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.