Oracle统计信息相关

以下是检查 Oracle 统计信息更新时间的常用方法：

1. 查看表级统计信息更新时间

-- 查看用户表统计信息
SELECT table_name, num_rows,last_analyzed,TO_CHAR(last_analyzed, 'YYYY-MM-DD HH24:MI:SS') as analyze_time,stale_stats
FROM user_tables
WHERE table_name = '表名'
ORDER BY last_analyzed DESC;-- 查看所有表（含系统时间戳）
SELECT owner,table_name,num_rows,blocks,last_analyzed,ROUND((SYSDATE - last_analyzed) * 24) as hours_ago
FROM dba_tables
WHERE owner = '用户名'
ORDER BY last_analyzed;

2. 查看索引统计信息更新时间

-- 查看索引统计信息
SELECT index_name,table_name,last_analyzed,num_rows,distinct_keys,TO_CHAR(last_analyzed, 'YYYY-MM-DD HH24:MI:SS') as analyze_time
FROM user_indexes
WHERE table_name = '表名'
ORDER BY last_analyzed DESC;-- 查看所有索引统计信息
SELECT owner,index_name,table_name,last_analyzed,DENSE_RANK() OVER (PARTITION BY owner ORDER BY last_analyzed DESC) as rank
FROM dba_indexes
WHERE owner = '用户名'
ORDER BY last_analyzed DESC;

3. 查看列统计信息（直方图）

-- 查看列的统计信息
SELECT table_name,column_name,num_distinct,num_nulls,last_analyzed,histogram
FROM user_tab_columns
WHERE table_name = '表名'
ORDER BY last_analyzed DESC;-- 查看直方图统计信息
SELECT table_name,column_name,endpoint_number,endpoint_value,last_analyzed
FROM user_tab_histograms
WHERE table_name = '表名'
ORDER BY table_name, column_name, endpoint_number;

4. 查看分区统计信息

-- 查看分区表统计信息
SELECT table_name,partition_name,num_rows,last_analyzed,ROUND((SYSDATE - last_analyzed) * 24, 2) as hours_ago
FROM user_tab_partitions
WHERE table_name = '表名'
ORDER BY last_analyzed DESC;-- 查看子分区统计信息
SELECT table_name,partition_name,subpartition_name,num_rows,last_analyzed
FROM user_tab_subpartitions
WHERE table_name = '表名'
ORDER BY last_analyzed DESC;

5. 统计信息是否过期（STALE_STATS）

-- 查看过期统计信息
SELECT owner,table_name,stale_stats,last_analyzed,CASE WHEN stale_stats = 'YES' THEN '统计信息过期'WHEN stale_stats = 'NO' THEN '统计信息有效'ELSE '未分析'END as status
FROM dba_tab_statistics
WHERE owner = '用户名'
AND stale_stats = 'YES'  -- 只看过期的
ORDER BY last_analyzed;-- 查看所有表状态
SELECT owner,COUNT(*) as total_tables,SUM(CASE WHEN stale_stats = 'YES' THEN 1 ELSE 0 END) as stale_tables,SUM(CASE WHEN last_analyzed IS NULL THEN 1 ELSE 0 END) as never_analyzed
FROM dba_tab_statistics
WHERE owner = '用户名'
GROUP BY owner;

6. 汇总脚本

-- 统计信息健康度报告
SELECT owner,table_name,num_rows,blocks,last_analyzed,stale_stats,CASE WHEN last_analyzed IS NULL THEN '从未分析'WHEN stale_stats = 'YES' THEN '已过期'WHEN (SYSDATE - last_analyzed) > 7 THEN '超过7天未更新'WHEN (SYSDATE - last_analyzed) > 1 THEN '超过1天未更新'ELSE '最近更新'END as analyze_status,ROUND((SYSDATE - last_analyzed) * 24, 2) as hours_since_analyze
FROM dba_tab_statistics
WHERE owner = '用户名'
AND (stale_stats = 'YES' OR last_analyzed IS NULL OR (SYSDATE - last_analyzed) > 1)
ORDER BY last_analyzed NULLS FIRST;

7. 检查统计信息收集任务

-- 查看自动统计信息收集窗口
SELECT window_name,REPLACE(REPLACE(resource_plan, '<![CDATA[', ''), ']]>', '') as resource_plan,enabled,next_start_date,repeat_interval
FROM dba_scheduler_windows
WHERE window_name LIKE 'MON%' OR window_name LIKE 'WEE%'
ORDER BY window_name;-- 查看统计信息收集作业状态
SELECT job_name,enabled,state,next_run_date,repeat_interval
FROM dba_scheduler_jobs
WHERE job_name LIKE '%GATHER%STATS%';-- 查看最近执行的统计信息收集任务
SELECT job_name,job_action,run_date,SUCC_DONE
FROM dba_scheduler_job_run_details
WHERE job_name LIKE '%GATHER%STATS%'
ORDER BY run_date DESC
FETCH FIRST 20 ROWS ONLY;

