In the process of database query optimization, the index plays a vital role. It can quickly locate the data in the database and improve query speed and efficiency. However, in practical applications, we can easily encounter the problem of not using indexes. This problem cannot be solved by simply adding indexes. This article will give readers a brief introduction to the reasons, impacts and solutions of never indexing in Oracle database.
1. Reasons for not using index
1. Index is not applicable: A basic function of index in database optimization is to optimize query speed, but in some cases, index is not applicable. in the query statement. For example: when querying all the data in the table, the index will not optimize the query speed, but will increase the query time.
2. Index failure: Index failure is one of the main reasons for not using the index. When the data in the database changes, the index may become invalid, resulting in the inability to use the index for optimization during queries. For example: when table data is updated frequently, the index may become invalid, causing queries not to use the index.
3. The amount of data is too large: When the amount of data in the table is large, the index will lose its effect. Because in the case of large amounts of data, the index still needs to scan a large amount of data, making the query slower.
4. Use functions: When the query statement contains a function, Oracle will put the calculation results of the function into the memory for query instead of using the index directly, which will also lead to the problem of not using the index.
2. The impact of not using the index
1. Query speed slows down: Not using the index will cause the query speed to slow down, thus affecting the user experience. If the query takes too long, it is easy for users to lose patience and become dissatisfied with the system.
2. Waste of resources: Not using the index means scanning the entire table, which will require a lot of system resources, including CPU, memory, disk I/O and other resources. For large systems, not indexing will lead to a waste of system resources, thus affecting the stability of the entire system.
3. Low efficiency: When the query efficiency is not high, it will affect the efficiency and performance of the entire system. If query efficiency is consistently low, it may prevent your application from working properly.
3. Solutions without indexing
1. Index optimization: When using indexes, you can improve query efficiency by optimizing the index. Methods to optimize indexes include creating appropriate indexes, modifying index types, or creating joint indexes.
2. Avoid invalid indexes: When the index is invalid, do not force the use of the index. You can find the cause of index failure by analyzing query statements and table structures, thereby avoiding invalid indexes.
3. Optimize query statements: Avoid using functions and expressions in query statements as much as possible. If you must use functions and expressions, consider using built-in functions.
4. Regularly maintain the index: Regularly maintaining the index is an important means to avoid missing the index. Indexes can be maintained through operations such as rebuilding, optimizing, and redistributing the index.
In short, not indexing is an important issue in database optimization. Understanding and solving this problem is crucial to improving the performance and efficiency of the database. By optimizing indexes, avoiding invalid indexes, optimizing query statements, and regularly maintaining indexes, this problem can be effectively solved and the query efficiency and performance of the database can be improved.
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