1 files changed, 88 insertions, 0 deletions
diff --git a/db/post_migrate/20210806131706_finalize_taggins_bigint_conversion.rb b/db/post_migrate/20210806131706_finalize_taggins_bigint_conversion.rb
new file mode 100644
index 00000000000..beb15e77878
--- /dev/null
+++ b/db/post_migrate/20210806131706_finalize_taggins_bigint_conversion.rb
@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+class FinalizeTagginsBigintConversion < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  TABLE_NAME = 'taggings'
+
+  def up
+    ensure_batched_background_migration_is_finished(
+      job_class_name: 'CopyColumnUsingBackgroundMigrationJob',
+      table_name: TABLE_NAME,
+      column_name: 'id',
+      job_arguments: [%w[id taggable_id], %w[id_convert_to_bigint taggable_id_convert_to_bigint]]
+    )
+
+    swap
+  end
+
+  def down
+    swap
+  end
+
+  private
+
+  def swap
+    # rubocop:disable Migration/PreventIndexCreation
+    add_concurrent_index TABLE_NAME, :id_convert_to_bigint, unique: true, name: 'index_taggings_on_id_convert_to_bigint'
+
+    # This is to replace the existing "index_taggings_on_taggable_id_and_taggable_type" btree (taggable_id, taggable_type)
+    add_concurrent_index TABLE_NAME, [:taggable_id_convert_to_bigint, :taggable_type], name: 'i_taggings_on_taggable_id_convert_to_bigint_and_taggable_type'
+
+    # This is to replace the existing "index_taggings_on_taggable_id_and_taggable_type_and_context" btree (taggable_id, taggable_type, context)
+    add_concurrent_index TABLE_NAME, [:taggable_id_convert_to_bigint, :taggable_type, :context], name: 'i_taggings_on_taggable_bigint_and_taggable_type_and_context'
+
+    # This is to replace the existing "taggings_idx" btree (tag_id, taggable_id, taggable_type, context, tagger_id, tagger_type)
+    add_concurrent_index TABLE_NAME, [:tag_id, :taggable_id_convert_to_bigint, :taggable_type, :context, :tagger_id, :tagger_type], unique: true, name: 'taggings_idx_tmp'
+
+    # This is to replace the existing "tmp_index_taggings_on_id_where_taggable_type_project" btree (id) WHERE taggable_type::text = 'Project'::text
+    add_concurrent_index TABLE_NAME, :id_convert_to_bigint, where: "taggable_type = 'Project'", name: 'tmp_index_taggings_on_id_bigint_where_taggable_type_project'
+    # rubocop:enable Migration/PreventIndexCreation
+
+    with_lock_retries(raise_on_exhaustion: true) do
+      # We'll need  ACCESS EXCLUSIVE lock on the related tables,
+      # lets make sure it can be acquired from the start
+      execute "LOCK TABLE #{TABLE_NAME} IN ACCESS EXCLUSIVE MODE"
+
+      # Swap column names
+      temp_name = 'taggable_id_tmp'
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:taggable_id)} TO #{quote_column_name(temp_name)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:taggable_id_convert_to_bigint)} TO #{quote_column_name(:taggable_id)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(temp_name)} TO #{quote_column_name(:taggable_id_convert_to_bigint)}"
+
+      temp_name = 'id_tmp'
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:id)} TO #{quote_column_name(temp_name)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:id_convert_to_bigint)} TO #{quote_column_name(:id)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(temp_name)} TO #{quote_column_name(:id_convert_to_bigint)}"
+
+      # We need to update the trigger function in order to make PostgreSQL to
+      # regenerate the execution plan for it. This is to avoid type mismatch errors like
+      # "type of parameter 15 (bigint) does not match that when preparing the plan (integer)"
+      function_name = Gitlab::Database::UnidirectionalCopyTrigger.on_table(TABLE_NAME).name([:id, :taggable_id], [:id_convert_to_bigint, :taggable_id_convert_to_bigint])
+      execute "ALTER FUNCTION #{quote_table_name(function_name)} RESET ALL"
+
+      # Swap defaults
+      execute "ALTER SEQUENCE taggings_id_seq OWNED BY #{TABLE_NAME}.id"
+      change_column_default TABLE_NAME, :id, -> { "nextval('taggings_id_seq'::regclass)" }
+      change_column_default TABLE_NAME, :id_convert_to_bigint, 0
+
+      # Swap PK constraint
+      execute "ALTER TABLE #{TABLE_NAME} DROP CONSTRAINT taggings_pkey CASCADE"
+      rename_index TABLE_NAME, 'index_taggings_on_id_convert_to_bigint', 'taggings_pkey'
+      execute "ALTER TABLE #{TABLE_NAME} ADD CONSTRAINT taggings_pkey PRIMARY KEY USING INDEX taggings_pkey"
+
+      # Rename the index on the `bigint` column to match the new column name
+      # (we already hold an exclusive lock, so no need to use DROP INDEX CONCURRENTLY here)
+      execute 'DROP INDEX index_taggings_on_taggable_id_and_taggable_type'
+      rename_index TABLE_NAME, 'i_taggings_on_taggable_id_convert_to_bigint_and_taggable_type', 'index_taggings_on_taggable_id_and_taggable_type'
+      execute 'DROP INDEX index_taggings_on_taggable_id_and_taggable_type_and_context'
+      rename_index TABLE_NAME, 'i_taggings_on_taggable_bigint_and_taggable_type_and_context', 'index_taggings_on_taggable_id_and_taggable_type_and_context'
+      execute 'DROP INDEX taggings_idx'
+      rename_index TABLE_NAME, 'taggings_idx_tmp', 'taggings_idx'
+      execute 'DROP INDEX tmp_index_taggings_on_id_where_taggable_type_project'
+      rename_index TABLE_NAME, 'tmp_index_taggings_on_id_bigint_where_taggable_type_project', 'tmp_index_taggings_on_id_where_taggable_type_project'
+    end
+  end
+end