typedef HeapTupleData *HeapTuple;

typedef struct HeapTupleData
{
  uint32           t_len;  // length of *t_data 
  ItemPointerData t_self;  // SelfItemPointer 
  Oid         t_tableOid;  // table the tuple came from 
  HeapTupleHeader t_data;  // -> tuple header and data 
} HeapTupleData;