oracle查询某数据库用户下哪些表的索引没有被使用到？

1. 开启所有索引的监控

sql 复制代码

-- 为指定用户下的所有索引开启监控
BEGIN
  FOR idx IN (SELECT owner, index_name FROM dba_indexes WHERE owner = 'YOUR_SCHEMA') 
  LOOP
    EXECUTE IMMEDIATE 'ALTER INDEX ' || idx.owner || '.' || idx.index_name || ' MONITORING USAGE';
  END LOOP;
END;
/

2. 运行一段时间后检查使用情况

sql 复制代码

-- 查看监控结果（需要DBA权限）
SELECT 
    u.owner,
    u.index_name,
    i.table_name,
    u.monitoring,
    u.used,
    u.start_monitoring,
    u.end_monitoring,
    i.index_type,
    i.uniqueness,
    i.status
FROM v$object_usage u
JOIN dba_indexes i ON u.index_name = i.index_name AND u.owner = i.owner
WHERE u.owner = 'YOUR_SCHEMA'
  AND u.used = 'NO'  -- 未使用的索引
ORDER BY i.table_name, u.index_name;

3. 关闭监控

sql 复制代码

-- 监控完成后关闭监控
BEGIN
  FOR idx IN (SELECT owner, index_name FROM dba_indexes WHERE owner = 'YOUR_SCHEMA') 
  LOOP
    EXECUTE IMMEDIATE 'ALTER INDEX ' || idx.owner || '.' || idx.index_name || ' NOMONITORING USAGE';
  END LOOP;
END;
/

4.查询AWR中索引使用统计（需要AWR许可）--推荐使用，可以获取哪些索引使用频繁最高，哪些索引使用频繁最低，适用于生产慢SQL优化

sql 复制代码

-- 查看过去N天内索引在AWR中的使用情况
SELECT 
    d.object_owner,
    d.object_name as index_name,
    t.table_name,
    COUNT(DISTINCT d.sql_id) as sql_count,
    COUNT(*) as plan_line_count,
    MIN(d.timestamp) as first_seen,
    MAX(d.timestamp) as last_seen
FROM dba_hist_sql_plan d
JOIN dba_indexes i ON d.object_owner = i.owner AND d.object_name = i.index_name
JOIN dba_tables t ON i.table_owner = t.owner AND i.table_name = t.table_name
WHERE d.object_owner = 'YOUR_SCHEMA'
  AND d.object_type = 'INDEX'
  AND d.timestamp > SYSDATE - 30  -- 最近30天
GROUP BY d.object_owner, d.object_name, t.table_name
ORDER BY sql_count ASC;  -- 使用次数少的排在前面

5.从未在AWR中出现的索引（可能从未使用）--推荐使用，用于优化生产无效索引

sql 复制代码

-- 找出从未在AWR执行计划中出现的索引
SELECT 
    i.owner,
    i.index_name,
    i.table_name,
    i.index_type,
    i.uniqueness,
    i.status,
    i.num_rows,
    i.leaf_blocks
FROM dba_indexes i
LEFT JOIN (
    SELECT DISTINCT object_owner, object_name
    FROM dba_hist_sql_plan
    WHERE object_type = 'INDEX'
      AND timestamp > SYSDATE - 90  -- 最近90天
) p ON i.owner = p.object_owner AND i.index_name = p.object_name
WHERE i.owner = 'YOUR_SCHEMA'
  AND p.object_name IS NULL  -- 从未出现在AWR中
  AND i.index_type NOT IN ('LOB', 'DOMAIN')  -- 排除特殊类型索引
ORDER BY i.table_name, i.index_name;