SQL Tuning 101 - Sep 2013

Connor McDonald
OracleDBA
co.uk
1
@connor_mc_d
connormcdonald.wordpress.com

11
Dump of memory from 0x07246400 to 0x07248400
1064B4C00 06A20000 08C0000A 0A07C47E 00020506 [...........~....]
1064B4C10 34BC0000 01000000 00030CBF 0A07C47C [4..............|]
1064B4C20 0002EC28 00020300 00000000 0004001D [...(............]
...
1064B6BF0 C10B02C1 0B06436F 6E6E6F72 C47E0605 [......Connor.~..]
table or index
block size
database version created in
relative block address

21
"last transaction for all accounts"

26
SQL> desc ACCOUNT
Name Null? Type
----------------------------------- -------- ------------------------
ACCOUNT_NUM NOT NULL NUMBER(8)
CURRENT_BALANCE NOT NULL NUMBER(14,2)
...
SQL> desc TRANSACTIONS
Name Null? Type
----------------------------------- -------- -------------------
TXN_SEQ NOT NULL NUMBER(11)
TXN_TS NOT NULL TIMESTAMP(6)
TXN_TYPE NOT NULL VARCHAR2(10)
AMOUNT NOT NULL NUMBER(11,2)

28
SQL> select ACCOUNT_NUM, max(TXN_TS) LAST_TS
2 from TRANSACTIONS, ACCOUNT
3 where <joins etc>
4 group by ACCOUNT_NUM
5 order by 1;

29
2 from TRANSACTIONS
4 order by 1;
simplified

30
2 from TRANSACTIONS t
4 order by 1;
--------------------------------------------------
| Id | Operation | Name |
--------------------------------------------------
| 0 | SELECT STATEMENT | |
| 1 | TABLE ACCESS FULL | TRANSACTIONS |
--------------------------------------------------

32
SQL> select /*+ PARALLEL(t 16) */
2 ACCOUNT_NUM, max(TXN_TS) LAST_TS
5 order by 1;

36
create index TRANSACTIONS_IX on TRANSACTIONS (
account_num, txn_ts )
4 order by 1;
--------------------------------------------------
| Id | Operation | Name |
--------------------------------------------------
| 0 | SELECT STATEMENT | |
| 1 | INDEX FAST FULL SCAN| TRANSACTIONS_IX |
--------------------------------------------------

40
CREATE TABLE TRANSACTIONS
(
...
)
PARTITION BY RANGE (TXN_TS)
INTERVAL( NUMTOYMINTERVAL(1,'MONTH'))
(
PARTITION P1 VALUES LESS THAN (TIMESTAMP' 2009-01-01 00:00:00')
PARTITION P2 VALUES LESS THAN (TIMESTAMP' 2009-06-01 00:00:00')
...
);

41
3 where TXN_TS > add_months(sysdate,-12)
5 order by 1;

42
---------------------------------------------------------------
| Id | Operation | Name |Pstart| Pstop |
--------------------------------------------------------------
| 0 | SELECT STATEMENT | | | |
| 1 | PARTITION RANGE ITER..| | 127 | 138 |
|* 2 | TABLE ACCESS FULL | TRANSACTIONS | 127 | 138 |
-------------------------------------------------------------

49
SQL> insert into GTT_LAST_TXN
2 select ACCOUNT_NUM, max(TXN_TS) LAST_TS
4 where TXN_TS >= trunc(sysdate,'MM')
5 group by ACCOUNT_NUM;
for i in (
select ACCOUNT_NUM from ACCOUNTS
minus
select ACCOUNT_NUM from GTT_LAST_TXN
)
insert into GTT_LAST_TXN
select /*+ INDEX_DESC(t (account_num, txn_ts)) */ MAX(TXN_TS)
from TRANSACTIONS t
where ACCOUNT_NUM = i.ACCOUNT_NUM
and TXN_TS < trunc(sysdate,'MM')

53
SQL> select ...
2 from ...
3 where ...

55
"we have an interest in recent
activity for account holders"
"last transaction for all accounts"

promotional material
56
"we haven't seen you in a while,
here's a discount on ...."

60
SQL> desc ACCOUNT
Name Null? Type
----------------------------------- -------- ---------------
...
...
...
MODIFICATION_TS NOT NULL TIMESTAMP(6)

62
select ..., MODIFICATION_TS
into ..., :prev_modtstamp
from ACCOUNT
where ...
update ACCOUNT
set ...
where ACCOUNT_NUM = :b1
and MODIFICATION_TS = :prev_modtstamp
if SQL%NOTFOUND then
msg('Row has been changed by another user, please requery');
end if;

63
SQL> select ACCOUNT_NUM,
2 MODIFICATION_TS approx_last_usage
3 from ACCOUNT

66
SQL> desc ACCOUNT
Name Null? Type
------------------------------- -------- --------------
...

67
update ACCOUNT
set ...
where ACCOUNT_NUM = :b1
and MODIFICATION_TS = :prev_modtstamp
LAST_TXN_TS = systimestamp
LARGEST_TXN_AMT = greatest(TXN_AMT,LARGEST_TXN_AMT)
BALANCE_CEILING = greatest(BALANCE,BALANCE_CEILING)
BALANCE_FLOOR = least(BALANCE,BALANCE_FLOOR)

68
SQL> desc ACCOUNT
Name Null? Type
----------------------------------- -------- ---------------
LAST_WITHDRAWAL_TS TIMESTAMP(6)
LAST_DEPOSIT_TS TIMESTAMP(6)
LAST_TXN_TS TIMESTAMP(6)
LARGEST_TXN_AMT NUMBER(14,2)
BALANCE_CEILING NUMBER(14,2)
BALANCE_FLOOR NUMBER(14,2)

(semi) automate
70
"we haven't seen you in a while,
here's a discount on ...."

all solutions shown ...
84
denormalised
indexes
structure
horse power

104
constipation
dizziness
drowsiness
headache
lightheadedness
nausea
mood swingssweating
vomitingrash
itching
difficulty breathing
tightness in the chest
swelling of the mouth
confusion
disorientation
fainting
irregular heartbeat
hallucinations
seizures
sudden chest pain
unusual bruising or bleeding
blurred vision

"This is not a complete list"
105

triage
106
find the (likely) pain
stop the bleeding
avoid side effects
work toward cure

where not too look ...
109
(maybe)

"server CPU is 45%"
111
"buffer cache is 99%"

"no problems last 15 minutes"
114

125
procedure MY_PROC(...) is
begin
dbms_application_info.set_module('MY_PROC');
dai.set_client_info(' p_parm1 = '||p_parm1);
dai.set_client_info(' p_parm2 = '||p_parm2);
select ...
update ...
dai.set_action('now loading changes');
...
end;

