分页和buffer_cache关系
今天老大说分页时候会不会cache select语句的信息，然后再到下一页会不会快点，我说不会，我做个试验给他看看
首先清理内存中信息（重启数据库或者手动情况都一样）
格式化trace内容，格式的时候不合并相同的sql，也不查看sys sql
[oracle@DB-87 udump]$ tkprof jscnbi_ora_27002_fenyetest0.trc fenyetest0.sql sys=no aggregate=no
格式化以后的结果如下：
从上面的结果看出，1、2、3次分页过程Fetch disk中内容并没有减少。
后来想想其实根本没有必要这么麻烦，我们只要取0行数据，看buffer_cache有没有就ok了，
结果里面是没有的，说明我的推断是正确的。
首先清理内存中信息（重启数据库或者手动情况都一样）
alter system flush buffer_cache;
做一个10046时间，观察trace内容
set linesize 200
set timing on
alter session set tracefile_identifier='fenyetest0';
alter session set events '10046 trace name context forever,level 4';
variable start_num number;
variable end_num number;
--1. 10000-2000数据
exec :start_num := 10000;
exec :end_num := 20000;
select *
from (
select rownum rn,t.*
from
(select OPERATE_TIME,SERVER_INFO ,ACCESS_IP ,USERID from bi_logfile where OPERATE_TIME>=(sysdate-10)) t
where rownum<:end_num)
where rn >:start_num;
--查看buffer_cache中的内容
SQL> SELECT o.OBJECT_NAME, COUNT(*) NUMBER_OF_BLOCKS
FROM DBA_OBJECTS o, V$BH bh
WHERE o.DATA_OBJECT_ID = bh.OBJD
AND o.OWNER ='JSCNBI'
GROUP BY o.OBJECT_NAME
ORDER BY COUNT(*);
OBJECT_NAME NUMBER_OF_BLOCKS
---------------------------------------- ----------------
BI_LOGFILE_IDX1 128
BI_LOGFILE 1160
--2. 20000-3000数据
exec :start_num := 20000;
exec :end_num := 30000;
select *
from (
select rownum rn,t.*
from
(select OPERATE_TIME,SERVER_INFO ,ACCESS_IP ,USERID from bi_logfile where OPERATE_TIME>=(sysdate-10)) t
where rownum<:end_num)
where rn >:start_num;
--查看buffer_cache中的内容
SQL> SELECT o.OBJECT_NAME, COUNT(*) NUMBER_OF_BLOCKS
FROM DBA_OBJECTS o, V$BH bh
WHERE o.DATA_OBJECT_ID = bh.OBJD
AND o.OWNER ='JSCNBI'
GROUP BY o.OBJECT_NAME
ORDER BY COUNT(*); 2 3 4 5 6
OBJECT_NAME NUMBER_OF_BLOCKS
---------------------------------------- ----------------
BI_LOGFILE_IDX1 197
BI_LOGFILE 1665
--3. 30000-40000数据
exec :start_num := 30000;
exec :end_num := 40000;
select *
from (
select rownum rn,t.*
from
(select OPERATE_TIME,SERVER_INFO ,ACCESS_IP ,USERID from bi_logfile where OPERATE_TIME>=(sysdate-10)) t
where rownum<:end_num)
where rn >:start_num;
--查看buffer_cache中的内容
SQL> SELECT o.OBJECT_NAME, COUNT(*) NUMBER_OF_BLOCKS
FROM DBA_OBJECTS o, V$BH bh
WHERE o.DATA_OBJECT_ID = bh.OBJD
AND o.OWNER ='JSCNBI'
GROUP BY o.OBJECT_NAME
ORDER BY COUNT(*); 2 3 4 5 6
OBJECT_NAME NUMBER_OF_BLOCKS
---------------------------------------- ----------------
BI_LOGFILE_IDX1 222
BI_LOGFILE 1983
alter session set events '10046 trace name context off';
格式化trace内容，格式的时候不合并相同的sql，也不查看sys sql
[oracle@DB-87 udump]$ tkprof jscnbi_ora_27002_fenyetest0.trc fenyetest0.sql sys=no aggregate=no
格式化以后的结果如下：
TKPROF: Release 10.2.0.4.0 - Production on Fri Jul 13 13:57:48 2012
Copyright (c) 1982, 2007, Oracle. All rights reserved.
