标签：统计信息 oracle statistics mysql statistics
我们知道Oracle的统计信息将严重影响CBO对执行计划的选择，针对不同大小的表制定收集规则并且定期执行是非常重要的。Oracle通过如下脚本即可收集统计信息：BEGIN
DBMS_STATS.GATHER_TABLE_STATS(ownname =>'ZBDBA',
tabname =>'TEST',
estimate_percent =>30,
method_opt =>'for all columns size repeat',
no_invalidate =>FALSE,
degree =>8,
cascade =>TRUE);
END;
/ DECLARE
CURSOR STALE_TABLE IS
SELECT OWNER,
SEGMENT_NAME,
CASE
WHEN SIZE_GB < 0.5 THEN
30
WHEN SIZE_GB >= 0.5 AND SIZE_GB < 1 THEN
20
WHEN SIZE_GB >= 1 AND SIZE_GB < 5 THEN
10
WHEN SIZE_GB >= 5 AND SIZE_GB < 10 THEN
5
WHEN SIZE_GB >= 10 THEN
1
END AS PERCENT,
8 AS DEGREE
FROM (SELECT OWNER,
SEGMENT_NAME,
SUM(BYTES / 1024 / 1024 / 1024) SIZE_GB
FROM DBA_SEGMENTS
WHERE OWNER = 'SCOTT'
AND SEGMENT_NAME IN
(SELECT /*+ UNNEST */ DISTINCT TABLE_NAME
FROM DBA_TAB_STATISTICS
WHERE (LAST_ANALYZED IS NULL OR STALE_STATS = 'YES')
AND OWNER = 'SCOTT')
GROUP BY OWNER, SEGMENT_NAME);
BEGIN
DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO;
FOR STALE IN STALE_TABLE LOOP
DBMS_STATS.GATHER_TABLE_STATS(OWNNAME => STALE.OWNER,
TABNAME => STALE.SEGMENT_NAME,
ESTIMATE_PERCENT => STALE.PERCENT,
METHOD_OPT => 'for all columns size repeat',
DEGREE => 8,
GRANULARITY => 'ALL',
CASCADE => TRUE);
END LOOP;
END;
/ # Time: 110923 1:48:17 # User@Host: user1[user1] @ [172.20.6.1] # Thread_id: 10140441 Schema: db1 Last_errno: 0 Killed: 0 # Query_time: 12.277786 Lock_time: 0.000068 Rows_sent: 294 Rows_examined: 294 Rows_affected: 0 Rows_read: 294 # Bytes_sent: 34187 Tmp_tables: 1 Tmp_disk_tables: 0 Tmp_table_sizes: 0 SET timestamp=1316767697; show table status from `db1`;
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标签：统计信息 oracle statistics mysql statistics
原文地址：http://blog.csdn.net/zbdba/article/details/47292595
