MySQL索引的B-Tree节点中有多少条目? [英] How many entries are in a node of B-Tree of a MySQL Index?
问题描述
这个在线书籍描述了MySQL如何利用 B-Trees 。时间复杂度取决于每个节点的条目数。
This online book describes how MySQL leverages B-Trees for indexing data. Time complexity depends on the number of entries per node.
MySQL在一个节点中保留了多少条目?
How many entries does MySQL hold in one node?
推荐答案
经验法则:100。
这适用于InnoDB数据BTrees和Index BTrees。但是,它可能相当遥远。
This applies to InnoDB data BTrees and Index BTrees. However, it can be quite far off.
一个极端:节点中只有1个数据记录 - 由于行大小和/或活动(如<$ c) $ C>的DELETE 。另一种情况:具有1条记录的表仍将占用一个完整的16KB块。
One extreme: only 1 data record in a node -- due to large row size and/or activity such as DELETEs
. Another case: A table with 1 record will still occupy a full 16KB block.
其他极端:节点中的500条索引记录 - 由于密钥小而缺乏将删除记录的活动。
Other extreme: 500 index records in a node -- due to small size of key and lack of activity that would have deleted records.
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