131
SQL> desc V$ACTIVE_SESSION_HISTORY
Name Null? Type
------------------------------- -------- -------------------
SAMPLE_ID NUMBER
SAMPLE_TIME TIMESTAMP(3)
IS_AWR_SAMPLE VARCHAR2(1)
SESSION_ID NUMBER
SESSION_SERIAL# NUMBER
SESSION_TYPE VARCHAR2(10)
FLAGS NUMBER
USER_ID NUMBER
SQL_ID VARCHAR2(13)
IS_SQLID_CURRENT VARCHAR2(1)
SQL_CHILD_NUMBER NUMBER
SQL_OPCODE NUMBER
SQL_OPNAME VARCHAR2(64)
FORCE_MATCHING_SIGNATURE NUMBER
TOP_LEVEL_SQL_ID VARCHAR2(13)
TOP_LEVEL_SQL_OPCODE NUMBER
SQL_PLAN_HASH_VALUE NUMBER
SQL_PLAN_LINE_ID NUMBER
SQL_PLAN_OPERATION VARCHAR2(30)

"This morning, my screen froze
for 3 mins running Pay Adjustment..."
132

133
SQL> select sql_id,
2 sql_exec_id,
3 count(*)
4 from v$active_session_history
5 where program = 'Finance.exe'
6 and module = 'PayAdjust'
7 and sample_time >
timestamp '2013-08-20 08:00:00'
8 and sql_id is not null
9 group by
10 sql_id,
11 sql_exec_id
12 order by 3 desc ;

134
SQL_ID SQL_EXEC_ID COUNT(*)
------------- ----------- ----------
087jnbt3bg3fn 33562711 178
9n2nx15wj6tb3 33512732 39
7nvh5pd4y5nqu 33562791 36
7nvh5pd4y5nqu 33562735 30
7nvh5pd4y5nqu 33562736 29
6b5r2j5p2z7kk 33671666 14
6b5r2j5p2z7kk 33670545 12
7nvh5pd4y5nqu 33562689 11
bamffwpy8v8bt 33554432 9
...

135
# cd $ORACLE_HOME/rdbms/admin
# sqlplus / as sysdba @ashrpt

138
SQL> select sql_fulltext
2 from v$sql
3 where sql_id = '087jnbt3bg3fn';
SQL_FULLTEXT
-----------------------------------------------
SELECT ...
FROM ...

146
serialised access
aka, someone waits

SGA
protected by
2) access memory

SGA
protected by
3) release latch

154
SQL> select sql_fulltext
2 from v$sqlstats
3 where sql_id = '087jnbt3bg3fn';
SQL_FULLTEXT
-----------------------------------------------
SELECT ...
FROM ...

"The column definitions for columns in V$SQLSTATS are
identical to those in the V$SQL and V$SQLAREA views.
However, the V$SQLSTATS view differs from V$SQL and
V$SQLAREA in that it is faster, more scalable, and has a
greater data retention (the statistics may still appear in
this view, even after the cursor has been aged out of the
shared pool)."
155

SQL> select e.department_id, sum(salary)
2 from emp e,
3 job_hist j
4 where e.employee_id = j.employee_id
5 and extract(year from e.hire_date) > 1985
6 and j.end_date > j.start_date + 1
7 and j.start_date >= e.hire_date
8 group by e.department_id
157

... it cannot run better
161
legitimate response

be like the optimizer
162
only smarter

167
SQL> alter session set events =
2 '10053 trace name context forever, level 1';
Session altered.
SQL> explain plan for
2 select e.empno, d.dname
3 from emp e,
4 dept d
5 where e.deptno = d.deptno
6 and e.ename like '%A%'
7 and d.deptno != 5;
Explained.

168
SQL> select p.tracefile
2 from v$session s, v$process p
3 where s.paddr = p.addr
4 and s.sid = sys_context('USERENV','SID');
TRACEFILE
----------------------------------------------
/u01/app/oracle/diag/..../MYDB_ora_2994270.trc

169
---------------------
QUERY BLOCK SIGNATURE
---------------------
signature (): qb_name=SEL$1 nbfros=2 flg=0
fro(0): flg=4 objn=51562 hint_alias="D"@"SEL$1"
fro(1): flg=4 objn=51564 hint_alias="E"@"SEL$1"
******************************************
----- Current SQL Statement (sql_id=gvg2yvpdr4uaw) -----
explain plan for
select e.empno, d.dname
from emp e,
dept d
where e.deptno = d.deptno
and e.ename like '%A%'
and d.deptno != 5
*******************************************

170
******************************
PARAMETERS
******************************
Compilation Environment Dump
optimizer_mode_hinted = false
optimizer_features_hinted = 0.0.0
parallel_execution_enabled = true
parallel_query_forced_dop = 0
parallel_dml_forced_dop = 0
parallel_ddl_forced_degree = 0
parallel_ddl_forced_instances = 0
_query_rewrite_fudge = 90
optimizer_features_enable = 11.2.0.2
_optimizer_search_limit = 5

171
Considering Query Transformations
**************************
*************************
Common Subexpression elimination
Order-by elimination
Join Elimination
*************************
SQL:******* UNPARSED QUERY IS *******
SELECT "E"."EMPNO" "EMPNO","D"."DNAME" "DNAME"
FROM "SCOTT"."EMP" "E","SCOTT"."DEPT" "D"
WHERE "E"."DEPTNO"="D"."DEPTNO"
AND "E"."ENAME" LIKE '%A%'
AND "D"."DEPTNO"<>5

172
Predicate Move-Around (PM)
**************************
"E"."DEPTNO"="D"."DEPTNO" AND
"E"."ENAME" LIKE '%A%'
AND "D"."DEPTNO"<>5
...
finally:
"E"."DEPTNO"="D"."DEPTNO" AND
"E"."ENAME" LIKE '%A%' AND
"D"."DEPTNO"<>5 AND
"E"."DEPTNO"<>5

173
SINGLE TABLE ACCESS PATH
Single Table Cardinality Estimation for EMP[E]
Table: EMP Alias: E
Card: Original: 14.000000 Rounded: 1 Computed: 0.70
Access Path: TableScan
Cost: 4.00 Resp: 4.00 Degree: 0
Cost_io: 4.00 Cost_cpu: 41081
Resp_io: 4.00 Resp_cpu: 41081
Best:: AccessPath: TableScan
Cost: 4.00 Degree: 1 Resp: 4.00 Card: 0.70 Bytes: 0

