需要优化 Oracle SQL 查询

问题描述 投票：0回答：1

我需要优化这个 Oracle SQL 查询：

select /*+ INDEX(ex1 EXCH_RATE_BK_IDX) */
            ex1.currency_id as currency_id,
            ex1.underly_currency_id as underly_currency_id,
            ex1.type_id as type_id,
            ex1.third_id as third_id,
            ex1.market_third_id as market_third_id,
            ex1.exch_d as exch_d,
            ex1.daily_dflt_f as daily_dflt_f,
            ex1.exch_rate as exch_rate,
            ex1.external_seq_no as external_seq_no,
            ex1.creation_d as creation_d,
            ex1.creation_user_id as creation_user_id,
            ex1.last_modif_d as last_modif_d,
            ex1.last_user_id as last_user_id
            /* security_level_e = 0 */
            from exch_rate ex1
               inner join ( select max(exch_d) as max_exch_d, type_id, third_id, market_third_id
                from exch_rate
                where currency_id = '1004'
                and underly_currency_id = '2'
                and exch_d >= TO_DATE('24-12-2009 00:00:00', 'DD-MM-YYYY HH24:MI:SS') and exch_d <= TO_DATE('14-10-2012 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
                group by type_id, third_id, market_third_id
                ) ex3
           on  ex1.exch_d = ex3.max_exch_d 
            and (ex1.type_id = ex3.type_id or (ex1.type_id is NULL and ex3.type_id is NULL)) 
            and (ex1.third_id = ex3.third_id or (ex1.third_id is  NULL and ex3.third_id is NULL)) 
            and (ex1.market_third_id = ex3.market_third_id or (ex1.market_third_id is NULL and ex3.market_third_id is NULL))
           where (ex1.currency_id = '1004') and ( ex1.underly_currency_id = '2') 
           and ((ex1.exch_d >= TO_DATE('24-12-2009 00:00:00', 'DD-MM-YYYY HH24:MI:SS') and (ex1.exch_d <= TO_DATE('14-10-2012 00:00:00', 'DD-MM-YYYY HH24:MI:SS'))))
            order by exch_d desc nulls last
;

建表脚本和索引如下：

CREATE TABLE "EXCH_RATE" 
   (    "CURRENCY_ID" NUMBER(14,0) NOT NULL ENABLE, 
    "UNDERLY_CURRENCY_ID" NUMBER(14,0) NOT NULL ENABLE, 
    "TYPE_ID" NUMBER(14,0), 
    "THIRD_ID" NUMBER(14,0), 
    "MARKET_THIRD_ID" NUMBER(14,0), 
    "EXCH_D" TIMESTAMP (6) NOT NULL ENABLE, 
    "DAILY_DFLT_F" NUMBER(3,0) DEFAULT 0 NOT NULL ENABLE, 
    "EXCH_RATE" NUMBER(23,14) NOT NULL ENABLE, 
    "EXTERNAL_SEQ_NO" NUMBER(20,0), 
    "CREATION_D" TIMESTAMP (6), 
    "CREATION_USER_ID" NUMBER(14,0), 
    "LAST_MODIF_D" TIMESTAMP (6), 
    "LAST_USER_ID" NUMBER(14,0), 
     CONSTRAINT "EXCH_RATE_DAILY_DFLT_CHK" CHECK (daily_dflt_f in (0, 1)) ENABLE, 
     CONSTRAINT "FK_701001" FOREIGN KEY ("CURRENCY_ID")
      REFERENCES "D_ORA_22_1_AAAMAINDB"."CURRENCY" ("ID") ON DELETE CASCADE ENABLE, 
     CONSTRAINT "FK_701002" FOREIGN KEY ("UNDERLY_CURRENCY_ID")
      REFERENCES "D_ORA_22_1_AAAMAINDB"."CURRENCY" ("ID") ON DELETE CASCADE ENABLE, 
     CONSTRAINT "FK_701003" FOREIGN KEY ("TYPE_ID")
      REFERENCES "D_ORA_22_1_AAAMAINDB"."TYPE" ("ID") ENABLE, 
     CONSTRAINT "FK_701004" FOREIGN KEY ("THIRD_ID")
      REFERENCES "D_ORA_22_1_AAAMAINDB"."THIRD_PARTY" ("ID") ENABLE, 
     CONSTRAINT "FK_701005" FOREIGN KEY ("MARKET_THIRD_ID")
      REFERENCES "D_ORA_22_1_AAAMAINDB"."THIRD_PARTY" ("ID") ENABLE
   ) 

  CREATE UNIQUE INDEX "EXCH_RATE_BK_IDX" ON "EXCH_RATE" ("CURRENCY_ID", "EXCH_D", "UNDERLY_CURRENCY_ID", "TYPE_ID", "THIRD_ID", "MARKET_THIRD_ID")

