Tsi*_*n D 22 sql oracle partitioning prepared-statement sql-execution-plan
有下一个分区表:
CREATE TABLE "ERMB_LOG_TEST_BF"."OUT_SMS"(
"TRX_ID" NUMBER(19,0) NOT NULL ENABLE,
"CREATE_TS" TIMESTAMP (3) DEFAULT systimestamp NOT NULL ENABLE,
/* other fields... */
) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
STORAGE(BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "ERMB_LOG_TEST_BF"
PARTITION BY RANGE ("TRX_ID") INTERVAL (281474976710656)
(PARTITION "SYS_P1358" VALUES LESS THAN (59109745109237760) SEGMENT CREATION IMMEDIATE
PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255
NOCOMPRESS LOGGING
STORAGE(INITIAL 8388608 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "ERMB_LOG_TEST_BF");
CREATE INDEX "ERMB_LOG_TEST_BF"."OUT_SMS_CREATE_TS_TRX_ID_IX" ON "ERMB_LOG_TEST_BF"."OUT_SMS" ("CREATE_TS" DESC, "TRX_ID" DESC)
PCTFREE 10 INITRANS 2 MAXTRANS 255
STORAGE(
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT) LOCAL
(PARTITION "SYS_P1358"
PCTFREE 10 INITRANS 2 MAXTRANS 255 LOGGING
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "ERMB_LOG_TEST_BF");
我有sql查询,它选择按日期和事务排序的20条记录:
select rd from (
select /*+ INDEX(OUT_SMS OUT_SMS_CREATE_TS_TRX_ID_IX) */ rowid rd
from OUT_SMS
where TRX_ID between 34621422135410688 and 72339069014638591
and CREATE_TS between to_timestamp('2013-02-01 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
and to_timestamp('2013-03-06 08:57:00', 'yyyy-mm-dd hh24:mi:ss')
order by CREATE_TS DESC, TRX_ID DESC
) where rownum <= 20
Oracle已经制定了下一个计划:
-----------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time | Pstart| Pstop |
-----------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 20 | 240 | | 4788K (1)| 00:05:02 | | |
|* 1 | COUNT STOPKEY | | | | | | | | |
| 2 | VIEW | | 312M| 3576M| | 4788K (1)| 00:05:02 | | |
|* 3 | SORT ORDER BY STOPKEY | | 312M| 9G| 12G| 4788K (1)| 00:05:02 | | |
| 4 | PARTITION RANGE ITERATOR| | 312M| 9G| | 19 (0)| 00:00:01 | 1 | 48 |
|* 5 | COUNT STOPKEY | | | | | | | | |
|* 6 | INDEX RANGE SCAN | OUT_SMS_CREATE_TS_TRX_ID_IX | 312M| 9G| | 19 (0)| 00:00:01 | 1 | 48 |
-----------------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<=20)
3 - filter(ROWNUM<=20)
5 - filter(ROWNUM<=20)
6 - access(SYS_OP_DESCEND("CREATE_TS")>=HEXTORAW('878EFCF9F6C5FEFAFF') AND
SYS_OP_DESCEND("TRX_ID")>=HEXTORAW('36F7E7D7F8A4F0BFA9A3FF') AND
SYS_OP_DESCEND("CREATE_TS")<=HEXTORAW('878EFDFEF8FEF8FF') AND
SYS_OP_DESCEND("TRX_ID")<=HEXTORAW('36FBD0E9D4E9DBD5F8A6FF') )
filter(SYS_OP_UNDESCEND(SYS_OP_DESCEND("CREATE_TS"))<=TIMESTAMP' 2013-03-06 08:57:00,000000000' AND
SYS_OP_UNDESCEND(SYS_OP_DESCEND("TRX_ID"))<=72339069014638591 AND
SYS_OP_UNDESCEND(SYS_OP_DESCEND("TRX_ID"))>=34621422135410688 AND
SYS_OP_UNDESCEND(SYS_OP_DESCEND("CREATE_TS"))>=TIMESTAMP' 2013-02-01 00:00:00,000000000')
它完美地运作.
顺便说一下,表OUT_SMS是按字段分区的,TRX_ID并且OUT_SMS_CREATE_TS_TRX_ID_IX是每个分区上的本地索引 (CREATE_TS DESC, TRX_ID DESC).