174
Access path analysis for DEPT
***************************************
Single Table Cardinality Estimation for DEPT[D]
Using prorated density: 0.208333 of col #1 as
selectvity of out-of-range/non-existent value pred
Table: DEPT Alias: D
Card: Original: 4.000000 Rounded: 3 Computed: 3.17
Cost: 4.00 Resp: 4.00 Degree: 0
Cost_io: 4.00 Cost_cpu: 36467
Resp_io: 4.00 Resp_cpu: 36467
Best:: AccessPath: TableScan

175
Join order[1]: EMP[E]#0 DEPT[D]#1
***************
Now joining: DEPT[D]#1
***************
NL Join
Outer table: Card: 0.70 Cost: 4.00 Resp: 4.00 Degree: 1
Bytes: 13
Access path analysis for DEPT
Access Path: index (UniqueScan)
Index: PK_DEPT

176
SM Join
SM cost: 10.01
Outer table: EMP Alias: E
resc: 4.00 card 0.70 bytes: 13 deg: 1 resp: 4.00
Inner table: DEPT Alias: D
resc: 4.00 card: 3.17 bytes: 13 deg: 1 resp: 4.00
HA Join
HA cost: 8.51
resc: 8.51 resc_io: 8.00 resc_cpu: 4367998
resp: 8.51 resp_io: 8.00 resp_cpu: 4367998
Best:: JoinMethod: NestedLoop

177
Join order[2]: DEPT[D]#1 EMP[E]#0
***************
Now joining: EMP[E]#0
***************
NL Join
...
SM Join
...
HA Join
...

178
------------------------------------------------+---------------+
| Id | Operation | Name | Rows | Cost |
------------------------------------------------+----------------
| 0 | SELECT STATEMENT | | | 5 |
| 1 | NESTED LOOPS | | | |
| 2 | NESTED LOOPS | | 1 | 5 |
| 3 | TABLE ACCESS FULL | EMP | 1 | 4 |
| 4 | INDEX UNIQUE SCAN | PK_DEPT | 1 | 0 |
| 5 | TABLE ACCESS BY INDEX ROWID | DEPT | 1 | 1 |
------------------------------------------------+---------------+

can I write it better ?
180
CONSIDERING QUERY TRANSFORMATIONS

where should I start ?
181

what should I join to (next) ?
182
Join order[1]: EMP[E]#0 DEPT[D]#1

how should I join ?
183
NL Join
HA Join
SM Join

186
SQL> set autotrace traceonly stat
SQL> select * from STUFF
2 where CREATED > sysdate
Statistics
------------------------------------------
651 recursive calls
0 db block gets
2243 consistent gets
24 physical reads

188
SQL> variable c clob
SQL> begin
2 dbms_utility.expand_sql_text
3 ( 'select * from STUFF '||
4 'where created > sysdate',:c);
5 end;
6 /
PL/SQL procedure successfully completed.
SQL> print c

189
SQL> create or replace
2 view STUFF as
3 select
4 o.owner,
5 o.created,
6 s.bytes,
7 s.tablespace_name
8 from
9 dba_segments s,
10 all_objects o
11 where o.owner = s.owner
12 and o.object_name = s.segment_name;
View created.

190
SELECT "A1"."OWNER" "OWNER",
"A1"."NAME" "NAME",
"A1"."CREATED" "CREATED",
"A1"."BYTES" "BYTES",
"A1"."TABLESPACE_NAME" "TABLESPACE_NAME"
FROM (SELECT "A2"."OWNER" "OWNER",
"A2"."OBJECT_NAME" "NAME",
"A2"."CREATED" "CREATED",
"A3"."BYTES" "BYTES",
"A3"."TABLESPACE_NAME" "TABLESPACE_NAME" FROM (SELECT "A4"
."OWNER" "OWNER",
"A4"."SEGMENT_NAME" "SEGMENT_NAME",
"A4"."PARTITION_NAME" "PARTITION_NAME",
"A4"."SEGMENT_TYPE" "SEGMENT_TYPE",
"A4"."SEGMENT_SUBTYPE" "SEGMENT_SUBTYPE",
"A4"."TABLESPACE_NAME" "TABLESPACE_NAME",
"A4"."HEADER_FILE" "HEADER_FILE",
"A4"."HEADER_BLOCK" "HEADER_BLOCK",
DECODE(BITAND("A4"."SEGMENT_FLAGS",131072),131072,
"A4"."BLOCKS",DECODE(BITAND("A4"."SEGMENT_FLAGS",1),1,
"SYS"."DBMS_SPACE_ADMIN"."SEGMENT_NUMBER_BLOCKS"("A4"."TABLESPACE_ID",
"A4"."RELATIVE_FNO",
"A4"."HEADER_BLOCK",
"A4"."SEGMENT_TYPE_ID",
"A4"."BUFFER_POOL_ID",
"A4"."SEGMENT_FLAGS",
"A4"."SEGMENT_OBJD",
"A4"."BLOCKS"),
"A4"."BLOCKS"))*"A4"."BLOCKSIZE" "BYTES",
DECODE(BITAND("A4"."SEGMENT_FLAGS",131072),131072,
"A4"."BLOCKS",DECODE(BITAND("A4"."SEGMENT_FLAGS",1),1,
"SYS"."DBMS_SPACE_ADMIN"."SEGMENT_NUMBER_BLOCKS"("A4"."TABLESPACE_ID",

191
"A4"."BLOCKS"),
"A4"."BLOCKS")) "BLOCKS",DECODE(BITAND("A4"."SEGMENT_FLAGS",131072),131072,
"A4"."EXTENTS",DECODE(BITAND("A4"."SEGMENT_FLAGS",1),1,
"SYS"."DBMS_SPACE_ADMIN"."SEGMENT_NUMBER_EXTENTS"("A4"."TABLESPACE_ID",
"A4"."EXTENTS"),
"A4"."EXTENTS")) "EXTENTS",
"A4"."INITIAL_EXTENT" "INITIAL_EXTENT",
"A4"."NEXT_EXTENT" "NEXT_EXTENT",
"A4"."MIN_EXTENTS" "MIN_EXTENTS",
"A4"."MAX_EXTENTS" "MAX_EXTENTS",
"A4"."MAX_SIZE" "MAX_SIZE",
"A4"."RETENTION" "RETENTION",
"A4"."MINRETENTION" "MINRETENTION",
"A4"."PCT_INCREASE" "PCT_INCREASE",
"A4"."FREELISTS" "FREELISTS",
"A4"."FREELIST_GROUPS" "FREELIST_GROUPS",
"A4"."RELATIVE_FNO" "RELATIVE_FNO",
DECODE("A4"."BUFFER_POOL_ID",1,'KEEP',2,'RECYCLE','DEFAULT') "BUFFER_POOL",
DECODE("A4"."FLASH_CACHE",1,'KEEP',2,
'NONE','DEFAULT') "FLASH_CACHE",DECODE("A4"."CELL_FLASH_CACHE",1,'KEEP',2,'NONE','DEFAULT')
"CELL_FLASH_CACHE"
FROM ( (SELECT NVL("A199"."NAME",'SYS') "OWNER",
"A198"."NAME" "SEGMENT_NAME",

