1 files changed, 44 insertions, 0 deletions
diff --git a/db/migrate/20170320173259_migrate_assignees.rb b/db/migrate/20170320173259_migrate_assignees.rb
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+++ b/db/migrate/20170320173259_migrate_assignees.rb
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+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class MigrateAssignees < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  # When a migration requires downtime you **must** uncomment the following
+  # constant and define a short and easy to understand explanation as to why the
+  # migration requires downtime.
+  # DOWNTIME_REASON = ''
+
+  # When using the methods "add_concurrent_index" or "add_column_with_default"
+  # you must disable the use of transactions as these methods can not run in an
+  # existing transaction. When using "add_concurrent_index" make sure that this
+  # method is the _only_ method called in the migration, any other changes
+  # should go in a separate migration. This ensures that upon failure _only_ the
+  # index creation fails and can be retried or reverted easily.
+  #
+  # To disable transactions uncomment the following line and remove these
+  # comments:
+  disable_ddl_transaction!
+
+  def up
+    # Optimisation: this accounts for most of the invalid assignee IDs on GitLab.com
+    update_column_in_batches(:issues, :assignee_id, nil) do |table, query|
+      query.where(table[:assignee_id].eq(0))
+    end
+
+    users = Arel::Table.new(:users)
+
+    update_column_in_batches(:issues, :assignee_id, nil) do |table, query|
+      query.where(table[:assignee_id].not_eq(nil)\
+        .and(
+          users.project("true").where(users[:id].eq(table[:assignee_id])).exists.not
+        ))
+    end
+  end
+
+  def down
+  end
+end