但是,如果我将此查询转换为预准备语句:
select rd from (
select /*+ INDEX(OUT_SMS OUT_SMS_CREATE_TS_TRX_ID_IX) */ rowid rd
from OUT_SMS
where TRX_ID between ? and ?
and CREATE_TS between ? and ?
order by CREATE_TS DESC, TRX_ID DESC
) where rownum <= 20
Oracle生成下一个计划:
----------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 20 | 240 | 14743 (1)| 00:00:01 | | |
|* 1 | COUNT STOPKEY | | | | | | | |
| 2 | VIEW | | 1964 | 23568 | 14743 (1)| 00:00:01 | | |
|* 3 | SORT ORDER BY STOPKEY | | 1964 | 66776 | 14743 (1)| 00:00:01 | | |
|* 4 | FILTER | | | | | | | |
| 5 | PARTITION RANGE ITERATOR| | 1964 | 66776 | 14742 (1)| 00:00:01 | KEY | KEY |
|* 6 | INDEX RANGE SCAN | OUT_SMS_CREATE_TS_TRX_ID_IX | 1964 | 66776 | 14742 (1)| 00:00:01 | KEY | KEY |
----------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<=20)
3 - filter(ROWNUM<=20)
4 - filter(TO_TIMESTAMP(:RR,'yyyy-mm-dd hh24:mi:ss')<=TO_TIMESTAMP(:T,'yyyy-mm-dd hh24:mi:ss') AND
TO_NUMBER(:ABC)<=TO_NUMBER(:EBC))
6 - access(SYS_OP_DESCEND("CREATE_TS")>=SYS_OP_DESCEND(TO_TIMESTAMP(:T,'yyyy-mm-dd hh24:mi:ss')) AND
SYS_OP_DESCEND("TRX_ID")>=SYS_OP_DESCEND(TO_NUMBER(:EBC)) AND
SYS_OP_DESCEND("CREATE_TS")<=SYS_OP_DESCEND(TO_TIMESTAMP(:RR,'yyyy-mm-dd hh24:mi:ss')) AND
SYS_OP_DESCEND("TRX_ID")<=SYS_OP_DESCEND(TO_NUMBER(:ABC)))
filter(SYS_OP_UNDESCEND(SYS_OP_DESCEND("TRX_ID"))>=TO_NUMBER(:ABC) AND
SYS_OP_UNDESCEND(SYS_OP_DESCEND("TRX_ID"))<=TO_NUMBER(:EBC) AND
SYS_OP_UNDESCEND(SYS_OP_DESCEND("CREATE_TS"))>=TO_TIMESTAMP(:RR,'yyyy-mm-dd hh24:mi:ss') AND
SYS_OP_UNDESCEND(SYS_OP_DESCEND("CREATE_TS"))<=TO_TIMESTAMP(:T,'yyyy-mm-dd hh24:mi:ss'))
操作COUNT STOPKEY从计划中消失.此操作应该在分析索引之后,从第一个查询中获取每个分区的20行.
如何编写准备好的声明以在计划中包含COUNT STOPKEY？
Chr*_*xon 10
使用绑定变量时,Oracle被迫使用动态分区修剪而不是静态分区修剪.结果是Oracle在分析时不知道将访问哪些分区,因为这会根据您的输入变量而变化.
这意味着当使用文字值(而不是绑定变量)时,我们知道本地索引将访问哪些分区.因此,count stopkey在修剪分区之前,可以将其应用于索引的输出.
使用绑定变量时,partition range iterator必须确定要访问的分区.然后进行检查以确保两个操作之间的第一个变量实际上具有较低的值,然后是第二个(filter第二个计划中的操作).
这可以很容易地重现,如下面的测试用例所示:
create table tab (
x date,
y integer,
filler varchar2(100)
) partition by range(x) (
partition p1 values less than (date'2013-01-01'),
partition p2 values less than (date'2013-02-01'),
partition p3 values less than (date'2013-03-01'),
partition p4 values less than (date'2013-04-01'),
partition p5 values less than (date'2013-05-01'),
partition p6 values less than (date'2013-06-01')
);
insert into tab (x, y)
select add_months(trunc(sysdate, 'y'), mod(rownum, 5)), rownum, dbms_random.string('x', 50)
from dual
connect by level <= 1000;
create index i on tab(x desc, y desc) local;
exec dbms_stats.gather_table_stats(user, 'tab', cascade => true);
explain plan for
SELECT * FROM (
SELECT rowid FROM tab
where x between date'2013-01-01' and date'2013-02-02'
and y between 50 and 100
order by x desc, y desc
)
where rownum <= 5;
SELECT * FROM table(dbms_xplan.display(null, null, 'BASIC +ROWS +PARTITION'));
--------------------------------------------------------------------
| Id | Operation | Name | Rows | Pstart| Pstop |
--------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | |
| 1 | COUNT STOPKEY | | | | |
| 2 | VIEW | | 1 | | |
| 3 | SORT ORDER BY STOPKEY | | 1 | | |
| 4 | PARTITION RANGE ITERATOR| | 1 | 2 | 3 |
| 5 | COUNT STOPKEY | | | | |
| 6 | INDEX RANGE SCAN | I | 1 | 2 | 3 |
--------------------------------------------------------------------
explain plan for
SELECT * FROM (
SELECT rowid FROM tab
where x between to_date(:st, 'dd/mm/yyyy') and to_date(:en, 'dd/mm/yyyy')
and y between :a and :b
order by x desc, y desc
)
where rownum <= 5;
SELECT * FROM table(dbms_xplan.display(null, null, 'BASIC +ROWS +PARTITION'));
---------------------------------------------------------------------
| Id | Operation | Name | Rows | Pstart| Pstop |
---------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | |
| 1 | COUNT STOPKEY | | | | |
| 2 | VIEW | | 1 | | |
| 3 | SORT ORDER BY STOPKEY | | 1 | | |
| 4 | FILTER | | | | |
| 5 | PARTITION RANGE ITERATOR| | 1 | KEY | KEY |
| 6 | INDEX RANGE SCAN | I | 1 | KEY | KEY |
---------------------------------------------------------------------
在您的示例中,第二个查询只能将分区过滤到keyat at parse time,而不是像第一个示例中那样过滤分区.
