Variable-length Records

Variable Length Records

• These occur in databases in several ways. The data fields might be heterogenous, and there may be variations of size between even the same datatype.
• Attributes are still stored in order.

Slotted Page Structure

• In this structure, there are two segments - the header and the records.
• The header tells us about a record as a (offset, length) tuple.
• Records may be rearranged to ensure they are contiguous with minimal empty space between them. The header will be rearranged according to this.
• A pointer to the entry will not point to a record, but its header.
• The end of the header section has a single number, which tells the amount of free space in the block.