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Overview of Innodb Storage engine Index

The storage engine supports two common indexes: B+ index and Hash index.

Hash index

The Hash index supported by the Innodb storage engine is adaptive. The engine automatically generates the Hash index according to the usage of the table. It cannot artificially interfere with whether to generate the hash index in a table. After Mysql5.5, you can turn off the hash index.

B+ tree index

The Btree index is the most commonly used and effective index in the database at present.

The construction of the B + tree index is similar to that of the binary tree. The data is found fastest according to the key value, and B stands for balance.

The B+ tree index can not find the row of the given key value, but can only find the page where the data row is located, then read the page into the buffer, and finally find the desired data.

The B+ tree index is divided into clustered index and secondary clustered index.

Whether it's a clustered index or a nonclustered index, so the inside is a B + tree, that is, the internal height is balanced.

The difference between a clustered index and a nonclustered index is whether the leaf node stores an entire row of data.

The Innodb storage engine table is the index organization table, similar to the IOT table in oracle, where the data of the table is stored in the order of the primary key, while the clustered index builds a B + tree according to the primary key of the table, and the leaf node stores the whole row of data; in a way, the index is the table, and the table is the index.

Sorting lookups and range lookups for primary keys are very fast.

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