64. SQL> select client_name, status
2 from DBA_AUTOTASK_CLIENT;
CLIENT_NAME STATUS
------------------------------------ --------
auto optimizer stats collection ENABLED
auto space advisor ENABLED
sql tuning advisor ENABLED
64
120. select * insert into PEOPLE
from PEOPLE select * from ...
select ...
from PEOPLE,
DEPT
where ...
SQL> begin
2 dbms_stats.gather_table_stats(
3 'DEMO',
4 'PEOPLE);
5 end;
6 /
declare
delete from T v people.name%type;
where X in begin
( select PID ...
from PEOPLE )
120
125. SQL> desc DBMS_STATS
PROCEDURE GATHER_TABLE_STATS
Argument Name Type In/Out Default?
----------------------- -------------- ------ --------
OWNNAME VARCHAR2 IN
TABNAME VARCHAR2 IN
PARTNAME VARCHAR2 IN DEFAULT
ESTIMATE_PERCENT NUMBER IN DEFAULT
BLOCK_SAMPLE BOOLEAN IN DEFAULT
METHOD_OPT VARCHAR2 IN DEFAULT
DEGREE NUMBER IN DEFAULT
GRANULARITY VARCHAR2 IN DEFAULT
CASCADE BOOLEAN IN DEFAULT
STATTAB VARCHAR2 IN DEFAULT
STATID VARCHAR2 IN DEFAULT
STATOWN VARCHAR2 IN DEFAULT
NO_INVALIDATE BOOLEAN IN DEFAULT
STATTYPE VARCHAR2 IN DEFAULT
FORCE BOOLEAN IN DEFAULT
125
129. SQL> select
2 x.ksppinm name,
3 y.kspftctxvl value
4 from
5 sys.x$ksppi x,
6 sys.x$ksppcv2 y
7 where
8 x.indx+1 = y.kspftctxpn and
9 x.ksppinm = '_optimizer_invalidation_period'
NAME VALUE
------------------------------ ------------
_optimizer_invalidation_period 18000
129
130. select * insert into PEOPLE
from PEOPLE select * from ...
select ...
from PEOPLE,
DEPT
where ...
SQL> exec dbms_stats.gather_table_stats(
user,'PEOPLE');
declare
delete from T v people.name%type;
where X in begin
( select PID ...
from PEOPLE )
130
215. SQL> select * from t where dte = '12-AUG-2011';
----------------------------------------------------
| Id | Operation | Name | Rows |
----------------------------------------------------
| 0 | SELECT STATEMENT | | 2381 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 2381 |
|* 2 | INDEX RANGE SCAN | IX | 2381 |
----------------------------------------------------
216. SQL> select * from t where dte = '14-AUG-2011';
----------------------------------------------------
| Id | Operation | Name | Rows |
----------------------------------------------------
| 0 | SELECT STATEMENT | | 1 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 1 |
|* 2 | INDEX RANGE SCAN | IX | 1 |
----------------------------------------------------
231. SQL> desc VEHICLE
Name Null? Type
-------------------------- -------- -------------
ID NUMBER
MAKE VARCHAR2(6)
MODEL VARCHAR2(6)
SQL> select count(*)
2 from VEHICLE;
COUNT(*)
------------
2,157,079
231
231
273. SQL> desc DBA_TABLES
Name Null? Type
----------------------------- -------- -------------
OWNER NOT NULL VARCHAR2(30)
TABLE_NAME NOT NULL VARCHAR2(30)
COLUMN_NAME NOT NULL VARCHAR2(30)
...
NUM_ROWS NUMBER
273
274. SQL> desc DBA_TAB_COLS
Name Null? Type
----------------------------- -------- -------------
OWNER NOT NULL VARCHAR2(30)
TABLE_NAME NOT NULL VARCHAR2(30)
COLUMN_NAME NOT NULL VARCHAR2(30)
...
NUM_DISTINCT NUMBER
LOW_VALUE RAW(32)
HIGH_VALUE RAW(32)
...
274
275. SQL> desc PEOPLE
Name Null? Type
----------------------------- -------- -------------
PID NUMBER
GENDER CHAR(1)
NAME VARCHAR2(47)
AGE NUMBER
DEATH_RATE NUMBER
275
276. SQL> alter session set sql_true = true;
Session altered.
