Oracle12c新特性之如何检测有用的多列统计信息详解

SQL> select banner from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE 12.1.0.2.0 Production
TNS for Linux: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production

SQL> 
SQL> conn sh/sh@HOEGH
Connected.
SQL> 
SQL> DROP TABLE customers_test;
DROP TABLE customers_test
  *
ERROR at line 1:
ORA-00942: table or view does not exist


SQL> CREATE TABLE customers_test AS SELECT * FROM customers;

Table created.

SQL> select count(*) from customers_test;

 COUNT(*)
----------
 55500

SQL>

SQL> 
SQL> EXEC DBMS_STATS.GATHER_TABLE_STATS(user, 'customers_test');

PL/SQL procedure successfully completed.

SQL>

SQL> show user
USER is “SYS”
SQL> BEGIN
 DBMS_STATS.SEED_COL_USAGE(null,null,300);
END;
/ 2 3 4

PL/SQL procedure successfully completed.
SQL>

SQL> 
SQL> EXPLAIN PLAN FOR
 SELECT *
 FROM customers_test
 WHERE cust_city = 'Los Angeles'
 AND cust_state_province = 'CA'
 AND country_id = 52790; 2 3 4 5 6 

Explained.

SQL> 
SQL> SELECT PLAN_TABLE_OUTPUT 
FROM TABLE(DBMS_XPLAN.DISPLAY('plan_table', null,'basic rows')); 2 

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 2112738156

----------------------------------------------------
| Id | Operation | Name | Rows |
----------------------------------------------------
| 0 | SELECT STATEMENT |  | 1 |
| 1 | TABLE ACCESS FULL| CUSTOMERS_TEST | 1 |
----------------------------------------------------

8 rows selected.

SQL>

SQL> 
SQL> SET LONG 100000
SQL> SET LINES 120
SQL> SET PAGES 0
SQL> SELECT DBMS_STATS.REPORT_COL_USAGE(user, 'customers_test')
 2 FROM DUAL;
LEGEND:
.......

EQ : Used in single table EQuality predicate
RANGE : Used in single table RANGE predicate
LIKE : Used in single table LIKE predicate
NULL : Used in single table is (not) NULL predicate
EQ_JOIN : Used in EQuality JOIN predicate
NONEQ_JOIN : Used in NON EQuality JOIN predicate
FILTER : Used in single table FILTER predicate
JOIN : Used in JOIN predicate
GROUP_BY : Used in GROUP BY expression
...............................................................................

###############################################################################

COLUMN USAGE REPORT FOR SH.CUSTOMERS_TEST
.........................................

1. COUNTRY_ID  : EQ
2. CUST_CITY  : EQ
3. CUST_STATE_PROVINCE  : EQ
4. (CUST_CITY, CUST_STATE_PROVINCE,
 COUNTRY_ID)  : FILTER
###############################################################################



SQL>

SQL> 
SQL> SELECT DBMS_STATS.CREATE_EXTENDED_STATS(user, 'customers_test') FROM DUAL;
###############################################################################

EXTENSIONS FOR SH.CUSTOMERS_TEST
................................

1. (CUST_CITY, CUST_STATE_PROVINCE,
 COUNTRY_ID)  : SYS_STUMZ$C3AIHLPBROI#SKA58H_N created
###############################################################################



SQL>

SQL> 
SQL> EXEC DBMS_STATS.GATHER_TABLE_STATS(user,'customers_test');

PL/SQL procedure successfully completed.

SQL>

SQL> 
SQL> COL COLUMN_NAME FOR A30
SQL> SELECT COLUMN_NAME, NUM_DISTINCT, HISTOGRAM
FROM USER_TAB_COL_STATISTICS
WHERE TABLE_NAME = 'CUSTOMERS_TEST'
ORDER BY 1; 2 3 4 
COUNTRY_ID   19 FREQUENCY
CUST_CITY  620 HYBRID
CUST_CITY_ID  620 NONE
CUST_CREDIT_LIMIT  8 NONE
CUST_EFF_FROM   1 NONE
CUST_EFF_TO   0 NONE
CUST_EMAIL  1699 NONE
CUST_FIRST_NAME  1300 NONE
CUST_GENDER   2 NONE
CUST_ID  55500 NONE
CUST_INCOME_LEVEL  12 NONE
CUST_LAST_NAME  908 NONE
CUST_MAIN_PHONE_NUMBER  51344 NONE
CUST_MARITAL_STATUS  11 NONE
CUST_POSTAL_CODE  623 NONE
CUST_SRC_ID   0 NONE
CUST_STATE_PROVINCE  145 FREQUENCY
CUST_STATE_PROVINCE_ID  145 NONE
CUST_STREET_ADDRESS  49900 NONE
CUST_TOTAL   1 NONE
CUST_TOTAL_ID   1 NONE
CUST_VALID   2 NONE
CUST_YEAR_OF_BIRTH  75 NONE
SYS_STUMZ$C3AIHLPBROI#SKA58H_N 620 HYBRID

24 rows selected.

SQL>

SQL> 
SQL> EXPLAIN PLAN FOR
 SELECT *
 FROM customers_test
 WHERE cust_city = 'Los Angeles'
 AND cust_state_province = 'CA'
 AND country_id = 52790; 2 3 4 5 6 

Explained.

SQL> 
SQL> SELECT PLAN_TABLE_OUTPUT 
FROM TABLE(DBMS_XPLAN.DISPLAY('plan_table', null,'basic rows')); 2 
Plan hash value: 2112738156

----------------------------------------------------
| Id | Operation | Name | Rows |
----------------------------------------------------
| 0 | SELECT STATEMENT |  | 867 |
| 1 | TABLE ACCESS FULL| CUSTOMERS_TEST | 867 |
----------------------------------------------------

8 rows selected.

SQL>