這個指標為8位元組：4（唯一定位欄位個數）+4（page no）。函式為dict_index_build_node_ptr。僅此記錄，後續研究

```
/**********************************************************************//**
Builds a node pointer out of a physical record and a page number.
@return own: node pointer */
dtuple_t*
dict_index_build_node_ptr(
/*======================*/
	const dict_index_t*	index,	/*!< in: index */
	const rec_t*		rec,	/*!< in: record for which to build node
					pointer */
	ulint			page_no,/*!< in: page number to put in node
					pointer */
	mem_heap_t*		heap,	/*!< in: memory heap where pointer
					created */
	ulint			level)	/*!< in: level of rec in tree:
					0 means leaf level */
{
	dtuple_t*	tuple;
	dfield_t*	field;
	byte*		buf;
	ulint		n_unique;

if (dict_index_is_ibuf(index)) {
		/* In a universal index tree, we take the whole record as
		the node pointer if the record is on the leaf level,
		on non-leaf levels we remove the last field, which
		contains the page number of the child page */

ut_a(!dict_table_is_comp(index->table));
		n_unique = rec_get_n_fields_old(rec);

if (level > 0) {
			ut_a(n_unique > 1);
			n_unique--;
		}
	} else {
		n_unique = dict_index_get_n_unique_in_tree_nonleaf(index);// 唯一定位 到葉子節點的欄位個數
	}

tuple = dtuple_create(heap, n_unique + 1); //建立元組

/* When searching in the tree for the node pointer, we must not do
	comparison on the last field, the page number field, as on upper
	levels in the tree there may be identical node pointers with a
	different page number; therefore, we set the n_fields_cmp to one
	less: */

dtuple_set_n_fields_cmp(tuple, n_unique); //比較欄位為 資料域

dict_index_copy_types(tuple, index, n_unique);  //進行型別複製

buf = static_cast<byte>(mem_heap_alloc(heap, 4)); //分配記憶體

mach_write_to_4(buf, page_no);//寫入 葉子節點page no

field = dtuple_get_nth_field(tuple, n_unique);  //欄位個數  能夠唯一定位的欄位個數
	dfield_set_data(field, buf, 4);//寫入欄位個數

dtype_set(dfield_get_type(field), DATA_SYS_CHILD, DATA_NOT_NULL, 4);

rec_copy_prefix_to_dtuple(tuple, rec, index, n_unique, heap); //複製資料
	dtuple_set_info_bits(tuple, dtuple_get_info_bits(tuple)
			     | REC_STATUS_NODE_PTR);

ut_ad(dtuple_check_typed(tuple));

return(tuple);
}

```</byte>

MySQL:非葉子節點指標

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