[EE] Remove import columns from projects table
In https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21497, we
migrated all project import data into a separate table,
project_import_data
. In addition, we also added:
ignore_column :import_status, :import_jid, :import_error
In gitlab-com/gl-infra/production#908 (closed), we
observed some of these import_error
columns consumed megabytes of
error backtraces and caused slow loading of projects whenever a
SELECT * from projects
query loaded the row into memory.
Since we have long migrated away from these columns, we can now drop these columns entirely.
CE port: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/29863
Edited by Stan Hu