presto-main/src/main/java/io/prestosql/execution/StageId.java/StageId/equals
class StageId:    @Override
    public boolean equals(Object obj)
    {
        if (this == obj) {
            return true;
        }
        if (obj == null || getClass() != obj.getClass()) {
            return false;
        }
        final StageId other = (StageId) obj;
        return Objects.equals(this.id, other.id) &&
                Objects.equals(this.queryId, other.queryId);
    }