大家好 :) 我有两个表，每个表大约有 3000 万行，我正在寻求在执行计数时提高性能。
这是查询：
SELECT count(*)
FROM VEHICULE v
JOIN CLIENT c ON c.CL_ID = v.VE_CL_ID
WHERE v.VE_BRAND = 'MITSUBISHI'
AND c.CL_COUNTRY = 'SPAIN';
外键在 VEHICULE 表中声明
CONSTRAINT "VEHICULE_CLIENT_FK" FOREIGN KEY ("VE_CL_ID")
REFERENCES "MY_SCHEMA"."CLIENT" ("CL_ID") ENABLE
外键上有一个索引：
CREATE INDEX "MY_SCHEMA"."VEHICULE_INDEX_CLIENT" ON "MY_SCHEMA"."VEHICULE" ("CL_ID")
用于搜索条件的列上也有索引。
请求最多可能需要 40 秒。我已经查看了位图连接索引，但我不知道它是否会有所帮助，因为位图连接应该用于具有低基数的列。这是连接的唯一索引类型吗？我完全不知道如何提高性能。
编辑：
这是 SQL 开发人员的 SQL 调优顾问显示的内容（执行计划） 此查询的 sql 没有AND c.CL_COUNTRY = 'SPAIN'
GENERAL INFORMATION SECTION
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Tuning Task Name : staName9168
Tuning Task Owner : USER
Tuning Task ID : 12125
Scope : COMPREHENSIVE
Time Limit(seconds): 1800
Completion Status : COMPLETED
Started at : 04/23/2013 15:44:35
Completed at : 04/23/2013 15:44:36
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There are no recommendations to improve the statement.
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EXPLAIN PLANS SECTION
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1- Original
-----------
Plan hash value: 3808155432
------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 21 | 54011 (1)| 00:10:49 | | | |
| 1 | SORT AGGREGATE | | 1 | 21 | | | | | |
| 2 | PX COORDINATOR | | | | | | | | |
| 3 | PX SEND QC (RANDOM) | :TQ10001 | 1 | 21 | | | Q1,01 | P->S | QC (RAND) |
| 4 | SORT AGGREGATE | | 1 | 21 | | | Q1,01 | PCWP | |
|* 5 | HASH JOIN | | 475K| 9745K| 54011 (1)| 00:10:49 | Q1,01 | PCWP | |
| 6 | BUFFER SORT | | | | | | Q1,01 | PCWC | |
| 7 | PX RECEIVE | | 475K| 6497K| 32813 (1)| 00:06:34 | Q1,01 | PCWP | |
| 8 | PX SEND BROADCAST | :TQ10000 | 475K| 6497K| 32813 (1)| 00:06:34 | | S->P | BROADCAST |
|* 9 | TABLE ACCESS BY INDEX ROWID| VEHICULE | 475K| 6497K| 32813 (1)| 00:06:34 | | | |
|* 10 | INDEX RANGE SCAN | VEHICULE_INDEX_BRAND | 616K| | 1621 (2)| 00:00:20 | | | |
| 11 | PX BLOCK ITERATOR | | 20M| 138M| 21146 (1)| 00:04:14 | Q1,01 | PCWC | |
| 12 | TABLE ACCESS FULL | CLIENT | 20M| 138M| 21146 (1)| 00:04:14 | Q1,01 | PCWP | |
------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$58A6D7F6
9 - SEL$58A6D7F6 / VEHICULE@SEL$1
10 - SEL$58A6D7F6 / VEHICULE@SEL$1
12 - SEL$58A6D7F6 / CLIENT@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
5 - access("VE_CL_ID"="CL_ID")
9 - filter("VE_CL_ID" IS NOT NULL)
10 - access("VEHICULE"."VE_BRAND"='MITSUBISHI')
Column Projection Information (identified by operation id):
-----------------------------------------------------------
1 - (#keys=0) COUNT()[22]
2 - SYS_OP_MSR()[10]
3 - (#keys=0) SYS_OP_MSR()[10]
4 - (#keys=0) SYS_OP_MSR()[10]
5 - (#keys=1)
6 - (#keys=0) "VE_CL_ID"[NUMBER,22]
7 - "VE_CL_ID"[NUMBER,22]
8 - (#keys=0) "VE_CL_ID"[NUMBER,22]
9 - "VE_CL_ID"[NUMBER,22]
10 - "VEHICULE".ROWID[ROWID,10]
11 - "CL_ID"[NUMBER,22]
12 - "CL_ID"[NUMBER,22]
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