Function parseGroupby

dql/parser.go:2359–2431

parseGroupby parses the groupby directive.

(it *lex.ItemIterator, gq *GraphQuery)

// parseGroupby parses the groupby directive.
func parseGroupby(it *lex.ItemIterator, gq *GraphQuery) error {
	count := 0
	expectArg := true
	it.Next()
	item := it.Item()
	alias := ""
	if item.Typ != itemLeftRound {
		return item.Errorf("Expected a left round after groupby")
	}

loop:
	for it.Next() {
		item := it.Item()
		switch item.Typ {
		case itemRightRound:
			break loop
		case itemComma:
			if expectArg {
				return item.Errorf("Expected a predicate but got comma")
			}
			expectArg = true
		case itemName:
			if !expectArg {
				return item.Errorf("Expected a comma or right round but got: %v", item.Val)
			}

			val := collectName(it, item.Val)
			peekIt, err := it.Peek(1)
			if err != nil {
				return err
			}
			if peekIt[0].Typ == itemColon {
				if alias != "" {
					return item.Errorf("Expected predicate after %s:", alias)
				}
				if validKey(val) {
					return item.Errorf("Can't use keyword %s as alias in groupby", val)
				}
				alias = val
				it.Next() // Consume the itemColon
				continue
			}

			var langs []string
			items, err := it.Peek(1)
			if err == nil && items[0].Typ == itemAt {
				it.Next() // consume '@'
				it.Next() // move forward
				langs, err = parseLanguageList(it)
				if err != nil {
					return err
				}
			}
			attrLang := GroupByAttr{
				Attr:  val,
				Alias: alias,
				Langs: langs,
			}