Smart Scan是Exadata的主要特性之一,该特性主要依赖于于Exadata Storage Software:
[oracle@database ~]$ sqlplus maclean/maclean SQL*Plus: Release 11.2.0.2.0 Production on Sat Aug 18 22:46:39 2012 Copyright (c) 1982, 2010, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production With the Partitioning, OLAP, Data Mining and Real Application Testing options select a.name,b.value/1024/1024 MB from v$sysstat a , v$mystat b where a.statistic#=b.statistic# and (a.name in ('physical read total bytes','physical write total bytes', 'cell IO uncompressed bytes') or a.name like 'cell phy%'); NAME MB ---------------------------------------------------------------- ---------- physical read total bytes .3984375 physical write total bytes 0 cell physical IO interconnect bytes .3984375 cell physical IO bytes saved during optimized file creation 0 cell physical IO bytes saved during optimized RMAN file restore 0 cell physical IO bytes eligible for predicate offload 0 cell physical IO bytes saved by storage index 0 cell physical IO interconnect bytes returned by smart scan 0 cell IO uncompressed bytes 0 SQL> set linesize 200 pagesize 2000 SQL> set autotrace on; SQL> select /*+ OPT_PARAM('cell_offload_processing' 'false') */ count(*) from sales 2 where time_id between '01-JAN-98' and '31-DEC-98' 3 and amount_sold>=101; COUNT(*) ---------- 30661 Execution Plan ---------------------------------------------------------- Plan hash value: 8150843 ------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 22 | 1238 (2)| 00:00:15 | | 1 | SORT AGGREGATE | | 1 | 22 | | | |* 2 | FILTER | | | | | | |* 3 | TABLE ACCESS STORAGE FULL| SALES | 14685 | 315K| 1238 (2)| 00:00:15 | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter(TO_DATE('01-JAN-98')=101 AND "TIME_ID">='01-JAN-98' AND 3 - filter("AMOUNT_SOLD"》=101 AND "TIME_ID"》='01-JAN-98' AND "TIME_ID"《='31-DEC-98') Note ----- - dynamic sampling used for this statement (level=2) Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 4437 consistent gets 4433 physical reads 0 redo size 424 bytes sent via SQL*Net to client 419 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 1 rows processed SQL> select a.name,b.value/1024/1024 MB 2 from v$sysstat a , v$mystat b 3 where 4 a.statistic#=b.statistic# 5 and (a.name in ('physical read total bytes','physical write total bytes', 6 'cell IO uncompressed bytes') or a.name like 'cell phy%'); NAME MB ---------------------------------------------------------------- ---------- physical read total bytes 35.484375 physical write total bytes 0 cell physical IO interconnect bytes 35.484375 cell physical IO bytes saved during optimized file creation 0 cell physical IO bytes saved during optimized RMAN file restore 0 cell physical IO bytes eligible for predicate offload 0 cell physical IO bytes saved by storage index 0 cell physical IO interconnect bytes returned by smart scan 0 cell IO uncompressed bytes 0 9 rows selected.上面我们使用了exadata核心参数cell_offload_processing=false禁用了smart scan, 下面我们来看看Smart scan的统计表现
select count(*) from sales where time_id between '01-JAN-2003' and '31-DEC-2003' and amount_sold=1; PARSING IN CURSOR #8100532 len=100 dep=0 uid=93 oct=3 lid=93 tim=1345357700828975 hv=1616885803 ad='3f07a6a0' sqlid='7z3cz8ph5zf1b' select count(*) from sales where time_id between '01-JAN-98' and '31-DEC-98' and amount_sold>=101 END OF STMT PARSE #8100532:c=149978,e=1430146,p=271,cr=310,cu=0,mis=1,r=0,dep=0,og=1,plh=8150843,tim=1345357700828975 EXEC #8100532:c=0,e=31,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=8150843,tim=1345357700829041 WAIT #8100532: nam='SQL*Net message to client' ela= 2 driver id=1650815232 #bytes=1 p3=0 obj#=79496 tim=1345357700829074 WAIT #8100532: nam='cell smart table scan' ela= 502 cellhash#=1375519866 p2=0 p3=0 obj#=79496 tim=1345357700830804 WAIT #8100532: nam='cell smart table scan' ela= 20243 cellhash#=1375519866 p2=0 p3=0 obj#=79496 tim=1345357700851709 WAIT #8100532: nam='cell smart table scan' ela= 32442 cellhash#=1375519866 p2=0 p3=0 obj#=79496 tim=1345357700884378 WAIT #8100532: nam='cell smart table scan' ela= 6315 cellhash#=1375519866 p2=0 p3=0 obj#=79496 tim=1345357700891113 WAIT #8100532: nam='cell smart table scan' ela= 17460 cellhash#=1375519866 p2=0 p3=0 obj#=79496 tim=1345357700909251 SQL> select a.name,b.value/1024/1024 MB 2 from v$sysstat a , v$mystat b 3 where 4 a.statistic#=b.statistic# 5 and (a.name in ('physical read total bytes','physical write total bytes', 6 'cell IO uncompressed bytes') or a.name like 'cell phy%'); NAME MB ---------------------------------------------------------------- ---------- physical read total bytes 53.484375 physical write total bytes 0 cell physical IO interconnect bytes .484375 cell physical IO bytes saved during optimized file creation 0 cell physical IO bytes saved during optimized RMAN file restore 0 cell physical IO bytes eligible for predicate offload 53.484375 cell physical IO bytes saved by storage index 0 cell physical IO interconnect bytes returned by smart scan .484375 cell IO uncompressed bytes 53.484375 9 rows selected.
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本文转自maclean_007 51CTO博客,原文链接:
http://blog.51cto.com/maclean/1278446
http://blog.51cto.com/maclean/1278446