SQL> drop table test purge;
Table dropped.
SQL> create table test as select * from dba_objects;
Table created.
SQL> select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in ('TEST')
and owner = 'TEST'
and (stale_stats = 'YES' or last_analyzed is null); 2 3 4 5
OWNER NAME OBJECT_TYPE STA LAST_ANAL
------------------------------ ------------------------------ ------------ --- ---------
TEST TEST TABLE
开始搜集统计信息:
SQL> select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in ('TEST')
and owner = 'TEST'
and (stale_stats = 'YES' or last_analyzed is null); 2 3 4 5
OWNER NAME OBJECT_TYPE STA LAST_ANAL
------------------------------ ------------------------------ ------------ --- ---------
TEST TEST TABLE
SQL> BEGIN
DBMS_STATS.GATHER_TABLE_STATS(ownname => 'TEST',
tabname => 'TEST',
estimate_percent => 100,
method_opt => 'for all columns size repeat',
no_invalidate => FALSE,
degree => 8,
cascade => TRUE);
END;
2 3 4 5 6 7 8 9 10 /
PL/SQL procedure successfully completed.
SQL> select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in ('TEST')
and owner = 'TEST'
and (stale_stats = 'YES' or last_analyzed is null); 2 3 4 5
no rows selected
删除10%的数据:
SQL> select count(*) from test;
COUNT(*)
----------
72530
SQL> delete from test where rownum<=72530*0.1;
7253 rows deleted.
SQL> commit;
Commit complete.
SQL> select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in ('TEST')
and owner = 'TEST'
and (stale_stats = 'YES' or last_analyzed is null); 2 3 4 5
no rows selected
SQL> exec dbms_stats.flush_database_monitoring_info; ---数据输入磁盘
PL/SQL procedure successfully completed.
SQL> select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in ('TEST')
and owner = 'TEST'
and (stale_stats = 'YES' or last_analyzed is null); 2 3 4 5
no rows selected
SQL> delete from test where rownum<=72530*0.3;
21759 rows deleted.
SQL> commit;
Commit complete.
SQL> select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in ('TEST')
and owner = 'TEST'
and (stale_stats = 'YES' or last_analyzed is null); 2 3 4 5
no rows selected
SQL> exec dbms_stats.flush_database_monitoring_info;
PL/SQL procedure successfully completed.
SQL> select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in ('TEST')
and owner = 'TEST'
and (stale_stats = 'YES' or last_analyzed is null); 2 3 4 5
OWNER NAME OBJECT_TYPE STA LAST_ANAL
------------------------------ ------------------------------ ------------ --- ---------
TEST TEST TABLE YES 15-JAN-01
怎么样才算统计信息过期,是不是 表中有 10% 的数据变化了。
---查看表的采样率:
SELECT owner,
table_name,
num_rows,
sample_size,
trunc(sample_size / num_rows * 100) estimate_percent
FROM DBA_TAB_STATISTICS
WHERE owner='SCOTT' AND table_name='TEST';
有时候收集统计信息不会设置这个参数，method_opt
---------------------------------------------------------
SQL> create table test as select * from dba_objects;
Table created.
SQL> EXEC DBMS_STATS.gather_table_stats('TEST','TEST');
PL/SQL procedure successfully completed.
SQL> select a.column_name,
b.num_rows,
a.num_distinct Cardinality,
round(a.num_distinct / b.num_rows * 100, 2) selectivity,
a.histogram,
a.num_buckets
from dba_tab_col_statistics a, dba_tables b
where a.owner = b.owner
and a.table_name = b.table_name
and a.owner = 'TEST'
and a.table_name = 'TEST';
2 3 4 5 6 7 8 9 10 11
COLUMN_NAME NUM_ROWS CARDINALITY SELECTIVITY HISTOGRAM NUM_BUCKETS
------------------------------ ---------- ----------- ----------- --------------- -----------
OWNER 72530 30 .04 NONE 1
OBJECT_NAME 72530 43728 60.29 NONE 1
SUBOBJECT_NAME 72530 114 .16 NONE 1
OBJECT_ID 72530 72530 100 NONE 1
DATA_OBJECT_ID 72530 7687 10.6 NONE 1
OBJECT_TYPE 72530 44 .06 NONE 1
CREATED 72530 1093 1.51 NONE 1
LAST_DDL_TIME 72530 1143 1.58 NONE 1
TIMESTAMP 72530 1214 1.67 NONE 1
STATUS 72530 2 0 NONE 1
TEMPORARY 72530 2 0 NONE 1
COLUMN_NAME NUM_ROWS CARDINALITY SELECTIVITY HISTOGRAM NUM_BUCKETS
------------------------------ ---------- ----------- ----------- --------------- -----------
GENERATED 72530 2 0 NONE 1
SECONDARY 72530 2 0 NONE 1
NAMESPACE 72530 21 .03 NONE 1
EDITION_NAME 72530 0 0 NONE 0
15 rows selected.
