Thanks to Daniel Verite, nice answer, really helpful :) It summarizes what I have read in the doc and blogs.
What about updates where the bytea do not changed. Does a new copy of the bytea will be made in the toast table or new row will point to the original bytea? > https://www.postgresql.org/docs/current/storage-toast.html says > The TOAST management code is triggered only when a row value to be stored in > a table is wider than TOAST_TUPLE_THRESHOLD bytes (normally 2 kB). The TOAST > code will compress > and/or move field values out-of-line until the row value is shorter than > TOAST_TUPLE_TARGET bytes (also normally 2 kB, adjustable) or no more gains > can be had. During an UPDATE > operation, values of unchanged fields are normally preserved as-is; so an > UPDATE of a row with out-of-line values incurs no TOAST costs if none of the > out-of-line values change. Does it means, no incurs cost to generate the out of line toast, but that a copy of the bytea is still made for the new line? Jean-Marc Lessard Administrateur de base de données / Database Administrator Ultra Electronics Forensic Technology Inc. T +1 514 489 4247 x4164 www.ultra-forensictechnology.com<http://www.ultra-forensictechnology.com>
