Finalize conversion to bigint for push_event_payloads

This is same change as
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64577, which had
to be reverted and rescheduled for 14.2.

1. Ensure the migration of `event_id` to `event_id_convert_to_bigint` is
completed.
2. Copy indexes and FKs
3. Swap columns

See https://gitlab.com/gitlab-org/gitlab/-/issues/288005.

Changelog: other

db/post_migrate/20210709024048_finalize_push_event_payloads_bigint_conversion_2.rb

+# frozen_string_literal: true
+
+class FinalizePushEventPayloadsBigintConversion2 < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  TABLE_NAME = 'push_event_payloads'
+  INDEX_NAME = 'index_push_event_payloads_on_event_id_convert_to_bigint'
+
+  def up
+    ensure_batched_background_migration_is_finished(
+      job_class_name: 'CopyColumnUsingBackgroundMigrationJob',
+      table_name: TABLE_NAME,
+      column_name: 'event_id',
+      job_arguments: [["event_id"], ["event_id_convert_to_bigint"]]
+    )
+
+    swap_columns
+  end
+
+  def down
+    swap_columns
+  end
+
+  private
+
+  def swap_columns
+    add_concurrent_index TABLE_NAME, :event_id_convert_to_bigint, unique: true, name: INDEX_NAME
+
+    # Add a foreign key on `event_id_convert_to_bigint` before we swap the columns and drop the old FK (fk_36c74129da)
+    add_concurrent_foreign_key TABLE_NAME, :events, column: :event_id_convert_to_bigint, on_delete: :cascade
+
+    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}, events IN ACCESS EXCLUSIVE MODE"
+
+      # Swap column names
+      temp_name = 'event_id_tmp'
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:event_id)} TO #{quote_column_name(temp_name)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(:event_id_convert_to_bigint)} TO #{quote_column_name(:event_id)}"
+      execute "ALTER TABLE #{quote_table_name(TABLE_NAME)} RENAME COLUMN #{quote_column_name(temp_name)} TO #{quote_column_name(:event_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(:event_id, :event_id_convert_to_bigint)
+      execute "ALTER FUNCTION #{quote_table_name(function_name)} RESET ALL"
+
+      # Swap defaults
+      change_column_default TABLE_NAME, :event_id, nil
+      change_column_default TABLE_NAME, :event_id_convert_to_bigint, 0
+
+      # Swap PK constraint
+      execute "ALTER TABLE #{TABLE_NAME} DROP CONSTRAINT push_event_payloads_pkey"
+      rename_index TABLE_NAME, INDEX_NAME, 'push_event_payloads_pkey'
+      execute "ALTER TABLE #{TABLE_NAME} ADD CONSTRAINT push_event_payloads_pkey PRIMARY KEY USING INDEX push_event_payloads_pkey"
+
+      # Drop original FK on the old int4 `event_id` (fk_36c74129da)
+      remove_foreign_key TABLE_NAME, name: concurrent_foreign_key_name(TABLE_NAME, :event_id)
+      # We swapped the columns but the FK for event_id is still using the old name for the event_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,
+        concurrent_foreign_key_name(TABLE_NAME, :event_id_convert_to_bigint),
+        concurrent_foreign_key_name(TABLE_NAME, :event_id)
+      )
+    end
+  end
+end

db/schema_migrations/20210709024048

+d35079b6d6ed38ce8f212a09e684988f7499d456d28f70b6178914b1b17eee5b
\ No newline at end of file

db/structure.sql

@@ -17489,7 +17489,7 @@ ALTER SEQUENCE protected_tags_id_seq OWNED BY protected_tags.id;
 
 CREATE TABLE push_event_payloads (
     commit_count bigint NOT NULL,
-    event_id integer NOT NULL,
+    event_id_convert_to_bigint integer DEFAULT 0 NOT NULL,
     action smallint NOT NULL,
     ref_type smallint NOT NULL,
     commit_from bytea,
@@ -17497,7 +17497,7 @@ CREATE TABLE push_event_payloads (
     ref text,
     commit_title character varying(70),
     ref_count integer,
-    event_id_convert_to_bigint bigint DEFAULT 0 NOT NULL
+    event_id bigint NOT NULL
 );
 
 CREATE TABLE push_rules (