Finalize conversion to bigint for ci_build_needs

1. Ensure the migration of `build_id` to `bigint` is completed
2. Copy indexe and FK
3. Swap columns

See https://gitlab.com/gitlab-org/gitlab/-/issues/328046.

Changelog: other

db/post_migrate/20210701033622_finalize_ci_builds_needs_bigint_conversion.rb

+# frozen_string_literal: true
+
+class FinalizeCiBuildsNeedsBigintConversion < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  TABLE_NAME = 'ci_build_needs'
+
+  def up
+    ensure_batched_background_migration_is_finished(
+      job_class_name: 'CopyColumnUsingBackgroundMigrationJob',
+      table_name: TABLE_NAME,
+      column_name: 'id',
+      job_arguments: [['build_id'], ['build_id_convert_to_bigint']]
+    )
+
+    swap
+  end
+
+  def down
+    swap
+  end
+
+  private
+
+  def swap
+    # This is to replace the existing "index_ci_build_needs_on_build_id_and_name" UNIQUE, btree (build_id, name)
+    add_concurrent_index TABLE_NAME, [:build_id_convert_to_bigint, :name], unique: true, name: 'index_ci_build_needs_on_build_id_convert_to_bigint_and_name'
+
+    # Add a foreign key on `build_id_convert_to_bigint` before we swap the columns and drop the old FK (fk_rails_3cf221d4ed)
+    add_concurrent_foreign_key TABLE_NAME, :ci_builds,
+      column: :build_id_convert_to_bigint, on_delete: :cascade,
+      name: 'fk_rails_3cf221d4ed_tmp', reverse_lock_order: true
+
+    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 ci_builds, #{TABLE_NAME} IN ACCESS EXCLUSIVE MODE"
+
+      # Swap column names
+      temp_name = 'build_id_tmp'
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:build_id)} TO #{quote_column_name(temp_name)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:build_id_convert_to_bigint)} TO #{quote_column_name(:build_id)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(temp_name)} TO #{quote_column_name(:build_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(:build_id, :build_id_convert_to_bigint)
+      execute "ALTER FUNCTION #{quote_table_name(function_name)} RESET ALL"
+
+      # Swap defaults
+      change_column_default TABLE_NAME, :build_id, nil
+      change_column_default TABLE_NAME, :build_id_convert_to_bigint, 0
+
+      # 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_ci_build_needs_on_build_id_and_name'
+      rename_index TABLE_NAME, 'index_ci_build_needs_on_build_id_convert_to_bigint_and_name', 'index_ci_build_needs_on_build_id_and_name'
+
+      # Drop original FK on the old int4 `build_id` (fk_rails_3cf221d4ed)
+      remove_foreign_key TABLE_NAME, name: 'fk_rails_3cf221d4ed'
+      # We swapped the columns but the FK for buil_id is still using the temporary name for the buil_id_convert_to_bigint column
+      # So we have to also swap the FK name now that we dropped the other one with the same
+      rename_constraint(TABLE_NAME, 'fk_rails_3cf221d4ed_tmp', 'fk_rails_3cf221d4ed')
+    end
+  end
+end

db/schema_migrations/20210701033622

+e38d73441ddd7f6238a66ee86009c445ad6056f3e6872e7a6c72abe051294d7e
\ No newline at end of file

db/structure.sql

@@ -10487,11 +10487,11 @@ ALTER SEQUENCE chat_teams_id_seq OWNED BY chat_teams.id;
 
 CREATE TABLE ci_build_needs (
     id integer NOT NULL,
-    build_id integer NOT NULL,
+    build_id_convert_to_bigint integer DEFAULT 0 NOT NULL,
     name text NOT NULL,
     artifacts boolean DEFAULT true NOT NULL,
     optional boolean DEFAULT false NOT NULL,
-    build_id_convert_to_bigint bigint DEFAULT 0 NOT NULL
+    build_id bigint NOT NULL
 );
 
 CREATE SEQUENCE ci_build_needs_id_seq