Trace file: jscnbi_ora_27002_fenyetest0.trc
Sort options: default
********************************************************************************
count = number of times OCI procedure was executed
cpu = cpu time in seconds executing
elapsed = elapsed time in seconds executing
disk = number of physical reads of buffers from disk
query = number of buffers gotten for consistent read
current = number of buffers gotten in current mode (usually for update)
rows = number of rows processed by the fetch or execute call
--------------------------------------------------------------------------------
*** SESSION ID:(309.11) 2012-07-13 13:56:17.864
********************************************************************************
BEGIN :start_num := 10000; END;
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 59
********************************************************************************
BEGIN :end_num := 20000; END;
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 59
********************************************************************************
select *
from (
select rownum rn,t.*
from
(select OPERATE_TIME,SERVER_INFO ,ACCESS_IP ,USERID from bi_logfile where OPERATE_TIME>=(sysdate-10)) t
where rownum<:end_num)
where rn >:start_num
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 668 0.12 0.09 1274 11081 0 9999
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 670 0.12 0.10 1274 11081 0 9999
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 59
Rows Row Source Operation
------- ---------------------------------------------------
9999 VIEW (cr=11081 pr=1274 pw=0 time=84845 us)
19999 COUNT STOPKEY (cr=11081 pr=1274 pw=0 time=81070 us)
19999 TABLE ACCESS BY INDEX ROWID BI_LOGFILE (cr=11081 pr=1274 pw=0 time=81068 us)
19999 INDEX RANGE SCAN BI_LOGFILE_IDX1 (cr=743 pr=127 pw=0 time=676 us)(object id 52405)
********************************************************************************
BEGIN :start_num := 20000; END;
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 59
********************************************************************************
BEGIN :end_num := 30000; END;
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 59
********************************************************************************
select *
from (
select rownum rn,t.*
from
(select OPERATE_TIME,SERVER_INFO ,ACCESS_IP ,USERID from bi_logfile where OPERATE_TIME>=(sysdate-10)) t
where rownum<:end_num)
where rn >:start_num
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 668 0.15 0.11 586 16100 0 9999
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 670 0.15 0.11 586 16100 0 9999
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 59
Rows Row Source Operation
------- ---------------------------------------------------
9999 VIEW (cr=16100 pr=586 pw=0 time=111363 us)
29999 COUNT STOPKEY (cr=16100 pr=586 pw=0 time=120067 us)
29999 TABLE ACCESS BY INDEX ROWID BI_LOGFILE (cr=16100 pr=586 pw=0 time=90064 us)
29999 INDEX RANGE SCAN BI_LOGFILE_IDX1 (cr=781 pr=78 pw=0 time=74 us)(object id 52405)
********************************************************************************
BEGIN :start_num := 30000; END;
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 59
********************************************************************************
BEGIN :end_num := 40000; END;
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 1
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.00 0.00 0 0 0 1
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 59
********************************************************************************
select *
from (
select rownum rn,t.*
from
(select OPERATE_TIME,SERVER_INFO ,ACCESS_IP ,USERID from bi_logfile where OPERATE_TIME>=(sysdate-10)) t
where rownum<:end_num)
where rn >:start_num
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 668 0.13 0.11 345 20964 0 9999
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 670 0.13 0.11 345 20964 0 9999
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 59
Rows Row Source Operation
------- ---------------------------------------------------
9999 VIEW (cr=20964 pr=345 pw=0 time=109073 us)
39999 COUNT STOPKEY (cr=20964 pr=345 pw=0 time=120041 us)
39999 TABLE ACCESS BY INDEX ROWID BI_LOGFILE (cr=20964 pr=345 pw=0 time=120035 us)
39999 INDEX RANGE SCAN BI_LOGFILE_IDX1 (cr=817 pr=16 pw=0 time=109 us)(object id 52405)
********************************************************************************
alter session set events '10046 trace name context off'
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.00 0.00 0 0 0 0
Misses in library cache during parse: 0
Parsing user id: 59
********************************************************************************
OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 10 0.00 0.00 0 0 0 0
Execute 10 0.01 0.01 0 0 0 6
Fetch 2004 0.41 0.32 2205 48145 0 29997
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2024 0.42 0.34 2205 48145 0 30003
Misses in library cache during parse: 7
Misses in library cache during execute: 6
OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 15 0.00 0.00 0 0 0 0
Execute 220 0.06 0.06 0 0 0 0
Fetch 236 0.01 0.01 48 699 0 2077
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 471 0.08 0.08 48 699 0 2077
Misses in library cache during parse: 13
Misses in library cache during execute: 13
10 user SQL statements in session.
220 internal SQL statements in session.
230 SQL statements in session.
********************************************************************************
Trace file: jscnbi_ora_27002_fenyetest0.trc
Trace file compatibility: 10.01.00
Sort options: default
1 session in tracefile.
10 user SQL statements in trace file.
220 internal SQL statements in trace file.
230 SQL statements in trace file.
21 unique SQL statements in trace file.
7288 lines in trace file.
35 elapsed seconds in trace file.
从上面的结果看出，1、2、3次分页过程Fetch disk中内容并没有减少。
后来想想其实根本没有必要这么麻烦，我们只要取0行数据，看buffer_cache有没有就ok了，
--取0行数据
select *
from (
select rownum rn,t.*
from
(select OPERATE_TIME,SERVER_INFO ,ACCESS_IP ,USERID from bi_logfile where OPERATE_TIME>=(sysdate-10)) t
where rownum<2)
where rn >1;
--查看buffer cache中有没有bi_logfile表的数据
SQL> SELECT o.OBJECT_NAME, COUNT(*) NUMBER_OF_BLOCKS
FROM DBA_OBJECTS o, V$BH bh
WHERE o.DATA_OBJECT_ID = bh.OBJD
AND o.OWNER ='JSCNBI'
GROUP BY o.OBJECT_NAME
ORDER BY COUNT(*);
结果里面是没有的，说明我的推断是正确的。