SELECT FOR ALL ENTRIES IN 通过配置优化速度

该语法在生成 Native SQL 时会根据内表数据将 Open SQL 拆分成多条在数据库中执行,在内表数据量较大的时候会发生性能问题.

优化 FOR ALL ENTRIES 可以在全局配置参数文件;

针对单独的程序可以使用 HINT 语句 覆盖参数文件的值。

 

使用 HINT 可以强行指定 FOR ALL ENTRIES 解析使用的参数：

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SELECT *   FROM [..]   FOR ALL ENTRIES IN [..]   WHERE [..]     %_HINTS ORACLE '&prefer_in_itab_opt 1&&prefer_fix_blocking -1&'   .

通过配置参数文件可以调整 FOR ALL ENTRIES 的性能（使用 TCODE: RZ10 RZ11 可以查看和调整SAP参数）

 

1). rsdb/prefer_join

使用连接(JOIN)的方式实现 FOR ALL ENTRIES, 0 – 禁用 1 – 启用

NETWEAVER 7.0 版本 DB2 和 MS SQL Sever实现了该参数,

NETWEAVER 7.1 版本加入了对 Oracle的实现

 

2) rsdb/prefer_union_all ( rsdb/prefer_join = 1 时,该参数无效 )

rsdb/prefer_union_all = 0 时, 条件之间用 OR 连接

rsdb/prefer_union_all = 1 时, 条件之间用 UNION ALL 连接

 

rsdb/prefer_union_all = 0 =>

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SELECT ...    WHERE f = itab[1]-f     OR f = itab[2]-f     ...     OR f = itab[N]-f     .

rsdb/prefer_union_all = 1 =>

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SELECT ...    WHERE f = itab[1]-f  UNION ALL SELECT ... WHERE f = itab[2]-f  ....  UNION ALL SELECT ... WHERE f = itab[N]-f  .

 

Example CODE:

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SELECT * UP TO 30 ROWS   INTO TABLE lt_bkpf   FROM bkpf.   SELECT *   INTO TABLE lt_bseg   FROM bsas   FOR ALL ENTRIES IN lt_bkpf   WHERE bukrs = lt_bkpf-bukrs     AND belnr = lt_bkpf-belnr     AND gjahr = lt_bkpf-gjahr       %_HINTS ORACLE '&prefer_union_all 1&&max_blocking_factor 7&'   .

ST05 跟踪结果：

………
SQL Statement:

 

SELECT
*
FROM
“BSAS”
WHERE
“MANDT” = :A0 AND “BUKRS” = :A1 AND “BELNR” = :A2 AND “GJAHR” = :A3

UNION ALL SELECT * FROM “BSAS” WHERE “MANDT” = :A4 AND “BUKRS” = :A5 AND “BELNR” = :A6 AND “GJAHR” = :A7
UNION ALL SELECT * FROM “BSAS” WHERE “MANDT” = :A8 AND “BUKRS” = :A9 AND “BELNR” = :A10 AND “GJAHR” = :A11
UNION ALL SELECT * FROM “BSAS” WHERE “MANDT” = :A12 AND “BUKRS” = :A13 AND “BELNR” = :A14 AND “GJAHR” = :A15
UNION ALL SELECT * FROM “BSAS” WHERE “MANDT” = :A16 AND “BUKRS” = :A17 AND “BELNR” = :A18 AND “GJAHR” = :A19
UNION ALL SELECT * FROM “BSAS” WHERE “MANDT” = :A20 AND “BUKRS” = :A21 AND “BELNR” = :A22 AND “GJAHR” = :A23
UNION ALL SELECT * FROM “BSAS” WHERE “MANDT” = :A24 AND “BUKRS” = :A25 AND “BELNR” = :A26 AND “GJAHR” = :A27

 

 

3) rsdb/prefer_in_itab_opt

rsdb/prefer_in_itab_opt 该参数被设置为 1，

如果 where 条件中仅有一个字段被内表限制,则将内表的字段放到 IN 条件中。

 

SQL IN 条件比 OR 效率高, 启用该参数可以提高效率

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SELECT ...     FOR ALL ENTRIES IN itab     WHERE f = itab-f.

会生成下面的 SQL 语句：

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SELECT ...     WHERE f     IN (itab[1]-f, itab[2]-f, ..., itab[N]-f)

 

Example1 – 启用 prefer_in_itab_opt:

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DATA: lt_bkpf TYPE TABLE OF bkpf,       lt_bseg TYPE TABLE OF bsas.   DATA: lv_bkpf TYPE i,       lv_bseg TYPE i.   SELECT * UP TO 30 ROWS   INTO TABLE lt_bkpf   FROM bkpf.   SELECT *   INTO TABLE lt_bseg   FROM bsas   FOR ALL ENTRIES IN lt_bkpf   WHERE belnr = lt_bkpf-belnr     %_HINTS ORACLE '&prefer_in_itab_opt 1&&max_blocking_factor 11&' .

ST05 跟踪结果:

…………
SQL Statement:

 

SELECT
*
FROM
“BSAS”
WHERE
“MANDT” = :A0 AND “BELNR” IN ( :A1 , :A2 , :A3 , :A4 , :A5 )

 

Example2 – 禁用prefer_in_itab_opt

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DATA: lt_bkpf TYPE TABLE OF bkpf,       lt_bseg TYPE TABLE OF bsas.   DATA: lv_bkpf TYPE i,       lv_bseg TYPE i.   SELECT *   UP TO 30 ROWS   INTO TABLE lt_bkpf   FROM bkpf.   SELECT *   INTO TABLE lt_bseg   FROM bsas   FOR ALL ENTRIES IN lt_bkpf   WHERE belnr = lt_bkpf-belnr      %_HINTS ORACLE '&prefer_in_itab_opt 0&&max_blocking_factor 11&' .

