比如在排序中，待排序的结构SortTuple中存储的是MinimalTupleData，里面包含有排序需要的值等信息。排好序后，需要将MinimalTupleData再此转换成TupleTableSlot。
转换由函数tts_minimal_store_tuple完成，可以看到MinimalTupleData并没有解析，而是直接放到了MinimalTupleTableSlot的HeapTuple中。
代码语言：javascript复制tts_minimal_store_tuple(TupleTableSlot *slot, MinimalTuple mtup, bool shouldFree)
{
MinimalTupleTableSlot *mslot = (MinimalTupleTableSlot *) slot;
tts_minimal_clear(slot);
slot->tts_flags &= ~TTS_FLAG_EMPTY;
slot->tts_nvalid = 0;
mslot->off = 0;
mslot->mintuple = mtup;
Assert(mslot->tuple == &mslot->minhdr);
mslot->minhdr.t_len = mtup->t_len MINIMAL_TUPLE_OFFSET;
mslot->minhdr.t_data = (HeapTupleHeader) ((char *) mtup - MINIMAL_TUPLE_OFFSET);
/* no need to set t_self or t_tableOid since we won't allow access */
if (shouldFree)
slot->tts_flags |= TTS_FLAG_SHOULDFREE;
else
Assert(!TTS_SHOULDFREE(slot));
}访问行记录值是，需要再将从MinimalTupleData中将列值读取出来，放到TupleTableSlot的tts_values和tts_isnull数组中。这个过程由函数tts_minimal_getsomeattrs完成：
代码语言：javascript复制static void
tts_minimal_getsomeattrs(TupleTableSlot *slot, int natts)
{
MinimalTupleTableSlot *mslot = (MinimalTupleTableSlot *) slot;
slot_deform_heap_tuple(slot, mslot->tuple, &mslot->off, natts);
}重点在slot_deform_heap_tuple函数。