SQL> begin
2 dbms_stats.gather_table_stats(
3 'DEMO',
4 'PEOPLE);
5 end;
6 /
276
293. SQL> set serverout on
SQL> declare
2 type t_bucket is table of varchar2(1);
3 l_synopsis t_bucket;
4 l_splits number := 0;
5 l_hash int;
6 l_min_val int := 0;
7 l_synopsis_size int := 16;
8 begin
9 for i in ( select single_char from one_pass ) loop
10 l_hash := ascii(i.single_char);
11
12 if l_synopsis.count = l_synopsis_size then
13 l_min_val :=
14 case
15 when l_min_val = 0 then 64
16 when l_min_val = 64 then 96
17 when l_min_val = 96 then 112
18 when l_min_val = 112 then 120
19 end;
20 l_splits := l_splits + 1;
293
294. 22
23 for j in 1 .. l_min_val loop
24 if l_synopsis.exists(j) then
25 l_synopsis.delete(j);
26 end if;
27 end loop;
28 end if;
29
30 if l_hash > l_min_val then
31 l_synopsis(l_hash) := 'Y';
32 end if;
33 end loop;
34 dbms_output.put_line(l_synopsis.count *
35 power(2,l_splits));
36 end;
37 /
Splitting, keeping entries above 64
Splitting, keeping entries above 96
Splitting, keeping entries above 112
88
294
313. SQL> desc SYS.COL_USAGE$
Name Null? Type
----------------------- -------- ---------
OBJ# NUMBER
INTCOL# NUMBER
EQUALITY_PREDS NUMBER
EQUIJOIN_PREDS NUMBER
NONEQUIJOIN_PREDS NUMBER
RANGE_PREDS NUMBER
LIKE_PREDS NUMBER
NULL_PREDS NUMBER
TIMESTAMP DATE
313
314. SQL> create table T ( 5 special
2 skew varchar2(10),
3 even number); values
Table created.
SQL> insert into T
2 select
3 case
4 when rownum > 99995 then 'SPECIAL'
5 else dbms_random.string('U',8)
6 end,
7 mod(rownum,200)
8 from dual
9 connect by level <= 100000 even
10 /
distribution
100000 rows created.
314
315. SQL> exec dbms_stats.gather_table_stats(
user,'T', estimate_percent=>null);
PL/SQL procedure successfully completed.
SQL> select COLUMN_NAME,NUM_DISTINCT,DENSITY,
2 ( select count(*)
3 from user_tab_histograms
4 where table_name = 'T'
5 and column_name = c.column_name ) hist_cnt
6 from user_tab_cols c
7 where table_name = 'T'
8 order by table_name,COLUMN_ID
9 /
COLUMN_NAME NUM_DISTINCT DENSITY HIST_CNT
------------------- ------------ ---------- ----------
SKEW 99996 .00001 2
EVEN 200 .005 2
315
316. SQL> select * from T where skew = 'SPECIAL';
SKEW VAL
---------- ----------
SPECIAL 196
SPECIAL 197
SPECIAL 198
SPECIAL 199
SPECIAL 0
5 rows selected.
SQL> select * from T where even = 5;
TAG VAL
---------- ----------
IBRXGVIE 5
[snip]
500 rows selected.
316
317. SQL> exec dbms_stats.gather_table_stats(
user,'T', estimate_percent=>null);
PL/SQL procedure successfully completed.
SQL> select COLUMN_NAME,NUM_DISTINCT,DENSITY,
2 ( select count(*)
3 from user_tab_histograms
4 where table_name = 'T'
5 and column_name = c.column_name ) hist_cnt
6 from user_tab_cols c
7 where table_name = 'T'
8 order by table_name,COLUMN_ID
9 /
COLUMN_NAME NUM_DISTINCT DENSITY HIST_CNT
------------------- ------------ ---------- ----------
SKEW 99996 .00001 2
EVEN 200 .000005 200
317
324. SQL> desc CONFERENCE_ATTENDEES
Name Null? Type
----------------------------- -------- --------------
PID NUMBER
GENDER CHAR(1)
NAME VARCHAR2(40)
AGE NUMBER
DEATH_RATE NUMBER
324
335. SQL> desc INDEX_STATS
Name Null? Type
----------------------------- -------- --------------
HEIGHT NUMBER
BLOCKS NUMBER
NAME VARCHAR2(30)
PARTITION_NAME VARCHAR2(30)
...
OPT_CMPR_COUNT NUMBER
OPT_CMPR_PCTSAVE NUMBER
335
