merge into moves t
  using(
          select 1 doc_id, d.agent_id, o.mult
                ,1 ccc
                ,1 ddd
          from doc_list d
          join optypes o on d.optype_id=o.id
          where d.id=1
        ) s
  on t.agent_id = s.agent_id and t.doc_id = s.doc_id
  when matched then update set cost_purchase=0;

PLAN JOIN (S D INDEX (PK_DOC_LIST), T INDEX (MOVES_AGENT_DOC_UNQ), S O INDEX (PK_OPTYPES))