Method ParseSequence

pkg/filter/ql/parser.go:56–203

ParseSequence parses the collection of binary expressions with possible join statements and time frame constraints. This method assumes the SEQUENCE token has already been consumed.

()

// statements and time frame constraints. This method assumes the SEQUENCE token
// has already been consumed.
func (p *Parser) ParseSequence() (*Sequence, error) {
	seq := &Sequence{}
	var exprs []SequenceExpr

	// parse optional max span
	tok, _, _ := p.scanIgnoreWhitespace()
	if tok == MaxSpan {
		var err error
		seq.MaxSpan, err = p.parseDuration()
		if err != nil {
			return nil, err
		}
		if seq.MaxSpan > time.Hour*4 {
			return nil, fmt.Errorf("maximum span %v cannot be greater than 4h", seq.MaxSpan)
		}
	} else {
		p.unscan()
	}

	// parse optional global link
	tok, _, _ = p.scanIgnoreWhitespace()
	if tok == By {
		tok, pos, lit := p.scanIgnoreWhitespace()
		if !fields.IsField(lit) {
			return nil, newParseError(tokstr(tok, lit), []string{"field"}, pos, p.expr)
		}
		var err error
		field, err := p.parseField(lit)
		if err != nil {
			return nil, err
		}

		seqLink := &SequenceLink{Fields: []*FieldLiteral{field}}

		// handle multiple join fields separated by comma
		for {
			if tok, _, _ := p.scanIgnoreWhitespace(); tok != Comma {
				p.unscan()
				break
			}

			tok, pos, lit := p.scanIgnoreWhitespace()
			if !fields.IsField(lit) {
				return nil, newParseError(tokstr(tok, lit), []string{"field"}, pos, p.expr)
			}
			field, err := p.parseField(lit)
			if err != nil {
				return nil, err
			}

			seqLink.Fields = append(seqLink.Fields, field)
		}

		seq.By = seqLink
	} else {
		p.unscan()
	}