bulk

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2024-08-08 08:49:06 217人阅读

Oracle有2个引擎来执行PL/SQL blocks 和 subprograms。那么在执行的时候，PL/SQL 引擎把DML 语句发送给SQL 引擎，然后由SQL 引擎执行，执行完毕后，SQL 引擎把结果集在发送给PL/SQL 引擎。

与bulk 相关的有2个语法：forall 和 bulk collect。

（1）FORALL. 将数据打包，一次性从PL/SQL 引擎发送给SQL 引擎。

（2）bulk collect: 将处理之后的结果集放到bulk collect里，然后一次性把bulk collect从SQL 引擎发送给PL/SQL 引擎。

因为bulk 减少2个引擎之间的context switches，从而提升了SQL性能，当要处理的数据量越大，使用bulk 和不使用bulk 性能区别就越明显。

一. Forall测试

1.1 delete 测试

1.1.1 使用for .. loop 循环

SYS@anqing2(rac2)> desc ta;

Name Null? Type

------------------------------------------------- ----------------------------

ID NUMBER

NAME VARCHAR2(10)

SYS@anqing2(rac2)> select count(*) fromta;

COUNT(*)

----------

999999

SYS@anqing2(rac2)> select * from tawhere rownum<5;

ID NAME

---------- ----------

1 dave

测试之前，先看下变量的声明：

TYPE IdList IS TABLE OF ta.id%TYPE;

TYPE ta_row IS TABLE OF ta%ROWTYPE INDEX BYPLS_INTEGER; --声明变量

row_id_table dbms_sql.Urowid_Table;

idl IdList;

rar ta_row;

--先定一个类型，然后声明该类型的变量，官网链接如下：

http://download.oracle.com/docs/cd/E11882_01/appdev.112/e10766/tdddg_subprograms.htm#TDDDG99950

/* Formatted on 2011/7/11 11:22:37(QP5 v5.163.1008.3004) */

DECLARE

TYPEIdList IS TABLE OF ta.id%TYPE;

idl IdList;

BEGIN

SELECT id BULK COLLECT INTO idl FROM ta WHERE ROWNUM <= 100000;

FOR i IN idl.FIRST .. idl.LAST

LOOP

DELETE FROM ta WHERE id = idl (i);

END LOOP;

END;

PL/SQL procedure successfully completed.

Elapsed: 00:00:33.59 -- 花了34秒

SYS@anqing2(rac2)> rollback;

Rollback complete.

Elapsed: 00:00:29.02 --rollback 花了29秒

1.1.2 forall

/* Formatted on 2011/7/11 11:25:59(QP5 v5.163.1008.3004) */

DECLARE

TYPEIdList IS TABLE OF ta.id%TYPE;

idl IdList;

BEGIN

SELECT id BULK COLLECT INTO idl FROM ta WHERE ROWNUM <= 100000;

FORALL i IN idl.FIRST .. idl.LAST

DELETE FROM ta WHERE id = idl(i);

END;

PL/SQL procedure successfully completed.

Elapsed: 00:00:29.45 --花了30秒，速度提升不是很多。才4秒

SYS@anqing2(rac2)> rollback;

Rollback complete.

Elapsed: 00:00:39.18

1.1.3 forall + rowid

/* Formatted on 2011/7/11 11:29:33(QP5 v5.163.1008.3004) */

DECLARE

row_id_table DBMS_SQL.Urowid_Table;

BEGIN

SELECT ROWID BULK COLLECT INTOrow_id_table FROM ta WHERE ROWNUM <= 100000;

FORALL i INrow_id_table.FIRST ..row_id_table.LAST

DELETE FROM ta WHERE ROWID =row_id_table (i);

END;

PL/SQL procedure successfully completed.

Elapsed: 00:00:29.19 --比单纯的forall 块了仅1秒

SYS@anqing2(rac2)> rollback;

Rollback complete.

Elapsed: 00:00:31.08

注意一点：

FORALL只能包含一条DML 语句，而FOR LOOP 可以包含多条

1.2 Insert

SYS@anqing2(rac2)>create table ta2 as select * from ta where 1=2;

Table created.

/* Formatted on 2011/7/11 14:31:11(QP5 v5.163.1008.3004) */

DECLARE

TYPEta_row IS TABLE OF ta%ROWTYPEINDEX BY PLS_INTEGER;

Trow ta_row;

t1 INTEGER;

t2 INTEGER;

t3 INTEGER;

BEGIN

SELECT * BULK COLLECT INTO Trow FROM ta WHERE ROWNUM <= 100000;

t1 := DBMS_UTILITY.get_time;

FOR i IN 1 .. Trow.COUNT

LOOP

INSERT INTO ta2 VALUES trow (i);

END LOOP;

t2 := DBMS_UTILITY.get_time;

FORALL i IN 1 .. Trow.COUNT

INSERT INTO ta2 VALUES trow(i);

t3 := DBMS_UTILITY.get_time;

DBMS_OUTPUT.PUT_LINE (‘ExecutionTime (secs)‘);

DBMS_OUTPUT.PUT_LINE (‘---------------------‘);

DBMS_OUTPUT.PUT_LINE (‘FORLOOP: ‘ || TO_CHAR ( (t2 - t1) / 100));

DBMS_OUTPUT.PUT_LINE (‘FORALL:‘ || TO_CHAR ( (t3 - t2) / 100));

COMMIT;

END;

--结果如下：

Execution Time (secs)

---------------------

FOR LOOP: 24.52

FORALL: 2.91 -- 使用forall性能提升很明显

PL/SQL procedure successfully completed.

