练习ORACLE统计信息--直方图
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①创建表t
SQL> create table t as select * from dba_objects; Table created. --收集直方图 SQL> exec dbms_stats.gather_table_stats(user,‘T‘); PL/SQL procedure successfully completed. --此时数据库为表上的所有字段收集了缺省的统计信息，每个列两个Bucket： SQL> col column_name for a30 SQL> col owner for a10 SQL> col table_name for a10 SQL> col ENDPOINT_ACTUAL_VALUE for a10 ②查询 SQL> select * from dba_tab_histograms where table_name=‘T‘ and owner=‘SYS‘ order by 3; OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T CREATED 1 2457673.05 SYS T CREATED 0 2456529.48 SYS T DATA_OBJECT_ID 1 88710 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T DATA_OBJECT_ID 0 0 SYS T GENERATED 0 4.0500E+35 SYS T GENERATED 1 4.6211E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T LAST_DDL_TIME 1 2457673.05 SYS T LAST_DDL_TIME 0 2452549.53 SYS T NAMESPACE 0 1 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T NAMESPACE 1 64 SYS T OBJECT_ID 1 88710 SYS T OBJECT_ID 0 2 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_NAME 0 2.4504E+35 SYS T OBJECT_NAME 1 6.2963E+35 SYS T OBJECT_TYPE 0 3.4943E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_TYPE 1 4.5849E+35 SYS T OWNER 0 3.3913E+35 SYS T OWNER 1 4.5831E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T SECONDARY 1 4.6211E+35 SYS T SECONDARY 0 4.0500E+35 SYS T STATUS 1 4.4786E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T STATUS 0 4.4786E+35 SYS T SUBOBJECT_NAME 1 4.5340E+35 SYS T SUBOBJECT_NAME 0 1.8867E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T TEMPORARY 1 4.6211E+35 SYS T TEMPORARY 0 4.0500E+35 SYS T TIMESTAMP 0 2.5558E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T TIMESTAMP 1 2.6059E+35
28 rows selected.
--同时，列的低值、高值等信息会被收集记录在dba_tab_col_statistics中：
SQL> select table_name,column_name,num_distinct,low_value,high_value,DENSITY from dba_tab_col_statistics where owner=‘SYS‘ and table_name=‘T‘; TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- T OWNER 29 415045585F303330323030 584442 .034482759 T OBJECT_NAME 52212 2F31303030333233645F44656C6567617465496E766F636174696F6E4861 794362437253756253616D706C696E67547970653232395F54 .000019153 TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- T SUBOBJECT_NAME 150 2456534E5F31 575248245F5741495453545F3234313436323135355F30 .006666667 T OBJECT_ID 86995 C103 TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- C309580B .000011495 T DATA_OBJECT_ID 9106 80 C309580B .000109818 T OBJECT_TYPE 45 TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- 434C5553544552 584D4C20534348454D41 .022222222 T CREATED 978 787108180C2624 78740A0B02082A .001022495 TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- T LAST_DDL_TIME 1096 78660A010D2A32 78740A0B02082A .000912409 T TIMESTAMP 1130 313939302D30382D32363A31313A32353A3030 323031362D31302D31313A30313A30373A3431 .000884956 TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- T STATUS 1 56414C4944 56414C4944 1 T TEMPORARY 2 4E TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- 59 .5 T GENERATED 2 4E 59 .5 T SECONDARY 2 TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- 4E 59 .5 T NAMESPACE 21 C102 C141 .047619048 TABLE_NAME COLUMN_NAME NUM_DISTINCT ---------- ------------------------------ ------------ LOW_VALUE ---------------------------------------------------------------- HIGH_VALUE DENSITY ---------------------------------------------------------------- ---------- T EDITION_NAME 0 0 15 rows selected. ③SQL> exec dbms_stats.gather_table_stats(user,‘T‘,method_opt=> ‘for all columns size 1‘); PL/SQL procedure successfully completed. SQL> exec dbms_stats.gather_table_stats(user,‘T‘,method_opt=>‘for columns owner size 1‘); PL/SQL procedure successfully completed.
