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In PostgreSQL, tables are stored in heap files in a slotted slotted-page format, which facilitates the storage of variable-length records.

Although this architecture allows tuples to be added or removed from a page, based on PostgreSQL's MVCC approach, these operations do not really delete or replace the old version of the row immediately. Expired tuples can be physically deleted through subsequent commands, creating holes in the page. The strategy of indirectly accessing tuples through an array of row pointers makes these holes reusable.

Most relational databases limit records to no more than a block size, which simplifies buffer management and free space management. Large objects are often stored in a special file (or collection of files) rather than with other (short) attributes of the record. A (logical) pointer to the object is then stored in the record that contains the large object.

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