Set all LockVersion columns to default to 0

We have some custom middleware that makes lock_version behave properly
when it's set to `nil`, but we want to get rid of it, so before that
let's make sure all new data coming in gets defaulted to a good value
instead of `nil`.

db/migrate/20200203025400_default_lock_version_to_zero_for_merge_requests.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class DefaultLockVersionToZeroForMergeRequests < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def change
+    with_lock_retries do
+      change_column_default :merge_requests, :lock_version, from: nil, to: 0
+    end
+  end
+end

db/migrate/20200203025602_default_lock_version_to_zero_for_issues.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class DefaultLockVersionToZeroForIssues < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def change
+    with_lock_retries do
+      change_column_default :issues, :lock_version, from: nil, to: 0
+    end
+  end
+end

db/migrate/20200203025619_default_lock_version_to_zero_for_epics.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class DefaultLockVersionToZeroForEpics < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def change
+    with_lock_retries do
+      change_column_default :epics, :lock_version, from: nil, to: 0
+    end
+  end
+end

db/migrate/20200203025744_default_lock_version_to_zero_for_ci_builds.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class DefaultLockVersionToZeroForCiBuilds < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def change
+    with_lock_retries do
+      change_column_default :ci_builds, :lock_version, from: nil, to: 0
+    end
+  end
+end

db/migrate/20200203025801_default_lock_version_to_zero_for_ci_stages.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class DefaultLockVersionToZeroForCiStages < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def change
+    with_lock_retries do
+      change_column_default :ci_stages, :lock_version, from: nil, to: 0
+    end
+  end
+end

db/migrate/20200203025821_default_lock_version_to_zero_for_ci_pipelines.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class DefaultLockVersionToZeroForCiPipelines < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def change
+    with_lock_retries do
+      change_column_default :ci_pipelines, :lock_version, from: nil, to: 0
+    end
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_01_30_161817) do
+ActiveRecord::Schema.define(version: 2020_02_03_025821) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
@@ -659,7 +659,7 @@ ActiveRecord::Schema.define(version: 2020_01_30_161817) do
     t.text "yaml_variables"
     t.datetime "queued_at"
     t.string "token"
-    t.integer "lock_version"
+    t.integer "lock_version", default: 0
     t.string "coverage_regex"
     t.integer "auto_canceled_by_id"
     t.boolean "retried"
@@ -835,7 +835,7 @@ ActiveRecord::Schema.define(version: 2020_01_30_161817) do
     t.datetime "finished_at"
     t.integer "duration"
     t.integer "user_id"
-    t.integer "lock_version"
+    t.integer "lock_version", default: 0
     t.integer "auto_canceled_by_id"
     t.integer "pipeline_schedule_id"
     t.integer "source"
@@ -949,7 +949,7 @@ ActiveRecord::Schema.define(version: 2020_01_30_161817) do
     t.datetime "updated_at"
     t.string "name"
     t.integer "status"
-    t.integer "lock_version"
+    t.integer "lock_version", default: 0
     t.integer "position"
     t.index ["pipeline_id", "name"], name: "index_ci_stages_on_pipeline_id_and_name", unique: true
     t.index ["pipeline_id", "position"], name: "index_ci_stages_on_pipeline_id_and_position"
@@ -1523,7 +1523,7 @@ ActiveRecord::Schema.define(version: 2020_01_30_161817) do
     t.integer "cached_markdown_version"
     t.integer "updated_by_id"
     t.integer "last_edited_by_id"
-    t.integer "lock_version"
+    t.integer "lock_version", default: 0
     t.date "start_date"
     t.date "end_date"
     t.datetime "last_edited_at"
@@ -2140,7 +2140,7 @@ ActiveRecord::Schema.define(version: 2020_01_30_161817) do
     t.boolean "confidential", default: false, null: false
     t.date "due_date"
     t.integer "moved_to_id"
-    t.integer "lock_version"
+    t.integer "lock_version", default: 0
     t.text "title_html"
     t.text "description_html"
     t.integer "time_estimate"
@@ -2562,7 +2562,7 @@ ActiveRecord::Schema.define(version: 2020_01_30_161817) do
     t.integer "approvals_before_merge"
     t.string "rebase_commit_sha"
     t.string "in_progress_merge_commit_sha"
-    t.integer "lock_version"
+    t.integer "lock_version", default: 0
     t.text "title_html"
     t.text "description_html"
     t.integer "time_estimate"