Method getRefLabelFromConstraint

dgraph/cmd/migrate/dump.go:267–293

getRefLabelFromConstraint returns a ref label based on a foreign key constraint. Consider the foreign key constraint foreign key (person_company, person_employee_id) references person (company, employee_id) and a row with the following values in the table Google, 100, 50.0 (salary) where Google is t

(foreignTableInfo *sqlTable,
	constraint *fkConstraint)

// the refLabel will use the foreign table name, foreign column names and the local row's values,
// yielding the value of _:person_company_Google_employee_id_100
func (row *sqlRow) getRefLabelFromConstraint(foreignTableInfo *sqlTable,
	constraint *fkConstraint) (string, error) {
	if constraint.foreignIndices == nil {
		foreignKeyColumnNames := make(map[string]string)
		for _, part := range constraint.parts {
			foreignKeyColumnNames[part.columnName] = part.remoteColumnName
		}

		constraint.foreignIndices = getColumnIndices(row.tableInfo,
			func(info *sqlTable, column string) bool {
				_, ok := foreignKeyColumnNames[column]
				return ok
			})

		// replace the column names to be the foreign column names
		for _, colIdx := range constraint.foreignIndices {
			colIdx.name = foreignKeyColumnNames[colIdx.name]
		}
	}

	return createLabel(&ref{
		allColumns:       foreignTableInfo.columns,
		refColumnIndices: constraint.foreignIndices,
		tableName:        foreignTableInfo.tableName,
		colValues:        row.values,
	})
}