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本篇文章为大家展示了 MySQL 的非叶子节点指针是什么，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。
这个指针为 8 字节：4（唯一定位字段个数）+4（page no）。函数为 dict_index_build_node_ptr。仅此记录，后续研究
/**********************************************************************//**
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 到叶子节点的字段个数
}
tuple = dtuple_create(heap, n_unique + 1); // 建立元组
/* 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); // 比较字段为 数据域
dict_index_copy_types(tuple, index, n_unique); // 进行类型复制
buf = static_cast byte* (mem_heap_alloc(heap, 4)); // 分配内存
mach_write_to_4(buf, page_no);// 写入 叶子节点 page no
field = dtuple_get_nth_field(tuple, n_unique); // 字段个数 能够唯一定位的字段个数
dfield_set_data(field, buf, 4);// 写入字段个数
dtype_set(dfield_get_type(field), DATA_SYS_CHILD, DATA_NOT_NULL, 4);
rec_copy_prefix_to_dtuple(tuple, rec, index, n_unique, heap); // 复制数据
dtuple_set_info_bits(tuple, dtuple_get_info_bits(tuple)
| REC_STATUS_NODE_PTR);
ut_ad(dtuple_check_typed(tuple));
return(tuple);
}上述内容就是 MySQL 的非叶子节点指针是什么，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注丸趣 TV 行业资讯频道。
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