Use binary column

db/migrate/20190220150130_add_extra_shas_to_ci_pipelines.rb

@@ -6,7 +6,7 @@ class AddExtraShasToCiPipelines < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change
-    add_column :ci_pipelines, :source_sha, :string
-    add_column :ci_pipelines, :target_sha, :string
+    add_column :ci_pipelines, :source_sha, :binary
+    add_column :ci_pipelines, :target_sha, :binary
   end
 end

db/schema.rb

@@ -491,8 +491,8 @@
     t.integer "failure_reason"
     t.integer "iid"
     t.integer "merge_request_id"
-    t.string "source_sha"
-    t.string "target_sha"
+    t.binary "source_sha"
+    t.binary "target_sha"
     t.index ["auto_canceled_by_id"], name: "index_ci_pipelines_on_auto_canceled_by_id", using: :btree
     t.index ["merge_request_id"], name: "index_ci_pipelines_on_merge_request_id", where: "(merge_request_id IS NOT NULL)", using: :btree
     t.index ["pipeline_schedule_id"], name: "index_ci_pipelines_on_pipeline_schedule_id", using: :btree