ST05 跟踪结果:

………
SQL Statement:

 

SELECT
*
FROM
“BSAS”
WHERE
“MANDT” = :A0 AND “BELNR” = :A1

OR “MANDT” = :A2 AND “BELNR” = :A3
OR “MANDT” = :A4 AND “BELNR” = :A5
OR “MANDT” = :A6 AND “BELNR” = :A7
OR “MANDT” = :A8 AND “BELNR” = :A9
OR “MANDT” = :A10 AND “BELNR” = :A11
OR “MANDT” = :A12 AND “BELNR” = :A13
OR “MANDT” = :A14 AND “BELNR” = :A15
OR “MANDT” = :A16 AND “BELNR” = :A17
OR “MANDT” = :A18 AND “BELNR” = :A19
OR “MANDT” = :A20 AND “BELNR” = :A21

 
 

4) rsdb/max_blocking_factor

该参数设定每个SQL Statement 处理的内表条件的个数。

如果内表数据为 50条, rsdb/max_blocking_factor = 5 则实际生成10条 SQL Statement,每个 SQL Statement 包含5组条件。

Example:

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DATA: lt_bkpf TYPE TABLE OF bkpf,       lt_bseg TYPE TABLE OF bsas.   DATA: lv_bkpf TYPE i,       lv_bseg TYPE i.   SELECT *    UP TO 30 ROWS    INTO TABLE lt_bkpf    FROM bkpf.   SELECT *    INTO TABLE lt_bseg    FROM bsas    FOR ALL ENTRIES IN lt_bkpf    WHERE bukrs = lt_bkpf-bukrs     AND belnr = lt_bkpf-belnr     AND gjahr = lt_bkpf-gjahr       %_HINTS ORACLE '&max_blocking_factor 7&' .

ST05 跟踪结果:

……..
SQL Statement:

 

SELECT
*
FROM
“BSAS”
WHERE
“MANDT” = :A0 AND “BUKRS” = :A1 AND “BELNR” = :A2 AND “GJAHR” = :A3 OR
“MANDT” = :A4 AND “BUKRS” = :A5 AND “BELNR” = :A6 AND “GJAHR” = :A7 OR
“MANDT” = :A8 AND “BUKRS” = :A9 AND “BELNR” = :A10 AND “GJAHR” = :A11 OR
“MANDT” = :A12 AND “BUKRS” = :A13 AND “BELNR” = :A14 AND “GJAHR” = :A15 OR
“MANDT” = :A16 AND “BUKRS” = :A17 AND “BELNR” = :A18 AND “GJAHR” = :A19 OR
“MANDT” = :A20 AND “BUKRS” = :A21 AND “BELNR” = :A22 AND “GJAHR” = :A23 OR
“MANDT” = :A24 AND “BUKRS” = :A25 AND “BELNR” = :A26 AND “GJAHR” = :A27

 
 

5). rsdb/max_in_blocking_factor

同 rsdb/max_blocking_factor 类似, 该参数针对 rsdb/prefer_in_itab_opt ,即 WHERE 条件为 IN 的情况。

 

6). rsdb/min_blocking_factor

rsdb/prefer_fix_blocking = 1 时, 该参数生效。

 

7). rsdb/min_in_blocking_factor

同 rsdb/min_blocking_factor 类似, 该参数针对 rsdb/prefer_in_itab_opt,即 WHERE 条件为 IN 的情况,

 
 

8). rsdb/prefer_fix_blocking

该参数配合 rsdb/min_blocking_factor 使用, 内表中数据的条数不能被 rsdb/max_blocking_factor 整除时，

剩余数据是否均匀的生成 SQL Statment 由该参数控制。

 

假设内表数据为20条, rsdb/max_blocking_factor=11 , rsdb/min_blocking_factor=5

当 rsdb/prefer_fix_blocking = 0 时, 会生成 2 条SQL语句，第一条条件为10个，第二条为9个.

当 rsdb/prefer_fix_blocking = 1 时, 会生成 3 条SQL语句，第一条条件为10个，第二条和第三条为5个

 

 

Oracle在解析 SQL 时可以使用替换变量,相同的 SQL 在执行时,不需要重新解析,可以提高性能,设置该参数可以保证 SQL Statement 相同。

rsdb/prefer_fix_blocking 和 rsdb/min_in_blocking_factor 针对少量数据；

合理设置可有效利用 Oracle 的替代变量,在使用 HINT 优化大量数据时指定这两个参数的意义不大。

rsdb/max_blocking_factor 设置的过大可能会使 SQL 超长,造成程序 DUMP,故参数文件中应谨慎设置；

在 HINT 中 rsdb/max_blocking_factor 可以设置的大些,但要注意需测试出合理的值,提高性能的同时避免程序DUMP,

实际使用中 ECC5 SQL Statement中最多包含320组条件,即使 max_blocking_factor 设置为1000，

实际仍按320处簇表无法利用 max_blocking_factor参数提高性能,在 ECC5测试,取BSEG每次仅处理一条数据

 

See Also

SAP NOTE 48230

 

 

ABAP Performance, SAP ABAP \ FOR ALL ENTRIES IN, SAP ABAP