Postgresql扩展页检查-平均bt_metap

Question

我正在使用Postgresql扩展页面检查。

有人能告诉我这些列的含义吗:魔术，版本，根，级别，快速根，bt_metap函数的快速级别。

此信息不在文档1[https://www.postgresql.org/docs/9.6/static/pageinspect.html]中显示。

B-树的高度(从根到叶最远处的节点位置)，是列级吗？

请参阅下面的返回查询，该查询运行于名为idx_l_shipmodelineitem000的索引上。

------------------------------------------------------------------
postgres # SELECT * FROM bt_metap ('idx_l_shipmodelineitem000');
postgres # magic    | version   | root     | level | fastroot | fastlevel
postgres # 340322   | 2         | 41827 | 3       | 41827   | 3

诚挚的问候

Answer 1

src/include/access/nbtree.h：

/*
 * The Meta page is always the first page in the btree index.
 * Its primary purpose is to point to the location of the btree root page.
 * We also point to the "fast" root, which is the current effective root;
 * see README for discussion.
 */

typedef struct BTMetaPageData
{
    uint32      btm_magic;      /* should contain BTREE_MAGIC */
    uint32      btm_version;    /* should contain BTREE_VERSION */
    BlockNumber btm_root;       /* current root location */
    uint32      btm_level;      /* tree level of the root page */
    BlockNumber btm_fastroot;   /* current "fast" root location */
    uint32      btm_fastlevel;  /* tree level of the "fast" root page */
} BTMetaPageData;

所以我建议你读src/后端/access/nbtree/自述