vitessio/vitess · error · RowMismatchError

expected %d rows in result, got %d

Error message

expected %d rows in result, got %d

What it means

RowsEquals compares two row sets unordered. Before matching individual rows it checks the cardinality; if want and got have different lengths it returns a RowMismatchError carrying this message plus both full row sets for diffing.

Source

Thrown at go/sqltypes/parse_rows.go:140

type RowMismatchError struct {
	err       error
	want, got []Row
}

func (e *RowMismatchError) Error() string {
	return fmt.Sprintf("results differ: %v\n\twant: %v\n\tgot:  %v", e.err, e.want, e.got)
}

func RowEqual(want, got Row) bool {
	return slices.EqualFunc(want, got, func(a, b Value) bool {
		return a.Equal(b)
	})
}

func RowsEquals(want, got []Row) error {
	if len(want) != len(got) {
		return &RowMismatchError{
			err:  fmt.Errorf("expected %d rows in result, got %d", len(want), len(got)),
			want: want,
			got:  got,
		}
	}

	matched := make([]bool, len(want))
	for _, aa := range want {
		var ok bool
		for i, bb := range got {
			if matched[i] {
				continue
			}
			if RowEqual(aa, bb) {
				matched[i] = true
				ok = true
				break
			}
		}

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Inspect got vs want (RowMismatchError embeds both) to see which side is wrong
2. Fix the query or fixture data so cardinality matches
3. Add/adjust a LIMIT or WHERE clause if the test intent is a subset check

Example fix

// before
query := "select id from t"
// after (if only first row intended)
query := "select id from t limit 1"

if len(got) != expectedCount {
  return fmt.Errorf("pre-check: got %d rows, want %d", len(got), expectedCount)
}

func sameCardinality(want, got []sqltypes.Row) bool { return len(want) == len(got) }

err := sqltypes.RowsEquals(want, got)
var rm *sqltypes.RowMismatchError
if errors.As(err, &rm) {
  t.Logf("want=%v got=%v", rm.Want, rm.Got)
}

When it happens

Trigger: Calling RowsEquals (directly or via RowsEqualsStr / AssertMatchesNoOrder) when the actual query result returned a different number of rows than the expected set.

Common situations: Underlying query changed semantics (added/removed a WHERE clause, missing LIMIT), data set differences between environments, or a streaming test collecting fewer/more rows than expected.

Related errors

• row %v is missing from result
• malformed row assertion: %w
• cannot create local vtctldclient without a server; call SetS
• failed to parse literal string at %s: %w
• unexpected token '%s' at %s

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/13e8f64104a0c3bc. Report an issue: GitHub.