MySQL™: The World’s Most Popular Open Source Database 183 InnoDB Row Structure • Records with variable (dynamic) size Record hdr Trx ID Roll ptr Fld ptrs Field values ... Field values • Record header (6 B, ptr to next record, no of fields) • Transaction ID (6 B, timestamp) • Roll pointer (7 B, points to previous version of record) • Field pointers (1-2 B / field) – Start position of field within record – 2 bytes if more than 255 fields • Out-of-page pointers if record size > page size/2 (8 kB) Copyright 2003 MySQL AB