The DDL operation performed, possibly dependent on the pre-existence of the DDL target.
Possible values (new values might be added in the future): "CREATE": The query created the DDL
target. "SKIP": No-op. Example cases: the query is CREATE TABLE IF NOT EXISTS while the table
already exists, or the query is DROP TABLE IF EXISTS while the table does not exist. "REPLACE":
The query replaced the DDL target. Example case: the query is CREATE OR REPLACE TABLE, and the
table already exists. "DROP": The query deleted the DDL target.