Re: lifetime of TubleTableSlot* returned by ExecProcNode

After reading the source code for nodeHash.c and tuplesort.c, I decided to create new struct containing MinimumTuple and few members.

I am still wondering in one thing:
typedef struct HashJoinTupleData
{
    struct HashJoinTupleData *next;        /* link to next tuple in same bucket */
    uint32        hashvalue;        /* tuple's hash code */
    /* Tuple data, in MinimalTuple format, follows on a MAXALIGN boundary */
} HashJoinTupleData;

typedef struct
{
    void       *tuple;            /* the tuple proper */
    Datum        datum1;            /* value of first key column */
    bool        isnull1;        /* is first key column NULL? */
    int            tupindex;        /* see notes above */
} SortTuple;

In HashJoinTupleData, the MinimalTupleData is appended at the end of the struct whereas in SortTuple, a pointer to MinimalTupleData is stored in tuple member.
What are the reasons for the difference? And when does one approach is more preferable than another?

Regards,

Bramandia R.