Koichi Suzuki <suzukikui@nttdata.co.jp> writes:
> I need to know where such "lock marks" are stored in the source level.
A row lock is represented by storing the locking transaction's ID in
xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. The bit is
needed to distinguish this from the case where the transaction is
deleting the tuple.
regards, tom lane