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This article mainly introduces the implementation principle of the underlying index of mysql, which has a certain reference value and can be used for reference by friends who need it. I hope you will learn a lot after reading this article. Next, let the editor take you to learn about it.

Data structure and algorithm principle behind MySQL Index

I. definition

Index definition: an index (Index) is a data structure that helps MySQL get data efficiently.

Essence: an index is a data structure.

II. B-Tree

The m-order B-Tree satisfies the following conditions:

1. Each node can have at most m subtrees.

2, the root node, only has at least 2 nodes (either in extreme cases, that is, one root node for a tree, unicellular organisms, that is, roots, leaves, and trees).

3. For non-root and non-leaf nodes, there are at least Ceil (m) subtrees (Ceil means rounded upwards, such as a fifth-order B-tree, where each node has at least three subtrees, that is, at least three forks).

4. The information in the non-leaf node includes [nMagol A0, K1, A1, K2, A2, … , Kn,An], where n represents the number of keywords saved in the node, K is the key and Ki= (select id from cashpool_account_relationship LIMIT 1000000 LIMIT 1) 10

8. Qyoga

1. Does InnoDB support hash index? -- Ma Xin

InnoDB supports hash indexes, but the supported hash indexes are adaptive. The InnoDB storage engine automatically generates hash indexes for tables according to their usage, and cannot artificially interfere with whether or not to generate hash indexes in a table.

2. The leaf node of the InnoDB primary key index contains complete data records, so is the primary key index file larger than the data file? Xu Caihou

1)。 In the Innodb engine, the leaf node in the primary key index contains record data, and the primary key index file is the data file.

2)。 The primary key index size of the data_length data counted in the tables table, and index_length is the size of all secondary indexes (secondary indexes) in this table.

Thank you for reading this article carefully. I hope the editor will share what the underlying principle of the index of mysql is helpful to everyone. At the same time, I also hope that you will support us, pay attention to the industry information channel, and find out if you encounter problems. Detailed solutions are waiting for you to learn!

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