dgraph-io/dgraph · error

while writing schema file

Error message

while writing schema file

What it means

In generateSchemaAndData, the error returned by dumpSchema is re-wrapped with "while writing schema file", adding call-site context (which output file phase failed) on top of dumpSchema's own "while writing schema" wrapper. The root cause remains the underlying write error.

Source

Thrown at dgraph/cmd/migrate/run.go:169

// then it dumps schema to the writer backed by schemaOutput, and data in RDF format
// to the writer backed by dataOutput
func generateSchemaAndData(dumpMeta *dumpMeta, schemaOutput string, dataOutput string) error {
	schemaWriter, schemaCancelFunc, err := getFileWriter(schemaOutput)
	if err != nil {
		return err
	}
	defer schemaCancelFunc()
	dataWriter, dataCancelFunc, err := getFileWriter(dataOutput)
	if err != nil {
		return err
	}
	defer dataCancelFunc()

	dumpMeta.dataWriter = dataWriter
	dumpMeta.schemaWriter = schemaWriter

	if err := dumpMeta.dumpSchema(); err != nil {
		return errors.Wrapf(err, "while writing schema file")
	}
	if err := dumpMeta.dumpTables(); err != nil {
		return errors.Wrapf(err, "while writing data file")
	}
	return nil
}

View on GitHub (pinned to 759e242be6)

Solutions

1. Print the error with %+v to see the full wrap chain and root cause.
2. Check disk space and write permissions for the schema output path.
3. Confirm the schema path is a writable regular file, then rerun migrate.

Example fix

// before
dgraph migrate --schema /etc/dgraph/schema.txt  # read-only dir
// after
mkdir -p ~/migrate-out && dgraph migrate --schema ~/migrate-out/schema.txt

if err := canWrite(filepath.Dir(schemaPath)); err != nil {
	return fmt.Errorf("cannot write schema to %s: %w", schemaPath, err)
}

func isSchemaWriteErr(err error) bool {
	return strings.Contains(err.Error(), "while writing schema file")
}

if err := migrate.Run(); err != nil {
	if isSchemaWriteErr(err) {
		log.Printf("root cause: %+v", errors.Cause(err))
	}
}

When it happens

Trigger: Any failure inside dumpSchema (schemaWriter.WriteString or Flush error) surfaces with this message: unwritable schema output path, disk full, or file handle issues during dgraph migrate.

Common situations: Schema output path is a directory or read-only file; disk quota exceeded; running as a user without write permission on the output directory.

Related errors

• while writing schema
• while writing data file
• while dumping table %s
• not allowed to overwrite %s
• nil value found

AI-assisted analysis of dgraph-io/dgraph@759e242be6 (2026-09-01). Data as JSON: /api/errors/958121d68b16a1d6. Report an issue: GitHub.