postgres sql merge upsert

https://www.jb51.net/article/156093.htm

• 插入，关于冲突-无所事事.
  insert into dummy(id, name, size) values(1, 'new_name', 3) on conflict do nothing;

• 插入，关于冲突-做更新，指定冲突目标列.
  insert into dummy(id, name, size) values(1, 'new_name', 3) on conflict(id) do update set name = 'new_name', size = 3;

• 插入，关于冲突-做更新，指定冲突目标约束名称.
  insert into dummy(id, name, size) values(1, 'new_name', 3) on conflict on constraint dummy_pkey do update set name = 'new_name', size = 4;