Add post migration to migrate Security Scans

This is the final step in migrating Security
Job Artifacts to Security::Scan.

The temporary index has been removed.

changelogs/unreleased/cleanup-migration-to-security-scans.yml

+---
+title: Complete the migration of Job Artifact to Security Scan
+merge_request: 24244
+author:
+type: other

db/post_migrate/20200323011225_complete_migrate_security_scans.rb

+# frozen_string_literal: true
+
+class CompleteMigrateSecurityScans < ActiveRecord::Migration[6.0]
+  disable_ddl_transaction!
+
+  def up
+    Gitlab::BackgroundMigration.steal('MigrateSecurityScans')
+  end
+
+  def down
+    # intentionally blank
+  end
+end

db/post_migrate/20200323011955_remove_index_used_for_scan_migration.rb

+# frozen_string_literal: true
+
+class RemoveIndexUsedForScanMigration < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  INDEX_NAME = 'job_artifacts_secure_reports_temp_index'
+  COLUMNS = [:id, :file_type, :job_id, :created_at, :updated_at]
+
+  disable_ddl_transaction!
+
+  def up
+    if index_exists?(:ci_job_artifacts, COLUMNS, name: INDEX_NAME)
+      remove_concurrent_index(:ci_job_artifacts, COLUMNS, name: INDEX_NAME)
+    end
+  end
+
+  def down
+    add_concurrent_index(:ci_job_artifacts,
+                         COLUMNS,
+                         name: INDEX_NAME,
+                         where: 'file_type BETWEEN 5 AND 8')
+  end
+end

db/structure.sql

@@ -10214,8 +10214,6 @@ CREATE UNIQUE INDEX issue_user_mentions_on_issue_id_and_note_id_index ON public.
 
 CREATE UNIQUE INDEX issue_user_mentions_on_issue_id_index ON public.issue_user_mentions USING btree (issue_id) WHERE (note_id IS NULL);
 
-CREATE INDEX job_artifacts_secure_reports_temp_index ON public.ci_job_artifacts USING btree (id, file_type, job_id, created_at, updated_at) WHERE ((file_type >= 5) AND (file_type <= 8));
-
 CREATE UNIQUE INDEX kubernetes_namespaces_cluster_and_namespace ON public.clusters_kubernetes_namespaces USING btree (cluster_id, namespace);
 
 CREATE INDEX merge_request_mentions_temp_index ON public.merge_requests USING btree (id) WHERE ((description ~~ '%@%'::text) OR ((title)::text ~~ '%@%'::text));
@@ -12800,6 +12798,8 @@ COPY "schema_migrations" (version) FROM STDIN;
 20200319203901
 20200320112455
 20200320123839
+20200323011225
+20200323011955
 20200323071918
 20200323074147
 20200323075043