这是少数情况之一,其中文字值可以提供比绑定变量更好的性能.您应该调查这是否可能.
最后,您说您希望每个分区有20行.你的查询不会这样做,它只会根据你的订单返回前20行.对于20行/分区,您需要执行以下操作:
select rd from (
select rowid rd,
row_number() over (partition by trx_id order by create_ts desc) rn
from OUT_SMS
where TRX_ID between ? and ?
and CREATE_TS between ? and ?
order by CREATE_TS DESC, TRX_ID DESC
) where rn <= 20
UPDATE
你没有得到的原因count stopkey是与filter"坏"计划第4行的操作有关.如果重复上面的示例,但没有分区,则可以更清楚地看到这一点.
这为您提供了以下计划:
----------------------------------------
| Id | Operation | Name |
----------------------------------------
| 0 | SELECT STATEMENT | |
|* 1 | COUNT STOPKEY | |
| 2 | VIEW | |
|* 3 | SORT ORDER BY STOPKEY| |
|* 4 | TABLE ACCESS FULL | TAB |
----------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<=5)
3 - filter(ROWNUM<=5)
4 - filter("X">=TO_DATE(' 2013-01-01 00:00:00', 'syyyy-mm-dd
hh24:mi:ss') AND "X"<=TO_DATE(' 2013-02-02 00:00:00', 'syyyy-mm-dd
hh24:mi:ss') AND "Y">=50 AND "Y"<=100)
----------------------------------------
| Id | Operation | Name |
----------------------------------------
| 0 | SELECT STATEMENT | |
|* 1 | COUNT STOPKEY | |
| 2 | VIEW | |
|* 3 | SORT ORDER BY STOPKEY| |
|* 4 | FILTER | |
|* 5 | TABLE ACCESS FULL | TAB |
----------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<=5)
3 - filter(ROWNUM<=5)
4 - filter(TO_NUMBER(:A)<=TO_NUMBER(:B) AND
TO_DATE(:ST,'dd/mm/yyyy')<=TO_DATE(:EN,'dd/mm/yyyy'))
5 - filter("Y">=TO_NUMBER(:A) AND "Y"<=TO_NUMBER(:B) AND
"X">=TO_DATE(:ST,'dd/mm/yyyy') AND "X"<=TO_DATE(:EN,'dd/mm/yyyy'))
如您所见,filter当您使用出现在之前的绑定变量时,会有一个额外的操作sort order by stopkey.访问索引后会发生这种情况.这是检查变量的值是否允许返回数据(中间的第一个变量实际上具有比第二个更低的值).使用文字时不需要这样做,因为优化器已经知道50小于100(在这种情况下).它不知道:a是否小于:b在分析时.
为什么这是我不知道的.它可能是Oracle的有意设计 - 如果为变量设置的值导致零行 - 或者仅仅是疏忽,则无需执行stopkey检查.
