Importing non-events disguised as events from Snowflake causes error.

If the title makes you scratch your head, fear not, I scratched mine so much it hurts.

Also, I am as new as it gets to Amplitude, so I might be missing something really basic.

All our marketing spend, coming from a dozen or so partners is stored in Snowflake, where it is also harmonised to our in-house tracking setup. It is not event-like by nature, but I was asked to try to bring it to Amplitude nonetheless, so I tried to make it appear as event-like as possible.

Below my attempt, as simple as pretending all our costs pertain to one user, mr. string-zero.

CREATE OR REPLACE VIEW a_db.a_schema.a_view_exposed_to_amplitude
AS 
SELECT
	'0' AS user_id,
	to_timestamp_ntz(a_date_field) AS ts,
    date_part(epoch_millisecond, a_date_field::timestamp) AS epoch,
    'costs_per_cid' AS event_type, 
    object_construct('cid', cost_token, 'clicks',clicks, 'usd_costs', costs, 'impressions', impressions) AS event_properties,
    object_construct() AS user_properties
FROM a_db.a_schema.a_cost_table
;

All went well as I created the connection, the SQL in the connection setup is as simple as it gets

SELECT
  user_id AS "user_id",
  event_type AS "event_type",
  event_properties AS "event_properties",
  epoch AS "time", -- must be in milliseconds since epoch (timestamp)
  user_properties AS "user_properties", -- must be JSON
  ts AS "update_time_column"
FROM a_db.a_schema.a_view_exposed_to_amplitude

But once the initial ingestion job kicked in, it brought in 0 events, just a couple million errors :) 

All looking the same

"error":"events must have either user_id or device_id or both (Missing device or user id)

From my perspective the dataset I created has a user_id. Granted, it’s ‘0’ for all of them, but is that the issue or am I missing something more fundamental?