192
"A198"."SUBNAME" "PARTITION_NAME",
"A196"."OBJECT_TYPE" "SEGMENT_TYPE",
"A195"."TYPE#" "SEGMENT_TYPE_ID",DECODE(BIT
AND("A195"."SPARE1",2097408),2097152,'SECUREFILE',256,'ASSM','MSSM') "SEGMENT_SUBTYPE",
"A197"."TS#" "TABLESPACE_ID",
"A197"."NAME" "TABLESPACE_NAME",
"A197"."BLOCKSIZE" "BLOCKSIZE",
"A194"."FILE#" "HEADER_FILE",
"A195"."BLOCK#" "HEADER_BLOCK",
"A195"."BLOCKS"*"A197"."BLOCKSIZE" "BYTES",
"A195"."BLOCKS" "BLOCKS",
"A195"."EXTENTS" "EXTENTS",
"A195"."INIEXTS"*"A197"."BLOCKSIZE" "INITIAL_EXTENT",
"A195"."EXTSIZE"*"A197"."BLOCKSIZE" "NEXT_EXTENT",
"A195"."MINEXTS" "MIN_EXTENTS",
"A195"."MAXEXTS" "MAX_EXTENTS",DECODE(BITAND("A195"."SPARE1",4194304),4194304,
"A195"."BITMAPRANGES",NULL) "MAX_SIZE",TO_CHAR(DECODE(
BITAND("A195"."SPARE1",2097152),2097152,
DECODE("A195"."LISTS",0,'NONE',1,'AUTO',2,'MIN',3,'MAX',4,'DEFAULT','INVALID'),NULL))
"RETENTION",DECODE(BITAND("A195"."SPARE1",2097152),2097152,
"A195"."GROUPS",NULL) "MINRETENTION",DECODE(BITAND("A197"."FLAGS",3),1,TO_NUMBER(NULL),
"A195"."EXTPCT") "PCT_INCREASE",DECODE(BITAND("A197"."FLAGS",32),32,
TO_NUMBER(NULL),DECODE("A195"."LISTS",0,1,
"A195"."LISTS"))
"FREELISTS",DECODE(BITAND("A197"."FLAGS",32),32,TO_NUMBER(NULL),DECODE("A195"."GROUPS",0,1,
"A195"."GROUPS")) "FREELIST_GROUPS",
"A195"."FILE#" "RELATIVE_FNO",BITAND("A195"."CACHEHINT",3) "BUFFER_POOL_ID",
BITAND("A195"."CACHEHINT",12)/4 "FLASH_CACHE",BITAND("A195"."CACHEHINT",48)/16 "CELL_FLASH_CACHE",
NVL("A195"."SPARE1",0)
"SEGMENT_FLAGS",DECODE(BITAND("A195"."SPARE1",1),1,
"A195"."HWMINCR",
"A198"."DATAOBJ#") "SEGMENT_OBJD" FROM "SYS"."USER$" "A199",
"SYS"."OBJ$" "A198",
"SYS"."TS$" "A197", ( (SELECT

193
DECODE(BITAND("A209"."PROPERTY",8192),8192,'NESTED TABLE','TABLE') "OBJECT_TYPE",
2 "OBJECT_TYPE_ID",5 "SEGMENT_TYPE_ID",
"A209"."OBJ#" "OBJECT_ID",
"A209"."TS#" "TS_NUMBER" FROM "SYS"."TAB$" "A209" WHERE BITAND("A209"."PROPERTY",1024)=0) UNI
ON ALL (SELECT 'TABLE PARTITION' "OBJECT_TYPE",19 "OBJECT_TYPE_ID",5 "SEGMENT_TYPE_ID",
"A208"."TS#" "TS_NUMBER" FROM "SYS"."TABPART$" "A208") UNION ALL
(SELECT 'CLUSTER' "OBJECT_TYPE",3 "OBJECT_TYPE_ID",5 "SEGMENT_TYPE_ID",
"A207"."TS#" "TS_NUMBER" FROM "SYS"."CLU$" "A207") UNION ALL
(SELECT DECODE("A206"."TYPE#",8,'LOBINDEX','INDEX') "OBJECT_TYPE",1 "OBJECT_TYPE_ID",6
"SEGMENT_TYPE_ID",
"A206"."TS#" "TS_NUMBER" FROM "SYS"."IND$" "A206" WHERE "A206"."TYPE#"=1 OR
"A206"."TYPE#"=2 OR
"A206"."TYPE#"=3 OR
"A206"."TYPE#"=4 OR
"A206"."TYPE#"=6 OR
"A206"."TYPE#"=7 OR
"A206"."TYPE#"=8 OR
"A206"."TYPE#"=9) UNION ALL
(SELECT 'INDEX PARTITION'
"OBJECT_TYPE",20 "OBJECT_TYPE_ID",6 "SEGMENT_TYPE_ID",

194
"A205"."TS#" "TS_NUMBER" FROM "SYS"."INDPART$" "A205") UNION ALL
(SELECT 'LOBSEGMENT' "OBJECT_TYPE",21 "OBJECT_TYPE_ID",8 "SEGMENT_TYPE_ID",
"A204"."LOBJ#" "OBJECT_ID",
"A204"."TS#" "TS_NUMBER" FROM "SYS"."LOB$" "A204" WHERE BITAND("A204"."PROPERTY",64)=0 OR
BITAND("A204"."PROPERTY",128)=128) UNION ALL
(SELECT 'TABLE SUBPARTITION' "OBJECT_TYPE",34 "OBJECT_TYPE_ID",5 "SEGMENT_TYPE_ID",
"A203"."TS#" "TS_NUMBER" FROM "SYS"."TABSUBPART$" "A203") UNION ALL
(SELECT 'INDEX SUBPARTITION' "OBJECT_TYPE",35 "OBJECT_TYPE_ID",6 "SEGMENT_TYPE_ID",
"A202"."TS#" "TS_NUMBER" FROM "SYS"."INDSUBPART$" "A202") UNION ALL
(SELECT DECODE("A201"."FRAGTYPE$",'P','LOB PARTITION','LOB SUBPARTITION')
"OBJECT_TYPE",DECODE("A201"."FRAGTYPE$",'P',40,41) "OBJECT_TYPE_ID",8 "SEGMENT_TYPE_ID",
"A201"."FRAGOBJ#" "OBJECT_ID",
"A201"."TS#" "TS_NUMBER" FROM "SYS"."LOBFRAG$" "A201")) "A196",
"SYS"."SEG$" "A195",
"SYS"."FILE$" "A194" WHERE "A195"."FILE#"="A196"."HEADER_FILE" AND
"A195"."BLOCK#"="A196"."HEADER_BLOCK" AND
"A195"."TS#"="A196"."TS_NUMBER" AND
"A195"."TS#"="A197"."TS#" AND
"A198"."OBJ#"="A196"."OBJECT_ID" AND
"A198"."OWNER#"="A199"."USER#"(+) AND
"A195"."TYPE#"="A196"."SEGMENT_TYPE_ID" AND
"A198"."TYPE#"="A196"."OBJECT_TYPE_ID" AND
"A195"."TS#"="A194"."TS#" AND