SQL> SELECT owner,
table_name,
num_rows,
sample_size,
trunc(sample_size / num_rows * 100) estimate_percent
FROM DBA_TAB_STATISTICS
WHERE owner='SCOTT' AND table_name='TEST'; 2 3 4 5 6 7
OWNER TABLE_NAME NUM_ROWS SAMPLE_SIZE ESTIMATE_PERCENT
------------------------------ ------------------------------ ---------- ----------- ----------------
SCOTT TEST 72606 72606 100
默认大表30%,小表100%
SQL> select count(*) from test where owner='SYS';
COUNT(*)
----------
30795
SQL> EXEC DBMS_STATS.gather_table_stats('TEST','TEST');
PL/SQL procedure successfully completed.
SQL> select a.column_name,
b.num_rows,
a.num_distinct Cardinality,
round(a.num_distinct / b.num_rows * 100, 2) selectivity,
a.histogram,
a.num_buckets
from dba_tab_col_statistics a, dba_tables b
where a.owner = b.owner
and a.table_name = b.table_name
and a.owner = 'TEST'
and a.table_name = 'TEST';
2 3 4 5 6 7 8 9 10 11
COLUMN_NAME NUM_ROWS CARDINALITY SELECTIVITY HISTOGRAM NUM_BUCKETS
------------------------------ ---------- ----------- ----------- --------------- -----------
OWNER 72530 30 .04 FREQUENCY 24
OBJECT_NAME 72530 43728 60.29 NONE 1
SUBOBJECT_NAME 72530 114 .16 NONE 1
OBJECT_ID 72530 72530 100 NONE 1
DATA_OBJECT_ID 72530 7687 10.6 NONE 1
OBJECT_TYPE 72530 44 .06 NONE 1
CREATED 72530 1093 1.51 NONE 1
LAST_DDL_TIME 72530 1143 1.58 NONE 1
TIMESTAMP 72530 1214 1.67 NONE 1
STATUS 72530 2 0 NONE 1
TEMPORARY 72530 2 0 NONE 1
COLUMN_NAME NUM_ROWS CARDINALITY SELECTIVITY HISTOGRAM NUM_BUCKETS
------------------------------ ---------- ----------- ----------- --------------- -----------
GENERATED 72530 2 0 NONE 1
SECONDARY 72530 2 0 NONE 1
NAMESPACE 72530 21 .03 NONE 1
EDITION_NAME 72530 0 0 NONE 0
15 rows selected.
默认是AUTO 默认的 opt_method 是auto
默认的 采样率 会根据 表大小变化
exec dbms_stats.flush_database_monitoring_info; ----刷新信息到磁盘
--------------EXPLAIN PLAN FOR SQL, 然后执行下面语句得到表名字---------------------------
select '''' || object_owner || '''', '''' || object_name || ''','
from plan_table
where object_type = 'TABLE'
union
---table in the index---------
select '''' || table_owner || '''', '''' || table_name || '*'','
from dba_indexes
where owner in
(select distinct object_owner from plan_table where rownum > 0)
and index_name in
(select distinct object_name from plan_table where rownum > 0)
order by 2;
--------------再把上面的结果贴入下面代码-------------------------------------------------
select owner, table_name name, object_type, stale_stats, last_analyzed
from dba_tab_statistics
where table_name in
(
table_name
)
and owner='owner'
and (stale_stats = 'YES' or last_analyzed is null);
我现在要查看它怎么过期了
select *
from all_tab_modifications
where table_owner='&owner'
and table_name in
(
'TEST'
)
and (inserts > 0 or updates > 0 or deletes > 0)
order by table_name;