跟大家讲解下有关绑定变量与非绑定变量资源消耗对比,相信小伙伴们对这个话题应该也很关注吧,现在就为小伙伴们说说绑定变量与非绑定变量资源消耗对比,小编也收集到了有关绑定变量与非绑定变量资源消耗对比的相关资料,希望大家看到了会喜欢。
绑定变量和非绑定变量的资源消耗对比 首先初始化数据 Create table tsts as select level as col1 ,rdbms_random.string(p,10) as col2 from dual connect by level = 10000 ; create or replace procedure p1 as rec_tsts%rowtype ; begin for i in1 .. 100
绑定变量和非绑定变量的资源消耗对比首先初始化数据Create table tsts as select level as col1 ,rdbms_random.string(‘p’,10) as col2 from dual connect by level <= 10000 ;
create or replace procedure p1 as
rec_tsts%rowtype ;
begin
for i in1 .. 10000 loop
execute immediate 'select * from tsts where col1='||i into rec_ ;
end loop;
end ;
create or replace procedure p2 as
rec_tsts%rowtype ;
begin
for i in1 .. 10000 loop
execute immediate 'select * from tsts where col1=:1 ' into rec_ using i;
end loop;
end ;
开始比较(使用tom的runstat脚本)exec runstats_pkg.rs_start ;
exec p1 ;
exec runstats_pkg.rs_middle ;
exec p2 ;
exec runstats_pkg.rs_stop(1000) ;
_dexter@FAKE> exec runstats_pkg.rs_start ;
PL/SQL procedure successfully completed.
_dexter@FAKE> exec p1 ;
PL/SQL procedure successfully completed.
_dexter@FAKE> exec runstats_pkg.rs_middle ;
PL/SQL procedure successfully completed.
_dexter@FAKE> exec p2 ;
PL/SQL procedure successfully completed.
_dexter@FAKE> exec runstats_pkg.rs_stop(1000);
Run1 ran in 1163 cpu hsecs
Run2 ran in 64 cpu hsecs
run 1 ran in 1817.19% of the time
Name Run1 Run2 Diff
STAT...recursive cpu usage 1,119 59 -1,060
STAT...DB time 1,150 75 -1,075
STAT...CPU used when call star 1,173 72 -1,101
STAT...CPU used by this sessio 1,172 64 -1,108
STAT...buffer is not pinned co 31,411 30,087 -1,324
STAT...consistent gets 41,986 40,457 -1,529
STAT...consistent gets from ca 41,986 40,457 -1,529
STAT...session logical reads 42,047 40,494 -1,553
STAT...sorts (rows) 1,676 3 -1,673
LATCH.cache buffers chains 66,737 61,883 -4,854
STAT...sql area evicted 9,519 4 -9,515
STAT...session cursor cache hi 360 10,018 9,658
STAT...parse count (hard) 10,053 4 -10,049
STAT...enqueue releases 10,053 4 -10,049
STAT...enqueue requests 10,053 4 -10,049
STAT...parse count (total) 10,057 4 -10,053
LATCH.enqueue hash chains 20,379 110 -20,269
STAT...recursive calls 41,827 10,157 -31,670
LATCH.shared pool simulator 38,862 40 -38,822
LATCH.shared pool 455,526 10,683 -444,843
LATCH.row cache objects 513,487 441 -513,046
STAT...logical read bytes from 344,449,024331,726,848 -12,722,176
Run1 latches total versus runs -- difference andpct
Run1 Run2 Diff Pct
1,097,601 74,729 -1,022,872 1,468.78%
PL/SQL procedure successfully completed.
分析可以看到资源使用相差是非常巨大的。我们示例中的sql语句是典型的应用在oltp系统中的,可以看到使用绑定变量消耗更少的资源。我们观察相差比较大的事件。执行可以完全肯定,绑定变量优于非绑定变量。主要由于下面几个相差较大的事件影响。
Binding
No binding
Desc
session cursor cache hits
10,018
360
cursor命中率
sql area evicted
4
9,519
Shared pool 不足引起的ageout
parse count (hard)
4
10,053
硬解析
enqueue releases
4
10,053
Enqueue锁释放
enqueue requests
4
10,053
Enqueue锁请求
parse count (total)
4
10,057
解析总次数
enqueue hash chains
110
20,379
获取hash chain次数
recursive calls
10,157
41,827
读取数据字典信息可能引发recursive calls
shared pool simulator
40
38,862
Advice信息收集
shared pool
10,683
455,526
Shared pool使用
row cache objects
441
513,487
硬解析会读取更多的统计信息
logical read byte
331,726,848
344,449,024
逻辑读
可以看到,因为硬解析,oracle数据库优化器需要重新对语句进行优化操作,需要获取更多的latch并且执行更多的操作,而且对于oltp系统中的语句,优化期间所做的操作甚至比查询数据需要更多的时间,所以在OLTP系统中,更多的使用绑定变量,是非常有必要的。
附录:tom runstat 脚本的使用