195
"A195"."FILE#"="A194"."RELFILE#") UNION ALL
(SELECT NVL("A193"."NAME",'SYS') "OWNER",
"A191"."NAME" "SEGMENT_NAME",NULL "PARTITION_NAME",
DECODE("A190"."TYPE#",1,'ROLLBACK',10,'TYPE2 UNDO') "SEGMENT_TYPE",
"A190"."TYPE#" "SEGMENT_TYPE_ID",NULL "SEGMENT_SUBTYPE",
"A190"."BITMAPRANGES",NULL) "MAX_SIZE",NULL "RETENTION",NULL "MINRETENTION",
"A190"."EXTPCT"
"PCT_INCREASE",DECODE(BITAND("A192"."FLAGS",32),32,TO_NUMBER(NULL),DECODE("A190"."LISTS",0,1,
"A190"."LISTS")) "FREELISTS",DECODE(BITAND("A192"."FLAGS",32),32,TO_NUMBER(NULL),
DECODE("A190"."GROUPS",0,1,"A190"."GROUPS")) "FREELIST_GROUPS",
"A190"."FILE#" "RELATIVE_FNO",BITAND("A190"."CACHEHINT",3)
"BUFFER_POOL_ID",BITAND("A190"."CACHEHINT",12)/4 "FLASH_CACHE",
BITAND("A190"."CACHEHINT",48)/16 "CELL_FLASH_CACHE",NVL("A190"."SPARE1",0) "SEGMENT_FLAGS",
"A191"."US#" "SEGMENT_OBJD" FROM "SYS"."USER$" "A193","SYS"."TS$" "A192",
"SYS"."UNDO$" "A191",
"SYS"."SEG$" "A190",
"SYS"."FILE$" "A189" WHERE "A190"."FILE#"="A191"."FILE#" AND
"A190"."BLOCK#"="A191"."BLOCK#" AND
"A190"."TS#"="A191"."TS#" AND
"A190"."TS#"="A192"."TS#" AND
"A190"."USER#"="A193"."USER#"(+) AND
("A190"."TYPE#"=1 OR
"A190"."TYPE#"=10) AND
"A191"."STATUS$"<>1 AND

196
"A191"."TS#"="A189"."TS#" AND
(SELECT NVL("A188"."NAME",'SYS') "OWNER",
TO_CHAR("A185"."FILE#")||'.'||TO_CHAR("A186"."BLOCK#") "SEGMENT_NAME",NULL "PARTITION_NAME",
DECODE("A186"."TYPE#",2,'DEFERRED ROLLBACK',3,
'TEMPORARY',4,'CACHE',9,'SPACE HEADER','UNDEFINED') "SEGMENT_TYPE",
"A186"."BITMAPRANGES",NULL) "MAX_SIZE",NULL
"RETENTION",NULL "MINRETENTION",DECODE(BITAND("A187"."FLAGS",3),1,TO_NUMBER(NULL),
"A186"."EXTPCT")
"PCT_INCREASE",DECODE(BITAND("A187"."FLAGS",32),32,TO_NUMBER(NULL),DECODE("A186"."LISTS",0,1,
"A186"."LISTS"))
"A186"."FILE#" "RELATIVE_FNO",BITAND("A186"."CACHEHINT",3)
"BUFFER_POOL_ID",BITAND("A186"."CACHEHINT",12)/4 "FLASH_CACHE",BITAND("A186"."CACHEHINT",48)/16
"CELL_FLASH_CACHE",NVL("A186"."SPARE1",0) "SEGMENT_FLAGS",
"A186"."HWMINCR" "SEGMENT_OBJD" FROM "SYS"."USER$"
"A188",
"SYS"."TS$" "A187",
"SYS"."SEG$" "A186",
"SYS"."FILE$" "A185" WHERE "A186"."TS#"="A187"."TS#" AND
"A186"."USER#"="A188"."USER#"(+) AND
"A186"."TYPE#"<>1 AND
"A186"."TYPE#"<>5 AND

197
"A186"."TYPE#"<>6 AND
"A186"."TYPE#"<>8 AND
"A186"."TYPE#"<>10 AND
"A186"."TYPE#"<>11 AND
"A186"."TS#"="A185"."TS#"
AND
(SELECT NVL("A184"."NAME",'SYS') "OWNER",'HEATMAP' "SEGMENT_NAME",
NULL "PARTITION_NAME",'SYSTEM STATISTICS' "SEGMENT_TYPE",
"A183"."BLO
CKSIZE" "BLOCKSIZE",
"A182"."BITMAPRANGES",NULL) "MAX_SIZE",NULL "RETENTION",NULL
"MINRETENTION",DECODE(BITAND("A183"."FLAGS",3),1,TO_NUMBER(NULL),
"A182"."EXTPCT") "PCT_INCREASE",DECODE(BITAND("A183"."FLAGS",32),32,TO_NUMBER(NULL),DEC
ODE("A182"."LISTS",0,1,
"A182"."LISTS"))
"A182"."FILE#" "RELATIVE_FNO",BITAND("A182"."CACHEHINT",3) "BUFFER_POOL_ID",
BITAND("A182"."CACHEHINT",12)/4 "FLASH_CACHE",BITAND("A18
2"."CACHEHINT",48)/16 "CELL_FLASH_CACHE",NVL("A182"."SPARE1",0) "SEGMENT_FLAGS",
"A182"."HWMINCR" "SEGMENT_OBJD" FROM "SYS"."USER$" "A184",

