How to apply InnoDB clustered indexes?

InnoDB clustered index is a special type of index that is closely associated with the table data in storage. When creating a table using the InnoDB engine, if a primary key or unique index is not explicitly specified, InnoDB will automatically create a clustered index.

There are several aspects to consider when using InnoDB clustered indexes:

1. Primary key selection: The primary key of a clustered index has a significant impact on the performance of the table, so it is recommended to choose short, unique, and stable columns as the primary key. In general, an auto-incrementing integer column is a good choice because it guarantees the order of new records being inserted, reducing data page splitting and fragmentation.
2. Proper index column selection: The leaf nodes of a clustered index contain the entire data row, so when creating an InnoDB table, it is important to choose the right columns as index columns to meet the needs of queries.
3. Updating a clustered index can be costly in terms of performance because when updating a clustered index column, InnoDB needs to delete the affected data row from its original position and then re-insert it into a new position. This process requires a lot of I/O operations, so it is recommended to minimize frequent updates to clustered index columns when designing table structures.
4. The performance of range queries is enhanced as InnoDB tables store data rows in the order of clustering indexes, allowing range queries (such as using BETWEEN, >, < conditions) to efficiently utilize the order of the clustering index.
5. When using auxiliary indexes (non-clustered indexes) for queries, InnoDB first needs to find the primary key value through the auxiliary index, and then retrieve the corresponding data row based on the primary key value. Therefore, when designing table structures, it is important to choose appropriate auxiliary indexes to improve query performance.

In conclusion, to utilize the InnoDB clustered index effectively, one must carefully select the primary key, index columns, and secondary indexes, avoiding frequent updates to clustered index columns, and maximizing the ordering characteristics of the clustered index to improve query performance.