優化前：
select count(t.id)
? from test t
?where t.status = 1
?? and t.id not in (select distinct a.app_id
????????????????????? from test2 a
???????????????????? where a.type = 1
?????????????????????? and a.rule_id in (152, 153, 154))
???????????
? 17:20:57 laojiu>@plan

PLAN_TABLE_OUTPUT
————————————————————————————————————————-
Plan hash value: 684502086

—————————————————————————————-
| Id? | Operation?????????? | Name???????????? | Rows? | Bytes | Cost (%CPU)| Time???? |
—————————————————————————————-
|?? 0 | SELECT STATEMENT??? |????????????????? |???? 1 |??? 18 |?? 176K? (2)| 00:35:23 |
|?? 1 |? SORT AGGREGATE???? |????????????????? |???? 1 |??? 18 |??????????? |????????? |
|*? 2 |?? FILTER??????????? |????????????????? |?????? |?????? |??????????? |????????? |
|*? 3 |??? TABLE ACCESS FULL| test????? |? 1141 | 20538 |?? 845?? (2)| 00:00:11 |
|*? 4 |??? TABLE ACCESS FULL| test2 |???? 1 |??? 12 |?? 309?? (2)| 00:00:04 |
—————————————————————————————-

Predicate Information (identified by operation id):
—————————————————

?? 2 – filter( NOT EXISTS (SELECT /*+ */ 0 FROM “test2” “A” WHERE
????????????? “A”.”type”=1 AND (“A”.”RULE_ID”=152 OR “A”.”RULE_ID”=153 OR
????????????? “A”.”RULE_ID”=154) AND LNNVL(“A”.”APP_ID”<>:B1)))
?? 3 – filter(“T”.”status”=1)
?? 4 – filter(“A”.”type”=1 AND (“A”.”RULE_ID”=152 OR “A”.”RULE_ID”=153 OR
????????????? “A”.”RULE_ID”=154) AND LNNVL(“A”.”APP_ID”<>:B1))
Statistics
———————————————————-
????????? 0? recursive calls
????????? 0? db block gets
????1762169? consistent gets
????????? 0? physical reads
????????? 0? redo size
??????? 519? bytes sent via SQL*Net to client
??????? 492? bytes received via SQL*Net from client
????????? 2? SQL*Net roundtrips to/from client
????????? 0? sorts (memory)
????????? 0? sorts (disk)
????????? 1? rows processed
21 rows selected.

優化后：
?select count(*) from(
?select t.id
?? from test t
? where t.status = 1
?minus
?select distinct a.app_id
?? from test2 a
? where a.type = 1
??? and a.rule_id in (152, 153, 154))
17:23:33 laojiu>@plan

PLAN_TABLE_OUTPUT
————————————————————————————————————————-
Plan hash value: 631655686

————————————————————————————————–
| Id? | Operation???????????? | Name???????????? | Rows? | Bytes |TempSpc| Cost (%CPU)| Time???? |
————————————————————————————————–
|?? 0 | SELECT STATEMENT????? |????????????????? |???? 1 |?????? |?????? |? 1501?? (2)| 00:00:19 |
|?? 1 |? SORT AGGREGATE?????? |????????????????? |???? 1 |?????? |?????? |??????????? |????????? |
|?? 2 |?? VIEW??????????????? |????????????????? |? 1141 |?????? |?????? |? 1501?? (2)| 00:00:19 |
|?? 3 |??? MINUS????????????? |????????????????? |?????? |?????? |?????? |??????????? |????????? |
|?? 4 |???? SORT UNIQUE?????? |????????????????? |? 1141 | 20538 |?????? |?? 846?? (2)| 00:00:11 |
|*? 5 |????? TABLE ACCESS FULL| test????? |? 1141 | 20538 |?????? |?? 845?? (2)| 00:00:11 |
|?? 6 |???? SORT UNIQUE?????? |????????????????? | 69527 |?? 814K|? 3632K|?? 654?? (2)| 00:00:08 |
|*? 7 |????? TABLE ACCESS FULL| test2 | 84140 |?? 986K|?????? |?? 308?? (2)| 00:00:04 |
————————————————————————————————–

Predicate Information (identified by operation id):
—————————————————

?? 5 – filter(“T”.”status”=1)
?? 7 – filter(“A”.”type”=1 AND (“A”.”RULE_ID”=152 OR “A”.”RULE_ID”=153 OR
????????????? “A”.”RULE_ID”=154))

21 rows selected.
Statistics
———————————————————-
????????? 1? recursive calls
????????? 0? db block gets
?????? 2240? consistent gets
????????? 0? physical reads
????????? 0? redo size
??????? 516? bytes sent via SQL*Net to client
??????? 492? bytes received via SQL*Net from client
????????? 2? SQL*Net roundtrips to/from client
????????? 2? sorts (memory)
????????? 0? sorts (disk)
????????? 1? rows processed
在優化sql的時候，我們需要轉變一下思路，等價的改寫sql；

改寫后的sql由于邏輯讀得到了天翻地覆的改變，很快得到結果。

第一條sql執行計劃中有一個函數，LNNVL(“A”.”APP_ID”<>:B1)，lnnvl(exp)

如果exp的結果是false或者是unknown,那么lnnvl返回true;

如果exp的結果是true,返回false.

總結

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