198
"SYS"."TS$" "A183",
"SYS"."SEG$" "A182",
"SYS"."FILE$" "A181" WHERE "A182"."TS#"="A183"."TS#" AND
"A182"."USER#"="A184"."USER#"(+) AND
"A182"."TYPE#"=11 AND
"A182"."TS#"="A181"."TS#" AND
"A182"."FILE#"="A181"."RELFILE#")) "A4") "A3", (SELECT "A5"."NAME" "OWNER",
"A6"."NAME" "OBJECT_NAME",
"A6"."SUBNAME" "SUBOBJECT_NAME",
"A6"."DATAOBJ#" "DATA_OBJECT_ID",DECODE("A6"."TYPE#",0,'NEXT OBJECT',1,'INDEX',
2,'TABLE',3,'CLUSTER',4,'VIEW',5,'SYNONYM
',6,'SEQUENCE',7,'PROCEDURE',8,'FUNCTION',9,'PACKAGE',11,'PACKAGE BODY',12,
'TRIGGER',13,'TYPE',14,'TYPE BODY',19,'TABLE PARTITION',20,'INDEX PARTITION',
21,'LOB',22,'LIBRARY',23,'DIRECTORY',24,'QUEUE',28,'JAVA SOURCE',29,'JAVA CLASS',30,
'JAVA RESOURCE',32,'INDEXTYPE',33,'OPERATOR',34,
'TABLE SUBPARTITION',35,'INDEX SUBPARTITION',40,'LOB PARTITION',41,'LOB SUBPARTITION',42
,NVL( (SELECT 'REWRITE EQUIVALENCE' "'REWRITEEQUIVALENCE'" FROM SYS."SUM$" "A52" WHERE "A52"."OBJ#"="A6"."OBJ#" AND
BITAND("A52"."XPFLAGS",8388608)=8388608),'MATERIALIZED VIEW'),43,'DIMENSION',
44,'CONTEXT',46,'RULE SET',47,'RESOURCE PLAN',48,'CONSUMER GROUP',55,'XML SCHEMA',56,'JAVA
DATA',57,'EDITION',59,'RULE',
60,'CAPTURE',61,'APPLY',62,'EVALUATION CONTEXT',66,'JOB',67,'PROGRAM',68,'JOB CLASS',69,
'WINDOW',72,'SCHEDULER GROUP',74,'SCHEDULE',79,'CHAIN',81,'FILE GROUP',82,'MINING
MODEL',87,'ASSEMBLY',90,'CREDENTIAL',92,'CUBE
DIMENSION',93,'CUBE',94,'MEASURE FOLDER',95,'CUBE BUILD PROCESS',100,'FILE WATCHER',
101,'DESTINATION',114,'SQL TRANSLATION PROFILE',115,'UNIFIED AUDIT POLICY','UNDEFINED') "OBJECT_TYPE",
"A6"."CTIME" "CREATED",
"A6"."MTIME" "LAST_DDL_TIME",TO_CHAR("A6"."STIME",'YYYY-MM-DD:HH24:MI:SS') "TIMESTAMP",DEC
ODE("A6"."STATUS",0,'N/A',1,'VALID','INVALID') "STATUS",DECODE(BITAND("A6"."FLAGS",2),0,'N',2,'Y','N')
"TEMPORARY",DECODE(BITAND("A6"."FLAGS",4),0,'N',4,'Y','N') "GENERATED",DECODE(BITAND("A6"."FLAGS",16),0,'N',16,'Y','N')
"SECONDARY",
"A6"."NAMESPACE" "NAMESPACE",
"A6"."DEFINING_EDITION" "EDITION_NAM
E",DECODE(BITAND("A6"."FLAGS",196608),65536,'METADATA LINK',131072,'OBJECT LINK','NONE') "SHARING",
CASE WHEN ("A6"."TYPE#"=4 OR
"A6"."TYPE#"=5 OR

203
SQL> select *
2 from STUDENT
3 where gender = 'W';

full scan
(dba_extents)
File 1, Block 271, 512 blocks
File 2, Block 234, 256 blocks
etc

indexed access
W, File 1, Block 37, Row 4
W, File 1, Block 437, Row 11
Sue
Jane
POOL_IX (POOL_TYPE) STUDENT

what will a full scan cost ?
206

207
SQL> select blocks
2 from dba_tables
3 where owner = 'SCOTT'
4 and table_name = 'STUDENT';
BLOCKS
----------
9083

209
SQL> select value
2 from v$parameter
3 where name = 'db_file_multiblock_read_count';
VALUE
---------------
128

IO cost blocks / blocks at a time
210

adj = 1.6765 x orig0.6581
212
Ack: Wolfgang Brietling, 2001

214
SQL> set autotrace traceonly explain
SQL> select /*+ no_cpu_costing */ * from STUDENT;
-----------------------------------------------------
-----------------------------------------------------
| 0 | SELECT STATEMENT | | 531K| 224 |
| 1 | TABLE ACCESS FULL| STUDENT | 531K| 224 |
-----------------------------------------------------
9083 / 41 = 221

215
SQL> select /*+ no_cpu_costing */ * from STUDENT;
-----------------------------------------------------
-----------------------------------------------------
-----------------------------------------------------
9083 / 41 = 221

218
SQL> select * from STUDENT;
-----------------------------------------------------
-----------------------------------------------------
-----------------------------------------------------

what will a index scan cost ?
219

221
SQL> select AVG_LEAF_BLOCKS_PER_KEY
2 from USER_INDEXES
3 where INDEX_NAME = 'STUDENT_IX'
AVG_LEAF_BLOCKS_PER_KEY
-----------------------
6

run a few...
valid use of hints

nested loops
hash
sort merge
index join
and-equal
btree-bitmap conversion
bitmap join

other complexities
bloom filters
parallel

"for each row in outer,
check for row in inner"

for (i=1; i<100; i++)
for (j=1; j<100; j++)
for (k=1; k<100; k++)
...
...

effort = L1 + M * L2
=
cost to Lookup rows
in outer table
number of rows Matching
criteria in outer table
cost of Lookup matching row
in inner table

High M ... no good
=

High L2 ... no good
=

High L1 ... no good maybe

effort = S1 + S2 + M
sort table 1 (hold result)
sort table 2 (hold result)
merge results (not held*)

RAM
SQL> select value * 0.05 / 1024 sort_kb
2 from v$parameter
3 where name = 'pga_aggregate_target';
SORT_KB
----------
2457.6

SQL> select * from v$mystat / v$sesstat / v$sysstat
2 where name like 'work%';
NAME VALUE
----------------------------------- ----------
workarea executions - optimal 12
workarea executions - onepass 0
workarea executions - multipass 0

non-equality joins
where t1.name > t2.name

260
SQL> select value
2 from v$parameter
3 where name = 'hash_join_enabled';
VALUE
----------------------
true

nested loop
good selectivity into each table
small numbers of (result) rows
first row fast
269

hash join
the "best" join (theory)
270

sort merge
rarely seen
partial joins
271

SQL> select e.department_id, sum(salary)
2 from emp e,
3 job_hist j
4 where e.employee_id = j.employee_id
5 and extract(year from e.hire_date) > 1985
6 and j.end_date > j.start_date + 1
7 and j.start_date >= e.hire_date
8 group by e.department_id
273

