function that picks any/first/last/random value

I run a query which looks like below

WITH src AS (
    ...
)
SELECT MAX(field1), array_agg(field2)
FROM src

I have knowledge that field1 is the same across all rows returned from src so I really don't really care whether the aggregate function used with it is MAX or MIN. In my case field1 is an array so I am curious if there is a more efficient way to grab any value of field1 which doesn't include overhead of comparing it with the previously saved MIN/MAX. If there was a function to grab the first / retain the last value of field1 that would be ideal.

I believe I found a more efficient SQL for what I am trying to achieve

WITH src AS (
    ...
)
, identical_field1 (
    SELECT field1 FROM src LIMIT 1
)
SELECT (SELECT field1 FROM identical_field1), array_agg(field2)
FROM src

Sub-select on field1 is evaluated only once and only requests one single row from src.

I am not marking it as an answer for now 'cause someone may still suggest a more efficient way.

StackExchange Database Administrators Q#188230, answer score: 5