Analysis of index duplication in Oracle database

Analysis of index duplication in Oracle database

Index plays a vital role in the database. It can improve the efficiency of queries and speed up data retrieval. However, in actual applications, index duplication sometimes occurs, which affects database performance and query efficiency. This article will introduce how to analyze index duplication in Oracle database and demonstrate it through specific code examples.

1. The impact of duplicate indexes

Duplicate indexes will cause a waste of storage space in the database, increase the cost of data update, and reduce the performance of the database. When there are too many duplicate indexes in a database, query performance may be affected because the database needs to maintain these duplicate indexes, causing queries to slow down. Therefore, timely troubleshooting and cleaning up index duplication is an important part of database optimization.

2. Methods to analyze index duplication

In the Oracle database, you can view the index information through the system views dba_indexes and dba_ind_columns to find out whether there are duplicate indexes. The following is a simple query statement that can list all indexes in the database and their column information:

SELECT i.index_name, i.table_name, LISTAGG(i.column_name, ', ') WITHIN GROUP (ORDER BY i.column_position) AS index_columns
FROM dba_ind_columns i
JOIN dba_indexes idx ON i.index_name = idx.index_name
AND i.table_name = idx.table_name
GROUP BY i.index_name, i.table_name;

Run the above code to get the index and its corresponding column information. By observing the results, you can initially judge whether There are duplicate indexes.

3. Specific code examples

In order to demonstrate the situation of index duplication, we first create a test table and create two identical indexes on the table. Then use the above query statement to view the index information.

-- 创建测试表
CREATE TABLE test_table (
    id NUMBER,
    name VARCHAR2(50)
);

-- 在表上创建两个相同的索引
CREATE INDEX idx_test_table_id ON test_table(id);
CREATE INDEX idx_test_table_id_2 ON test_table(id);

-- 查询索引信息
SELECT i.index_name, i.table_name, LISTAGG(i.column_name, ', ') WITHIN GROUP (ORDER BY i.column_position) AS index_columns
FROM dba_ind_columns i
JOIN dba_indexes idx ON i.index_name = idx.index_name
AND i.table_name = idx.table_name
WHERE idx.table_name = 'TEST_TABLE'
GROUP BY i.index_name, i.table_name;

Run the above code, you can see that the two indexes idx_test_table_id and idx_test_table_id_2 are created based on the id column of the test_table table, which shows that there are duplicate indexes.

4. Cleaning index duplication

It is very important to clean up index duplication. You can delete duplicate indexes through the following code:

-- 删除重复的索引
DROP INDEX idx_test_table_id_2;

After deleting duplicate indexes, you can Run the query statement again to verify the index situation and ensure that there are no duplicate indexes in the database.

Summary

Index duplication is a key issue that needs to be paid attention to in database performance optimization. Timely troubleshooting and clearing of index duplication can improve the query efficiency and performance of the database. By analyzing index information, finding duplicate indexes, and cleaning up redundant indexes, you can effectively avoid the performance impact caused by duplicate indexes. I hope the above content will be helpful to you in analyzing the duplication of Oracle database indexes.

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