解释计划：

Explain plan
Plan hash value: 471245728
 
-----------------------------------------------------------------------------------------------------------
| Id  | Operation                              | Name             | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                       |                  |     1 |   259 |    29   (4)| 00:00:01 |
|*  1 |  FILTER                                |                  |       |       |            |          |
|   2 |   SORT GROUP BY                        |                  |     1 |   259 |    29   (4)| 00:00:01 |
|*  3 |    HASH JOIN                           |                  |     1 |   259 |    28   (0)| 00:00:01 |
|*  4 |     INDEX RANGE SCAN                   | EXCH_RATE_BK_IDX |  2291 |   174K|    14   (0)| 00:00:01 |
|   5 |     TABLE ACCESS BY INDEX ROWID BATCHED| EXCH_RATE        |  2291 |   404K|    14   (0)| 00:00:01 |
|*  6 |      INDEX RANGE SCAN                  | EXCH_RATE_BK_IDX |     9 |       |    14   (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - filter("EX1"."EXCH_D"=MAX("EXCH_D"))
   3 - access(SYS_OP_MAP_NONNULL("EX1"."TYPE_ID")=SYS_OP_MAP_NONNULL("TYPE_ID") AND 
              SYS_OP_MAP_NONNULL("EX1"."THIRD_ID")=SYS_OP_MAP_NONNULL("THIRD_ID") AND 
              SYS_OP_MAP_NONNULL("EX1"."MARKET_THIRD_ID")=SYS_OP_MAP_NONNULL("MARKET_THIRD_ID"))
   4 - access("CURRENCY_ID"=1004 AND "EXCH_D">=TIMESTAMP' 2009-12-24 00:00:00' AND 
              "UNDERLY_CURRENCY_ID"=2 AND "EXCH_D"<=TIMESTAMP' 2012-10-14 00:00:00')
       filter("UNDERLY_CURRENCY_ID"=2)
   6 - access("EX1"."CURRENCY_ID"=1004 AND "EX1"."EXCH_D">=TIMESTAMP' 2009-12-24 00:00:00' AND 
              "EX1"."UNDERLY_CURRENCY_ID"=2 AND "EX1"."EXCH_D"<=TIMESTAMP' 2012-10-14 00:00:00')
       filter("EX1"."UNDERLY_CURRENCY_ID"=2)
 
Note
-----
   - dynamic statistics used: dynamic sampling (level=2)
sql oracle query-optimization
1个回答
0
投票

在不知道您的数据是什么样子的情况下，我们无法优化您的查询。不过，我可以提出一些观察：

  1. 不要在连接子句中使用 

    OR
    ，特别是如果它只是为了处理 
    NULL
    相等性。哈希连接与 
    NVL()
    配合使用会更好，将 
    NULL
    视为两边都可以匹配的特定值：
    and NVL(ex1.type_id,-1) = NVL(ex3.type_id,-1)
    等

  2. 如果内部查询块

    group by
    中的聚合（
    ex3
    ）确实减少了其行数，我发现通常需要强制Oracle在块内执行该聚合，而不是将其推迟到连接到表中的表之后父块。为此，请使用 
    NO_MERGE
    提示来防止视图合并：

    from exch_rate ex1
            inner join ( select /*+ NO_MERGE */ max(exch_d) as max_exch_d, type_id, third_id, market_third_id
             from exch_rate
             where currency_id = '1004'
             and underly_currency_id = '2'
             and exch_d >= TO_DATE('24-12-2009 00:00:00', 'DD-MM-YYYY HH24:MI:SS') and exch_d <= TO_DATE('14-10-2012 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
             group by type_id, third_id, market_third_id
             ) ex3

  3. 您的日期范围相当广泛（2009 年至 2012 年）。如果只有几种货币（1004 种很常见）并且表中的大部分都是过时的历史条目，那么要求如此长的时间段会使索引的使用产生问题。您可能想要删除 

    INDEX
    提示。事实上，乍一看，在不了解您的数据的情况下（因此只是做出一些可能是错误的假设），我可能会暗示全表扫描和一些并行性，因为它看起来更像是一个报告查询将处理很大一部分数据：

    select /*+ USE_HASH(ex3 ex1) FULL(ex1) PARALLEL(8) */
         ex1.currency_id as currency_id,
         ex1.underly_currency_id as underly_currency_id,
         ex1.type_id as type_id,
         ex1.third_id as third_id,
         ex1.market_third_id as market_third_id,
         ex1.exch_d as exch_d,
         ex1.daily_dflt_f as daily_dflt_f,
         ex1.exch_rate as exch_rate,
         ex1.external_seq_no as external_seq_no,
         ex1.creation_d as creation_d,
         ex1.creation_user_id as creation_user_id,
         ex1.last_modif_d as last_modif_d,
         ex1.last_user_id as last_user_id
         from exch_rate ex1
            inner join ( select /*+ NO_MERGE FULL(exch_rate) */ max(exch_d) as max_exch_d, type_id, third_id, market_third_id
             from exch_rate
             where currency_id = '1004'
             and underly_currency_id = '2'
             and exch_d >= TO_DATE('24-12-2009 00:00:00', 'DD-MM-YYYY HH24:MI:SS') and exch_d <= TO_DATE('14-10-2012 00:00:00', 'DD-MM-YYYY HH24:MI:SS')
             group by type_id, third_id, market_third_id
             ) ex3
        on  ex1.exch_d = ex3.max_exch_d 
         and NVL(ex1.type_id,-1) = NVL(ex3.type_id,-1)
         and NVL(ex1.third_id,-1) = NVL(ex3.third_id,-1)
         and NVL(ex1.market_third_id,-1) = NVL(ex3.market_third_id,-1)
        where (ex1.currency_id = '1004') and ( ex1.underly_currency_id = '2') 
        and ((ex1.exch_d >= TO_DATE('24-12-2009 00:00:00', 'DD-MM-YYYY HH24:MI:SS') and (ex1.exch_d <= TO_DATE('14-10-2012 00:00:00', 'DD-MM-YYYY HH24:MI:SS'))))
         order by exch_d desc nulls last

    ;

如果您的桌子很小并且您想要获得这一亚秒，您可能需要省略 

parallel
提示。并行性在开始时会产生一些开销，因此仅将其用于没有并行性至少需要几秒钟的查询。

当然，如果

currency_id = 1004
是稀有，那么索引仍然有价值，不应该使用这些提示。只有了解您的数据才能确定哪个更合适。

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