Method join

join.go:246–352

(left, right *DataTable)

}

func (j *joinImpl) join(left, right *DataTable) (*DataTable, error) {
	if left == nil {
		err := errors.New("left is nil datatable")
		return nil, errors.Wrap(err, ErrNilDatatable.Error())
	}
	if right == nil {
		err := errors.New("right is nil datatable")
		return nil, errors.Wrap(err, ErrNilDatatable.Error())
	}

	clauses := [2]*joinClause{
		&joinClause{
			table:         left,
			mcols:         j.mcols,
			includeOnCols: true,
		},
		&joinClause{
			table: right,
			mcols: j.mcols,
		},
	}

	// find on clauses
	for _, o := range j.on {
		if o.Table == left.Name() {
			clauses[0].on = append(clauses[0].on, o.Field)
			continue
		}

		if o.Table == right.Name() {
			clauses[1].on = append(clauses[1].on, o.Field)
			continue
		}

		if o.Table == "*" || len(o.Table) == 0 {
			clauses[0].on = append(clauses[0].on, o.Field)
			clauses[1].on = append(clauses[1].on, o.Field)
		}
	}

	// create output
	out := New(left.Name())
	for _, clause := range clauses {
		if err := clause.copyColumnsTo(out); err != nil {
			return nil, err
		}
	}

	// mode
	var ref, join *joinClause
	switch j.mode {
	case innerJoin, leftJoin, outerJoin:
		ref, join = clauses[0], clauses[1]
	case rightJoin:
		ref, join = clauses[1], clauses[0]
	default:
		err := errors.Errorf("unknown mode '%v'", j.mode)
		return nil, errors.Wrap(err, ErrUnknownMode.Error())