8. 检查统计信息锁

-- 查看表是否被锁定统计信息
SELECT owner,table_name,stattype_locked
FROM dba_tab_statistics
WHERE owner = '用户名'
AND stattype_locked IS NOT NULL;-- 查看索引是否被锁定统计信息
SELECT owner,index_name,table_name,stattype_locked
FROM dba_ind_statistics
WHERE owner = '用户名'
AND stattype_locked IS NOT NULL;

9. 对比不同时间点的统计信息

-- 对比历史统计信息（使用AWR）
SELECT snap_id,begin_interval_time,end_interval_time,table_name,num_rows
FROM dba_hist_tab_stat_history
WHERE owner = '用户名'
AND table_name = '表名'
ORDER BY snap_id DESC;

10. 实用诊断脚本

-- 完整的统计信息诊断报告
SELECT '表统计信息' as type,owner,table_name as object_name,last_analyzed,stale_stats,ROUND((SYSDATE - last_analyzed) * 24, 2) as hours_ago
FROM dba_tab_statistics
WHERE owner = '用户名'
AND (stale_stats = 'YES' OR last_analyzed IS NULL)UNION ALLSELECT '索引统计信息' as type,owner,index_name as object_name,last_analyzed,'' as stale_stats,ROUND((SYSDATE - last_analyzed) * 24, 2) as hours_ago
FROM dba_ind_statistics
WHERE owner = '用户名'
AND last_analyzed IS NULLORDER BY hours_ago DESC NULLS FIRST;

11. 快速检查特定表

-- 一键查看表的所有统计信息
SELECT t.table_name,t.num_rows as table_rows,t.blocks as table_blocks,t.last_analyzed as table_analyzed,t.stale_stats as table_stale,COUNT(i.index_name) as index_count,MAX(i.last_analyzed) as latest_index_analyzed
FROM user_tables t
LEFT JOIN user_indexes i ON t.table_name = i.table_name
WHERE t.table_name = '表名'
GROUP BY t.table_name, t.num_rows, t.blocks, t.last_analyzed, t.stale_stats;

12. 检查统计信息收集配置

-- 查看统计信息收集参数
SELECT name, value, description
FROM v$parameter
WHERE name IN ('optimizer_use_pending_statistics','optimizer_dynamic_sampling','optimizer_capture_sql_plan_baselines','statistics_level','preferred_aggregate_function'
);-- 查看数据库统计信息
SELECT * FROM dba_optstat_operations
ORDER BY end_time DESC
FETCH FIRST 10 ROWS ONLY;

常用场景示例

场景1：检查未更新统计信息的表

SELECT owner, table_name, last_analyzed
FROM dba_tables
WHERE owner = '用户名'
AND (last_analyzed IS NULL OR last_analyzed < SYSDATE - 7)
ORDER BY last_analyzed NULLS FIRST;

场景2：检查大表的统计信息

SELECT owner, table_name, num_rows, last_analyzed
FROM dba_tables
WHERE owner = '用户名'
AND num_rows > 1000000
ORDER BY num_rows DESC;

场景3：SQL执行计划改变前后的对比

-- 记录当前统计信息时间
SELECT table_name, last_analyzed 
FROM user_tables 
WHERE table_name IN ('表1', '表2');-- 重新收集统计信息后对比

更新统计信息

-- 收集表统计信息
EXEC DBMS_STATS.GATHER_TABLE_STATS(ownname => '用户名', tabname => '表名');-- 收集所有对象统计信息
EXEC DBMS_STATS.GATHER_SCHEMA_STATS(ownname => '用户名');-- 收集数据库统计信息
EXEC DBMS_STATS.GATHER_DATABASE_STATS();-- 收集统计信息并查看进展
EXEC DBMS_STATS.GATHER_TABLE_STATS(ownname => '用户名',tabname => '表名',estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE,method_opt => 'FOR ALL COLUMNS SIZE AUTO',cascade => TRUE
);

关键点：

• last_analyzed 越新越好
• stale_stats = 'YES' 表示可能过期
• 大表建议开启自动统计信息收集
• 被锁定的统计信息需要手动处理