TOAST Storage Strategies
Introduction As mentioned previously regarding storing data into HEAP, Postgres enforces a strict rule where a Row/Tuple must fit entirely within a single Page (8KB) and cannot overflow into another Page. The maximum size of a Row ranges from approximately 2KB to 8KB. If you intentionally insert a very long TEXT value or a file of several MBs into a row, an 8KB Page cannot accommodate such large data, prompting Postgres to trigger a mechanism called TOAST (The Oversized-Attribute Storage Technique). When you insert a data row whose size exceeds the allowed threshold (typically around 2KB), Postgres will not insert the entire row into the main HEAP. It executes the following three steps: Data compression: First, Postgres attempts to compress the oversized data to see if it fits within the 8KB Page. If successful, it is still inserted into the main HEAP. Chunking and moving to TOAST: If the data remains too large after compression, Postgres splits that 5MB data into multiple small chunks...