What does "tuple (0,79)" in postgres log file mean when a deadlock happened?
This is the data type of the system column ctid. A tuple ID is a pair (block number, tuple index within block) that identifies the physical location of the row within its table.
read https://www.postgresql.org/docs/current/static/datatype-oid.html
It means block number 0, row index 79
also read http://rachbelaid.com/introduction-to-postgres-physical-storage/
also run SELECT id,ctid FROM account where id=$1 with right $1 to check out...