Fix migration script not being able to run if it fails midway (#16312)

* Fix migration script not being able to run if it fails midway

* Fix old migration script

* Fix old migration script

* Refactor CorruptionError

3 files changed, 25 insertions, 13 deletions

diff --git a/db/migrate/20190726175042_add_case_insensitive_index_to_tags.rb b/db/migrate/20190726175042_add_case_insensitive_index_to_tags.rb
index eb03d7ca7..3a6527f65 100644
--- a/db/migrate/20190726175042_add_case_insensitive_index_to_tags.rb
+++ b/db/migrate/20190726175042_add_case_insensitive_index_to_tags.rb
@@ -15,7 +15,13 @@ class AddCaseInsensitiveIndexToTags < ActiveRecord::Migration[5.2]
       Tag.where(id: redundant_tag_ids).in_batches.delete_all
     end
 
-    safety_assured { execute 'CREATE UNIQUE INDEX CONCURRENTLY index_tags_on_name_lower ON tags (lower(name))' }
+    begin
+      safety_assured { execute 'CREATE UNIQUE INDEX CONCURRENTLY index_tags_on_name_lower ON tags (lower(name))' }
+    rescue ActiveRecord::StatementInvalid
+      remove_index :tags, name: 'index_tags_on_name_lower'
+      raise
+    end
+
     remove_index :tags, name: 'index_tags_on_name'
     remove_index :tags, name: 'hashtag_search_index'
   end
diff --git a/db/migrate/20200620164023_add_fixed_lowercase_index_to_accounts.rb b/db/migrate/20200620164023_add_fixed_lowercase_index_to_accounts.rb
index c3aa8e33c..366bf9aa7 100644
--- a/db/migrate/20200620164023_add_fixed_lowercase_index_to_accounts.rb
+++ b/db/migrate/20200620164023_add_fixed_lowercase_index_to_accounts.rb
@@ -1,15 +1,9 @@
-class AddFixedLowercaseIndexToAccounts < ActiveRecord::Migration[5.2]
-  disable_ddl_transaction!
+require Rails.root.join('lib', 'mastodon', 'migration_helpers')
 
-  class CorruptionError < StandardError
-    def cause
-      nil
-    end
+class AddFixedLowercaseIndexToAccounts < ActiveRecord::Migration[5.2]
+  include Mastodon::MigrationHelpers
 
-    def backtrace
-      []
-    end
-  end
+  disable_ddl_transaction!
 
   def up
     if index_name_exists?(:accounts, 'old_index_accounts_on_username_and_domain_lower') && index_name_exists?(:accounts, 'index_accounts_on_username_and_domain_lower')
@@ -21,7 +15,8 @@ class AddFixedLowercaseIndexToAccounts < ActiveRecord::Migration[5.2]
     begin
       add_index :accounts, "lower (username), COALESCE(lower(domain), '')", name: 'index_accounts_on_username_and_domain_lower', unique: true, algorithm: :concurrently
     rescue ActiveRecord::RecordNotUnique
-      raise CorruptionError, 'Migration failed because of index corruption, see https://docs.joinmastodon.org/admin/troubleshooting/index-corruption/#fixing'
+      remove_index :accounts, name: 'index_accounts_on_username_and_domain_lower'
+      raise CorruptionError
     end
 
     remove_index :accounts, name: 'old_index_accounts_on_username_and_domain_lower' if index_name_exists?(:accounts, 'old_index_accounts_on_username_and_domain_lower')
diff --git a/db/migrate/20210421121431_add_case_insensitive_btree_index_to_tags.rb b/db/migrate/20210421121431_add_case_insensitive_btree_index_to_tags.rb
index ed359e8cd..e492c9e86 100644
--- a/db/migrate/20210421121431_add_case_insensitive_btree_index_to_tags.rb
+++ b/db/migrate/20210421121431_add_case_insensitive_btree_index_to_tags.rb
@@ -1,8 +1,19 @@
+require Rails.root.join('lib', 'mastodon', 'migration_helpers')
+
 class AddCaseInsensitiveBtreeIndexToTags < ActiveRecord::Migration[5.2]
+  include Mastodon::MigrationHelpers
+
   disable_ddl_transaction!
 
   def up
-    safety_assured { execute 'CREATE UNIQUE INDEX CONCURRENTLY index_tags_on_name_lower_btree ON tags (lower(name) text_pattern_ops)' }
+    begin
+      safety_assured { execute 'CREATE UNIQUE INDEX CONCURRENTLY index_tags_on_name_lower_btree ON tags (lower(name) text_pattern_ops)' }
+    rescue ActiveRecord::StatementInvalid => e
+      remove_index :tags, name: 'index_tags_on_name_lower_btree'
+      raise CorruptionError if e.is_a?(ActiveRecord::RecordNotUnique)
+      raise e
+    end
+
     remove_index :tags, name: 'index_tags_on_name_lower'
   end