-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)|
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 36M| 2742M| | 10998 (48)|
| 1 | HASH GROUP BY | | 36M| 2742M| | 10998 (48)|
|* 2 | HASH JOIN | | 36M| 2742M| 3728K| 9137 (37)|
|* 3 | TABLE ACCESS FULL| JOB_HIST | 88761 | 2687K| | 147 (3)|
|* 4 | TABLE ACCESS FULL| EMP | 877K| 40M| | 3028 (2)|
-----------------------------------------------------------------------------
275

SQL> select
2 DBMS_SQLTUNE.REPORT_SQL_MONITOR(
3 sql_id=>'d3ncuxj7629bf',
4 report_level=>'ALL',
5 type=>'HTML') as report
6 from dual;
280

options
284
rewrite the sql
hints
add indexes
remove indexes

288
cardinality is everything
288

292
actual versus estimate
292

293
SQL> select /*+ GATHER_PLAN_STATISTICS */ count(*)
2 from VEHICLES
3 where MAKE = 'FORD'
4 and MODEL = 'FOCUS';
COUNT(*)
----------
214468
293

294
SQL> SELECT *
2 FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(
3 NULL, NULL, 'ALLSTATS LAST'));
-----------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows |
-----------------------------------------------------------------
| 1 | SORT AGGREGATE | | 1 | 1 | 1 |
|* 2 | TABLE ACCESS FULL| VEHICLES| 1 | 220K| 214K|
-----------------------------------------------------------------
294

295
295
if the estimate is wrong

297
SQL> create table TOUGH_DATA as
2 select
3 rownum pk,
4 dbms_random.string('U',10) str
5 from dual
6 connect by level < 1000000
7 /
Table created.
SQL> exec dbms_stats.gather_table_stats(
user,'TOUGH_DATA')

298
SQL> select count(*)
2 from TOUGH_DATA
3 where str like '%XX'
4 /
COUNT(*)
----------
1452
hard

299
SQL> select count(*)
2 from TOUGH_DATA
4 /
-------------------------------------------------
| Id | Operation | Name | Rows |
-------------------------------------------------
| 0 | SELECT STATEMENT | | 1 |
| 1 | SORT AGGREGATE | | 1 |
|* 2 | TABLE ACCESS FULL| TOUGH_DATA | 50000 |
-------------------------------------------------
5% assumption

300
SQL> select /*+ dynamic_sampling(t 2) */ count(*)
2 from TOUGH_DATA t
4 /
-------------------------------------------------
-------------------------------------------------
| 1 | SORT AGGREGATE | | 1 |
|* 2 | TABLE ACCESS FULL| TOUGH_DATA | 1252 |
-------------------------------------------------

303
"optimizer hints should only be
used with extreme care"
Maria Colgan, Oct 2012
Optimizer product manager

305
gather_plan_statistics
dynamic_sampling
monitor
qb_name

for (int i = 0; i < w.Count; ++i)
{
if (w[i].v > 0 && w[i].p > mddh)
{
m = Math.Max(m, w[i].d);
}
}
for (int i = 0; i < w.Count; ++i)
{
if (w[i].v > 0 && w[i].p > mddh)
{
w[i].d = m / w[i].d;
s += w[i].d;
}
}
311

query blocks =
self- documenting SQL
312

select emp.*
from emp,
( select trunc(hiredate,'YYYY'), max(empno) empno
from emp
where empno > 0
group by trunc(hiredate,'YYYY') ) x,
( select deptno, avg(sal)
from emp
group by deptno ) y
where x.empno = emp.empno
and y.deptno = emp.deptno
313

Id | Operation | Name |
----------------------------------------------|
0 | SELECT STATEMENT | |
1 | HASH JOIN | |
2 | TABLE ACCESS BY INDEX ROWID | EMP |
3 | NESTED LOOPS | |
4 | VIEW | |
5 | SORT GROUP BY | |
6 | TABLE ACCESS BY INDEX ROWID| EMP |
7 | INDEX FULL SCAN | E2 |
8 | INDEX RANGE SCAN | E1 |
9 | VIEW | |
314

select emp.*
from emp,
( select /*+ QB_NAME(YR_HIRE) */
trunc(hiredate,'YYYY'), max(empno) empno
from emp
where empno > 0
( select /*+ QB_NAME(AV_SAL) */
deptno, avg(sal)
from emp
group by deptno ) y
315

Id | Operation | Name | Query Block
----------------------------------------------|--------------
0 | SELECT STATEMENT | |
1 | HASH JOIN | |
3 | NESTED LOOPS | |
4 | VIEW | |
6 | TABLE ACCESS BY INDEX ROWID| EMP |
7 | INDEX FULL SCAN | E2 |
9 | VIEW | |
SEL$1
SEL$1
AV_SAL
AV_SAL
AV_SAL
AV_SAL
SEL$1
YR_HIRE
YR_HIRE
YR_HIRE
YR_HIRE
316

select
/*+ QB_NAME(top)
INDEX(@yr_hire emp (empno))
FULL(@av_sal emp) */
emp.*
from emp,
( select /*+ QB_NAME(YR_HIRE) */
trunc(hiredate,'YYYY'), max(empno) empno
from emp
where empno > 0
( select /*+ QB_NAME(AV_SAL) */
deptno, avg(sal)
from emp
group by deptno ) y
318

320
select
/*+ QB_NAME(top)
INDEX(@yr_hire emp (empno))
FULL(@av_sal emp)
*/
INDEX(emp emp_ix)

322
first_rows_n
all_rows
leading
cardinality
statement_queueing
opt_param

326
full
index
use_hash
use_nl
etc

332
SQL> select /*+ INDEX(accounts_pk) */
2 from ACCOUNTS
3 where ...
SQL> select /*+ INDEX(a) */
2 from ACCOUNTS
3 where ...
SQL> select /*+ INDEX(scott.accounts) */
2 from SCOTT.ACCOUNTS
3 where ...
SQL> select /* INDEX(A) */
2 from SCOTT.ACCOUNTS A
3 where ...