或删除owner字段统计信息，（无用）
--查询发现直方图信息并未被删除
SQL> select * from dba_tab_histograms where table_name=‘T‘ and owner=‘SYS‘ order by 3; OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T CREATED 1 2457673.05 SYS T CREATED 0 2456529.48 SYS T DATA_OBJECT_ID 1 88710 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T DATA_OBJECT_ID 0 0 SYS T GENERATED 0 4.0500E+35 SYS T GENERATED 1 4.6211E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T LAST_DDL_TIME 1 2457673.05 SYS T LAST_DDL_TIME 0 2452549.53 SYS T NAMESPACE 0 1 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T NAMESPACE 1 64 SYS T OBJECT_ID 1 88710 SYS T OBJECT_ID 0 2 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_NAME 0 2.4504E+35 SYS T OBJECT_NAME 1 6.2963E+35 SYS T OBJECT_TYPE 0 3.4943E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_TYPE 1 4.5849E+35 SYS T OWNER 0 3.3913E+35 SYS T OWNER 1 4.5831E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T SECONDARY 1 4.6211E+35 SYS T SECONDARY 0 4.0500E+35 SYS T STATUS 1 4.4786E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T STATUS 0 4.4786E+35 SYS T SUBOBJECT_NAME 1 4.5340E+35 SYS T SUBOBJECT_NAME 0 1.8867E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T TEMPORARY 1 4.6211E+35 SYS T TEMPORARY 0 4.0500E+35 SYS T TIMESTAMP 0 2.5558E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T TIMESTAMP 1 2.6059E+35 28 rows selected. ④使用delete_column_stats可以彻底删除列的柱状图信息： SQL> exec dbms_stats.delete_column_stats(user,‘T‘,‘OWNER‘); PL/SQL procedure successfully completed. --此时查询发现owner字段在直方图中已经删除 SQL> select * from dba_tab_histograms where table_name=‘T‘ and owner=‘SYS‘ order by 3; OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T CREATED 1 2457673.05 SYS T CREATED 0 2456529.48 SYS T DATA_OBJECT_ID 1 88710 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T DATA_OBJECT_ID 0 0 SYS T GENERATED 0 4.0500E+35 SYS T GENERATED 1 4.6211E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T LAST_DDL_TIME 1 2457673.05 SYS T LAST_DDL_TIME 0 2452549.53 SYS T NAMESPACE 1 64 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T NAMESPACE 0 1 SYS T OBJECT_ID 1 88710 SYS T OBJECT_ID 0 2 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_NAME 0 2.4504E+35 SYS T OBJECT_NAME 1 6.2963E+35 SYS T OBJECT_TYPE 1 4.5849E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_TYPE 0 3.4943E+35 SYS T SECONDARY 0 4.0500E+35 SYS T SECONDARY 1 4.6211E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T STATUS 0 4.4786E+35 SYS T STATUS 1 4.4786E+35 SYS T SUBOBJECT_NAME 0 1.8867E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T SUBOBJECT_NAME 1 4.5340E+35 SYS T TEMPORARY 0 4.0500E+35 SYS T TEMPORARY 1 4.6211E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T TIMESTAMP 1 2.6059E+35 SYS T TIMESTAMP 0 2.5558E+35 26 rows selected. ⑤再次收集，owner字段又回来了 SQL> exec dbms_stats.gather_table_stats(user,‘T‘); PL/SQL procedure successfully completed. SQL> select * from dba_tab_histograms where table_name=‘T‘ and owner=‘SYS‘ order by 3; OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T CREATED 1 2457673.05 SYS T CREATED 0 2456529.48 SYS T DATA_OBJECT_ID 1 88710 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T DATA_OBJECT_ID 0 0 SYS T GENERATED 0 4.0500E+35 SYS T GENERATED 1 4.6211E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T LAST_DDL_TIME 1 2457673.05 SYS T LAST_DDL_TIME 0 2452549.53 SYS T NAMESPACE 0 1 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T NAMESPACE 1 64 SYS T OBJECT_ID 1 88710 SYS T OBJECT_ID 0 2 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_NAME 0 2.4504E+35 SYS T OBJECT_NAME 1 6.2963E+35 SYS T OBJECT_TYPE 0 3.4943E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T OBJECT_TYPE 1 4.5849E+35 SYS T OWNER 0 3.3913E+35 SYS T OWNER 1 4.5831E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T SECONDARY 1 4.6211E+35 SYS T SECONDARY 0 4.0500E+35 SYS T STATUS 1 4.4786E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T STATUS 0 4.4786E+35 SYS T SUBOBJECT_NAME 1 4.5340E+35 SYS T SUBOBJECT_NAME 0 1.8867E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T TEMPORARY 1 4.6211E+35 SYS T TEMPORARY 0 4.0500E+35 SYS T TIMESTAMP 0 2.5558E+35 OWNER TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ---------- ---------- ------------------------------ --------------- ENDPOINT_VALUE ENDPOINT_A -------------- ---------- SYS T TIMESTAMP 1 2.6059E+35 28 rows selected. SQL> exec dbms_stats.gather_table_stats(user,‘T‘,method_opt=>‘for columns owner size 1‘); PL/SQL procedure successfully completed.
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