inancgumus/learngo · error

wrong number of fields %q

Error message

wrong number of fields %q

What it means

parseFields enforces the fixed log schema of fieldsLength (4) columns: domain, page, visits, uniques. When strings.Fields yields a different count — extra whitespace-separated tokens or missing columns — it returns this error with the offending fields slice quoted instead of a record. The %q on a []string prints like ["domain" "page" ...].

Source

Thrown at logparser/functional/result.go:38

// parseFields parses and returns the parsing result
func parseFields(line string) (r result, err error) {
	fields := strings.Fields(line)

	if len(fields) != fieldsLength {
		return r, fmt.Errorf("wrong number of fields %q", fields)
	}

	r.domain = fields[0]
	r.page = fields[1]

	f := new(field)
	r.visits = f.uatoi("visits", fields[2])
	r.uniques = f.uatoi("uniques", fields[3])

	return r, f.err
}

View on GitHub (pinned to 3c475a78e5)

Solutions

1. Skip the malformed line and continue parsing the remaining log.
2. Fix the log line so it has exactly four columns: domain page visits uniques.
3. Log the offending line with its number for later correction of the input data.

When it happens

Trigger: Thrown at logparser/functional/result.go:38 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of inancgumus/learngo@3c475a78e5 (2026-09-02). Data as JSON: /api/errors/944fdb682dc996c4. Report an issue: GitHub.