我可以在11.2.0.3上重现你的发现.这是我的测试用例:
SQL> -- Table with 100 partitions of 100 rows
SQL> CREATE TABLE out_sms
2 PARTITION BY RANGE (trx_id)
3 INTERVAL (100) (PARTITION p0 VALUES LESS THAN (0))
4 AS
5 SELECT ROWNUM trx_id,
6 trunc(SYSDATE) + MOD(ROWNUM, 50) create_ts
7 FROM dual CONNECT BY LEVEL <= 10000;
Table created
SQL> CREATE INDEX OUT_SMS_IDX ON out_sms (create_ts desc, trx_id desc) LOCAL;
Index created
[static plan]
SELECT rd
FROM (SELECT /*+ INDEX(OUT_SMS OUT_SMS_IDX) */
rowid rd
FROM out_sms
WHERE create_ts BETWEEN systimestamp AND systimestamp + 10
AND trx_id BETWEEN 1 AND 500
ORDER BY create_ts DESC, trx_id DESC)
WHERE rownum <= 20;
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Pstart| Pstop |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | |
|* 1 | COUNT STOPKEY | | | | |
| 2 | VIEW | | 1 | | |
|* 3 | SORT ORDER BY STOPKEY | | 1 | | |
| 4 | PARTITION RANGE ITERATOR| | 1 | 2 | 7 |
|* 5 | COUNT STOPKEY | | | | |
|* 6 | INDEX RANGE SCAN | OUT_SMS_IDX | 1 | 2 | 7 |
---------------------------------------------------------------------------
[dynamic]
----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Pstart| Pstop |
----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | |
|* 1 | COUNT STOPKEY | | | | |
| 2 | VIEW | | 1 | | |
|* 3 | SORT ORDER BY STOPKEY | | 1 | | |
|* 4 | FILTER | | | | |
| 5 | PARTITION RANGE ITERATOR| | 1 | KEY | KEY |
|* 6 | INDEX RANGE SCAN | OUT_SMS_IDX | 1 | KEY | KEY |
----------------------------------------------------------------------------
如在示例中,ROWNUM谓词被推内部分区索引范围扫描在第一种情况下,而不是在第二种情况.使用静态变量时,计划显示Oracle每个分区仅获取20行,而使用动态变量时,Oracle将获取满足每个分区中子句的所有行WHERE.我找不到设置或统计配置,其中使用绑定变量时可以推送谓词.
我希望您可以使用具有更宽静态限制的动态过滤器来对系统进行游戏,但似乎ROWNUM只要存在动态变量,谓词就不会在单个分区内使用:
SELECT rd
FROM (SELECT /*+ INDEX(OUT_SMS OUT_SMS_IDX) */
rowid rd
FROM out_sms
WHERE nvl(create_ts+:5, sysdate) BETWEEN :1 AND :2
AND nvl(trx_id+:6, 0) BETWEEN :3 AND :4
AND trx_id BETWEEN 1 AND 500
AND create_ts BETWEEN systimestamp AND systimestamp + 10
ORDER BY create_ts DESC, trx_id DESC)
WHERE rownum <= 20
Plan hash value: 2740263591
----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Pstart| Pstop |
----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | |
|* 1 | COUNT STOPKEY | | | | |
| 2 | VIEW | | 1 | | |
|* 3 | SORT ORDER BY STOPKEY | | 1 | | |
|* 4 | FILTER | | | | |
| 5 | PARTITION RANGE ITERATOR| | 1 | 2 | 7 |
|* 6 | INDEX RANGE SCAN | OUT_SMS_IDX | 1 | 2 | 7 |
----------------------------------------------------------------------------
如果此查询很重要且其性能至关重要,则可以将索引转换为全局索引.它将增加分区维护,但大多数分区操作可以在线使用最新的Oracle版本.在这种情况下,全局索引将与标准的非分区表一样工作:
SQL> drop index out_sms_idx;
Index dropped
SQL> CREATE INDEX OUT_SMS_IDX ON out_sms (create_ts DESC, trx_id desc);
Index created
SELECT rd
FROM (SELECT
rowid rd
FROM out_sms
WHERE create_ts BETWEEN :1 AND :2
AND trx_id BETWEEN :3 AND :4
ORDER BY create_ts DESC, trx_id DESC)
WHERE rownum <= 20
------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)|
------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 12 | 2 (0)|
|* 1 | COUNT STOPKEY | | | | |
| 2 | VIEW | | 1 | 12 | 2 (0)|
|* 3 | FILTER | | | | |
|* 4 | INDEX RANGE SCAN| OUT_SMS_IDX | 1 | 34 | 2 (0)|
------------------------------------------------------------------------
动态 SQL 是一种选择吗？这样您就可以“注入”TRX_ID 和 CREATE_TS 过滤器值，从而消除绑定变量的使用。也许生成的计划将包括 COUNT STOPKEY。
通过动态 SQL，我的意思是让您动态构建 SQL，然后使用 EXECUTE IMMEDIATE 或 OPEN 调用它。通过使用它，您可以直接使用过滤器而无需绑定变量。例子：
v_sql VARCHAR2(1000) :=
'select rd from (
select /*+ INDEX(OUT_SMS OUT_SMS_CREATE_TS_TRX_ID_IX) */ rowid rd
from OUT_SMS
where TRX_ID between ' || v_trx_id_min || ' and ' || v_trx_id_maxb || '
and CREATE_TS between ' || v_create_ts_min|| ' and ' || v_create_ts_max || '
order by CREATE_TS DESC, TRX_ID DESC
) where rownum <= 20';
然后使用以下方法调用它：
EXECUTE IMMEDIATE v_sql;
甚至：
OPEN cursor_out FOR v_sql;
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