VIEW PUSHED PREDICATE 原理

<pre name="code" class="sql">SELECT *
FROM (SELECT DISTINCT e.n_event_id,
e.n_parent_id,
e.v_event_num,
em.n_req_type_1,
em.n_req_type_2,
em.v_title,
em.v_description,
e.n_priority,
cb.n_time_limit,
cb.n_status,
e.n_process_way,
e.n_maintaince_event_id,
e.v_maintaince_flag,
e.v_replacedevice_flag,
et.d_acbept_date,
et.d_finish_date,
et.v_exempt_status,
et.n_callback_status,
et.n_delay_time,
erpl.n_creator,
erpl.d_creation_date,
e.n_req_id,
el.v_res_notice_msg,
el.v_res_notice_email,
el.v_res_notice_im,
vd.v_valid_status,
vd.v_related_org_id,
e.n_dev_process_way,
e.v_over_time_reason,
e.v_confirm_person,
e.v_new_device_num
FROM tb_event e,
tb_event_related_person erpl,
vorg_department vd,
tb_callback cb,
tb_event_log el,
tb_event_marker em,
tb_event_track et
WHERE e.n_event_id = et.n_event_id(+)
AND e.n_event_id = em.n_event_id(+)
AND e.n_event_id = el.n_event_id(+)
AND e.n_event_id = cb.n_event_id(+)
AND erpl.n_dept_id = vd.recid(+)
AND e.n_event_id = erpl.n_event_id(+)
ORDER BY e.d_creation_date DESC)
WHERE rownum <= 40;

vorg_department为一个view，具体定义如下：

create or replace view vorg_department as
select d.recid,
r.v_valid_status,
d.v_related_org_id,
r.org_parent,
r.tree_no,
d.dept_kind,
d.dept_type,
d.dept_name,
d.status,
d.dept_code,
d.area_code,
d.dept_prof,
d.sort_num,
d.link_addr,
r.layer
from ORG_DEPARTMENT d, ORG_DEPRELATION r
where d.recid = r.org_child
and r.relation_type = 1


    该语句的执行计划如下：

PLAN_TABLE_OUTPUT

———————————————————————————————————–
| Id  | Operation                     |  Name                 | Rows  | Bytes|TempSpc|Cost|
———————————————————————————————————–
|   0 | SELECT STATEMENT              |                       |     40| 15404|    |  23M|
|*  1 |  COUNT STOPKEY                |                       |       |      |    |     |
|   2 |   VIEW                        |                       |   110M|  395G|    |  23M|
|*  3 |    SORT UNIQUE STOPKEY        |                       |   110M|   27G| 58G|  11M|
|   4 |     NESTED LOOPS OUTER        |                       |   110M|   27G|    | 2797|
|*  5 |      HASH JOIN OUTER          |                       |  1255K|  308M| 39M| 2797|
|*  6 |       HASH JOIN OUTER         |                       |   153K|   37M| 28M| 1873|
|*  7 |        HASH JOIN OUTER        |                       |   115K|   27M| 24M| 1384|
|*  8 |         HASH JOIN OUTER       |                       |   101K|   23M| 23M|  990|
|*  9 |          HASH JOIN OUTER      |                       |   100K|   22M| 17M|  571|
|  10 |           TABLE ACCESS FULL   | TB_EVENT              |  77044|   16M|    |  256|
|  11 |           INDEX FAST FULL SCAN| IDX_EVENT_TRACK_N_E_ID|   100K|  491K|    |    4|
|  12 |          INDEX FAST FULL SCAN |IDX_TB_CALLBAK_E_ID    |  75959|  296K|    |   21|
|  13 |         TABLE ACCESS FULL     | TB_EVENT_MARKER       |   3686| 18430|    |    3|
|* 14 |        INDEX FAST FULL SCAN   | IDX_TB_EVENT_RP_DUP1  |   101K|  895K|    |    4|
|  15 |       INDEX FAST FULL SCAN    |IDX_TB_EVENT_LOG_N_E_ID|   628K| 2455K|    |  149|
|  16 |      VIEW PUSHED PREDICATE    | VORG_DEPARTMENT       |     88| 1144 |    |     |
|  17 |       NESTED LOOPS            |                       |     1 |   15 |    |    2|
|* 18 |        INDEX UNIQUE SCAN    | PK_DEPARTMENT           |     1 |     6|    |    1|
|* 19 |        INDEX RANGE SCAN     | ASSOCIATION8_FK         |     1 |     9|    |    1|

———————————————————————————————————–



这里 tb_event_related_person erpl和 vorg_department vd 关联
AND erpl.n_dept_id = vd.recid(+)


create or replace view vorg_department as

select d.recid,
r.v_valid_status,
d.v_related_org_id,
r.org_parent,
r.tree_no,
d.dept_kind,
d.dept_type,
d.dept_name,
d.status,
d.dept_code,
d.area_code,
d.dept_prof,
d.sort_num,
d.link_addr,
r.layer
from ORG_DEPARTMENT d, ORG_DEPRELATION r
where d.recid = r.org_child
and r.relation_type = 1



谓词推入通过关联列推入,这里把erpl.n_dept_id 推入到vd.recid

对试图通过vd.recid列进行提前过滤

相当于对视图的数据进行提前过滤,谓词推入的主要目的就是让Oracle尽可能早的过滤掉无用的数据，从而提升查询性能。