1. 创建临时表create or replace view statsas select 'STAT...' || a.name name, b.valuefrom v$statname a, v$mystat bwhere a.statistic# = b.statistic#union allselect 'LATCH.' || name, getsfrom v$latchunion allselect 'STAT...Elapsed Time', hsecs from v$timer;需要授权相应的视图权限grant select on v_$statname to &&username ;grant select on v_$mystat to &&username ;grant select on v_$latch to &&username ;grant select on v_$timer to &&username ;2. 创建临时表create global temporary table run_stats( runid varchar2(15),name varchar2(80),value int )on commit preserve rows;3. 创建相应的runstat包create or replace package runstats_pkg asprocedure rs_start;procedure rs_middle;procedure rs_stop(p_difference_threshold in number default 0);end;/create or replace package body runstats_pkg asg_start number;g_run1 number;g_run2 number;procedure rs_start isbegindelete from run_stats;insert into run_statsselect 'before', stats.* from stats;g_start := dbms_utility.get_cpu_time;end;procedure rs_middle isbeging_run1 := (dbms_utility.get_cpu_time - g_start);insert into run_statsselect 'after 1', stats.* from stats;g_start := dbms_utility.get_cpu_time;end;procedure rs_stop(p_difference_threshold in number default 0) isbeging_run2 := (dbms_utility.get_cpu_time - g_start);dbms_output.put_line('Run1 ran in ' || g_run1 || ' cpu hsecs');dbms_output.put_line('Run2 ran in ' || g_run2 || ' cpu hsecs');if (g_run2 0) thendbms_output.put_line('run 1 ran in ' ||round(g_run1 / g_run2 * 100, 2) ||'% of the time');end if;dbms_output.put_line(chr(9));insert into run_statsselect 'after 2', stats.* from stats;dbms_output.put_line(rpad('Name', 30) || lpad('Run1', 12) ||lpad('Run2', 12) || lpad('Diff', 12));for x in (select rpad(a.name, 30) ||to_char(b.value - a.value, '999,999,999') ||to_char(c.value - b.value, '999,999,999') ||to_char(((c.value - b.value) - (b.value - a.value)),'999,999,999') datafrom run_stats a, run_stats b, run_stats cwhere a.name = b.nameand b.name = c.nameand a.runid = 'before'and b.runid = 'after 1'and c.runid = 'after 2'and abs((c.value - b.value) - (b.value - a.value)) >p_difference_thresholdorder by abs((c.value - b.value) - (b.value - a.value))) loopdbms_output.put_line(x.data);end loop;dbms_output.put_line(chr(9));dbms_output.put_line('Run1 latches total versus runs -- difference and pct');dbms_output.put_line(lpad('Run1', 12) || lpad('Run2', 12) ||lpad('Diff', 12) || lpad('Pct', 10));for x in (select to_char(run1, '999,999,999') ||to_char(run2, '999,999,999') ||to_char(diff, '999,999,999') ||to_char(round(run1 /decode(run2, 0, to_number(0), run2) * 100,2),'99,999.99') || '%' datafrom (select sum(b.value - a.value) run1,sum(c.value - b.value) run2,sum((c.value - b.value) - (b.value - a.value)) difffrom run_stats a, run_stats b, run_stats cwhere a.name = b.nameand b.name = c.nameand a.runid = 'before'and b.runid = 'after 1'and c.runid = 'after 2'and a.name like 'LATCH%')) loopdbms_output.put_line(x.data);end loop;end;end;/4. 用法exec runstats_pkg.rs_start;p1exec runstats_pkg.rs_middle;p2exec runstats_pkg.rs_stop(1000);示例:dexter@REPO>exec runstats_pkg.rs_start;PL/SQL 过程已成功完成。dexter@REPO>delete from t1 ;已删除 1 行。dexter@REPO>exec runstats_pkg.rs_middle;PL/SQL 过程已成功完成。dexter@REPO>insert into t1 select level from dual connect by level exec runstats_pkg.rs_stop(100);Run1 ran in 1 cpu hsecsRun2 ran in 4 cpu hsecsrun 1 ran in 25% of the timeName Run1 Run2 DiffLATCH.session idle bit 331 207 -124STAT...redo entries 15 167 152LATCH.SQL memory manager worka 1,012 807 -205STAT...db block changes 77 300 223LATCH.enqueue hash chains 1,035 794 -241LATCH.cache buffers chains 2,182 2,425 243STAT...db block gets 60 304 244STAT...db block gets from cach 60 304 244STAT...session logical reads 89 374 285LATCH.shared pool 1,016 515 -501STAT...Elapsed Time 4,370 3,681 -689LATCH.row cache objects 2,063 1,082 -981STAT...undo change vector size 3,908 29,856 25,948STAT...physical read bytes 8,192 40,960 32,768STAT...physical read total byt 8,192 40,960 32,768STAT...cell physical IO interc 8,192 40,960 32,768STAT...session uga memory max 123,512 65,488 -58,024STAT...session uga memory 65,488 0 -65,488STAT...file io wait time 8,767 113,342 104,575STAT...redo size 5,220 167,168 161,948STAT...logical read bytes from 729,088 3,063,808 2,334,720Run1 latches total versus runs -- difference and pctRun1 Run2 Diff Pct11,252 8,792 -2,460 127.98%PL/SQL 过程已成功完成。来源:php中文网