... the (in)famous ignore issue
335

336
SQL> select *
2 from emp e,
3 dept d
5 and d.dname = 'SALES';
--------------------------------------------------------
--------------------------------------------------------
| 1 | MERGE JOIN | | 5 |
|* 2 | TABLE ACCESS BY INDEX ROWID| DEPT | 1 |
| 3 | INDEX FULL SCAN | PK_DEPT | 4 |
|* 4 | SORT JOIN | | 14 |
| 5 | TABLE ACCESS FULL | EMP | 14 |
--------------------------------------------------------

338
SQL> select /*+ use_hash(d) */ *
2 from emp e,
3 dept d
--------------------------------------------------------
--------------------------------------------------------
| 1 | MERGE JOIN | | 5 |
|* 4 | SORT JOIN | | 14 |
--------------------------------------------------------

339
/*+ use_hash(d) */
if joining into "d"...
use a hash join

341
--------------------------------------------------------
--------------------------------------------------------
| 1 | MERGE JOIN | | 5 |
|* 4 | SORT JOIN | | 14 |
--------------------------------------------------------

342
if joining into "d"...
we must be starting with "e"

343
SQL> select /*+ leading(e) use_hash(d) */ *
2 from emp e,
3 dept d
---------------------------------------------------
| Id | Operation | Name | Rows | Bytes |
---------------------------------------------------
| 0 | SELECT STATEMENT | | 5 | 285 |
|* 1 | HASH JOIN | | 5 | 285 |
| 2 | TABLE ACCESS FULL| EMP | 14 | 518 |
|* 3 | TABLE ACCESS FULL| DEPT | 1 | 20 |
---------------------------------------------------

345
"hints are like violence…
if they do not work, use more"

346
SQL> select /*+ leading(e d b) use_hash(d) use_hash(b) */ *
2 from emp e,
3 dept d,
4 bonus b
6 and d.dname = 'SALES'
7 and e.ename = b.ename;
---------------------------------------------
---------------------------------------------
|* 1 | HASH JOIN | | 1 |
|* 2 | HASH JOIN | | 5 |
| 3 | TABLE ACCESS FULL| EMP | 14 |
|* 4 | TABLE ACCESS FULL| DEPT | 1 |
| 5 | TABLE ACCESS FULL | BONUS | 1 |
---------------------------------------------

347
SQL> select /*+ leading(e d b) use_hash(d) use_hash(b) */ *
2 from emp e,
3 dept d,
4 bonus b
---------------------------------------------
---------------------------------------------
|* 1 | HASH JOIN | | 1 |
|* 3 | HASH JOIN | | 5 |
---------------------------------------------

348
---------------------------------------------
---------------------------------------------
|* 1 | HASH JOIN | | 1 |
|* 2 | HASH JOIN | | 5 |
---------------------------------------------
---------------------------------------------
---------------------------------------------
|* 1 | HASH JOIN | | 1 |
|* 3 | HASH JOIN | | 5 |
---------------------------------------------

350
SQL> select /*+ leading(e d b)
2 use_hash(d)
3 use_hash(b)
4 no_swap_join_inputs(b)
5 */
6 *
7 from emp e,
8 dept d,
9 bonus b

352
/*+ no_swap_join_inputs (b) */

355
SQL> SELECT *
2 from table(dbms_xplan.display(.... ,
format=>'typical +OUTLINE))
/*+ BEGIN_OUTLINE_DATA
USE_HASH(@"SEL$1" "B"@"SEL$1")
USE_HASH(@"SEL$1" "D"@"SEL$1")
LEADING(@"SEL$1" "E"@"SEL$1" "D"@"SEL$1" "B"@"SEL$1")
FULL(@"SEL$1" "B"@"SEL$1")
FULL(@"SEL$1" "D"@"SEL$1")
FULL(@"SEL$1" "E"@"SEL$1")
OUTLINE_LEAF(@"SEL$1")
ALL_ROWS
DB_VERSION('11.2.0.2')
OPTIMIZER_FEATURES_ENABLE('11.2.0.2')
IGNORE_OPTIM_EMBEDDED_HINTS
END_OUTLINE_DATA
*/ Ack: M.Colgan
swap still possible !

just hints … better in 12c
358

363
SQL> select *
2 from SALES
3 where SALES_DATE > ...

365
SQL> create index SALES_IX
2 on SALES( SALES_DATE );
Index created.

366
SQL> explain plan for
2 select * from SALES
3 where sales_date > ...;
--------------------------------------------------------
--------------------------------------------------------
| 1 | TABLE ACCESS BY INDEX ROWID| SALES | 950 |
|* 2 | INDEX RANGE SCAN | SALES_IX | 950 |
--------------------------------------------------------

372
SQL> create table T
2 as select * from all_objects;
Table created.
SQL> create index OBJ_IX on T ( OBJECT_ID);
Index created.
SQL> analyze table T estimate statistics;
Table analyzed.

373
SQL> select * from T
2 where OWNER = 'SCOTT'
3 and created > sysdate - 1
4 /
---------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
---------------------------------------------------------------
| 0 | SELECT STATEMENT | | 6 | 546 | 281 (1)|
|* 1 | TABLE ACCESS FULL| T | 6 | 546 | 281 (1)|
---------------------------------------------------------------

375
SQL> create index NEW_IX on T ( owner);
Index created.
2 where OWNER = 'SCOTT'
3 and created > sysdate - 1;
---------------------------------------------------------------------------
---------------------------------------------------------------------------
|* 1 | TABLE ACCESS BY INDEX ROWID| T | 6 | 546 | 122 (0)|
|* 2 | INDEX RANGE SCAN | NEW_IX | 4107 | | 10 (0)|
---------------------------------------------------------------------------

378
2 where OWNER = 'SYS'
3 and OBJECT_ID between 10 and 8000
4 /
---------------------------------------------------------------------------
---------------------------------------------------------------------------
|* 2 | INDEX RANGE SCAN | OBJ_IX | 7851 | | 20 (0)|
---------------------------------------------------------------------------

379
2 where owner = 'SYS'
3 and object_id between 10 and 8000
4 /
4967 rows selected.
Statistics
-----------------------------------------------------
0 recursive calls
0 db block gets
784 consistent gets
15 physical reads

381
4 /
---------------------------------------------------------------------------
---------------------------------------------------------------------------
|* 2 | INDEX RANGE SCAN | NEW_IX | 4105 | | 10 (0)|
---------------------------------------------------------------------------
changed !

382
4 /
4967 rows selected.
Statistics
------------------------------------------------------
0 recursive calls
0 db block gets
1522 consistent gets
62 physical reads

384
SQL> alter index OWN_IX invisible;
Index altered.

385
SQL> alter session set
2 optimizer_use_invisible_indexes = true;
Session altered.
SQL> [MY QUERY]
SQL> alter session set
2 optimizer_use_invisible_indexes = false;
Session altered.

if you are tuning SQL ...
387
... you are failing

tuning the user experience
388

389
find
stop
side effects
cure

ORA-03113
connormcdonald.wordpress.com

SQL Tuning 101 - Sep 2013

More Related Content

What's hot

Viewers also liked

Similar to SQL Tuning 101 - Sep 2013

More from Connor McDonald

Recently uploaded

SQL Tuning 101 - Sep 2013