二. BULK COLLECT

2.1 SELECT INTO Statement with BULK COLLECT Clause

/* Formatted on 2011/7/11 15:25:28(QP5 v5.163.1008.3004) */

DECLARE

TYPE idTabIS TABLE OF ta.id%TYPE;

TYPEnameTab IS TABLE OF ta.name%TYPE;

TYPE taSetIS TABLE OF ta%ROWTYPEINDEX BY PLS_INTEGER;

tmp_ta taSet;

tmp_id idTab;

tmp_name nameTab;

BEGIN

SELECT id, name BULK COLLECT INTOtmp_id,tmp_name FROM ta WHERE ROWNUM < 5;

SELECT id, name BULK COLLECT INTOtmp_ta FROM ta WHERE ROWNUM < 5;

FOR i INtmp_ta.FIRST ..tmp_ta.LAST

LOOP

DBMS_OUTPUT.PUT_LINE(tmp_ta(i).id || ‘: ‘ ||tmp_ta (i).name);

END LOOP;

FOR j IN 1..tmp_id.count

LOOP

DBMS_OUTPUT.PUT_LINE(tmp_id(j) || ‘--‘ ||tmp_name (j));

END LOOP;

END;

198854: dave

198855: dave

198856: dave

198857: dave

198854--dave

198855--dave

198856--dave

198857--dave

PL/SQL procedure successfully completed.

2.2 Row Limits for SELECT BULK COLLECT INTO Statements

当Select bulk collect into 返回的结果集很大时，可以使用rownum 或者sample 来限制他的大小。 sample 表示总记录数的一个百分比。

DECLARE

TYPE idList IS TABLE OF ta.id%TYPE;

tmp_id idList;

tmp_id2 idList;

BEGIN

SELECT id BULK COLLECT INTO tmp_id FROM ta WHEREROWNUM <= 50;

SELECT id BULK COLLECT INTO tmp_id2 FROM taSAMPLE (1);

--这里采样为1%

DBMS_OUTPUT.PUT_LINE (‘tmp_id count is: ‘||tmp_id.count);

DBMS_OUTPUT.PUT_LINE (‘tmp_id2 count is:‘|| tmp_id2.count);

END;

结果为：

tmp_id count is: 50

tmp_id2 count is: 11044

PL/SQL procedure successfully completed.

2.3 FETCH Statement with BULK COLLECT Clause

FETCHBULK COLLECT 可以将整个结果集返回到一个或者多个collectionvariables。

2.3.1 Bulk-Fetching into Two Nested Tables

DECLARE

TYPE nameList IS TABLE OF ta. name%TYPE;

TYPE idList IS TABLE OF ta.id%TYPE;

CURSOR c1 IS SELECT id,name FROM ta WHERE rownum<20;

TYPE RecList IS TABLE OF c1%ROWTYPE;

tmp_name NameList;

tmp_id idList;

recs RecList;

v_limit PLS_INTEGER := 2;

PROCEDURE print_results IS

BEGIN

-- Check if collections are empty:

IF tmp_name IS NULL ORtmp_name.COUNT = 0 THEN

DBMS_OUTPUT.PUT_LINE(‘Noresults!‘);

ELSE

DBMS_OUTPUT.PUT_LINE(‘Result:‘);

FOR i INtmp_name.FIRST ..tmp_name.LAST LOOP

DBMS_OUTPUT.PUT_LINE(‘ name:‘ ||tmp_name(i) || ‘: id‘ ||tmp_id(i));

END LOOP;

END IF;

END;

BEGIN

DBMS_OUTPUT.PUT_LINE (‘---Processing all results simultaneously ---‘);

OPEN c1;

FETCH c1 BULK COLLECT INTOtmp_id,tmp_name;

CLOSE c1;

print_results();

DBMS_OUTPUT.PUT_LINE (‘---Processing ‘ ||v_limit || ‘ rowsat a time ---‘);

OPEN c1;

LOOP

FETCH c1 BULK COLLECT INTO tmp_id,tmp_nameLIMITv_limit;

EXIT WHENtmp_name.COUNT = 0;

print_results();

END LOOP;

CLOSE c1;

--这种情况下，每次会处理limit的个数，知道处理完

DBMS_OUTPUT.PUT_LINE (‘---Fetching records rather than columns ---‘);

OPEN c1;

FETCH c1 BULK COLLECT INTO recs;

FOR i IN recs.FIRST .. recs.LAST

LOOP

-- Now all columns from result setcome from one record

DBMS_OUTPUT.PUT_LINE (‘ Nameis: ‘ ||recs(i).name || ‘: id‘ ||recs(i).id);

END LOOP;

END;

--- Processing all results simultaneously---

Result:

--- Processing 2 rows at a time ---

Result:

Result:

Result:

Result:

Result:

Result:

Result:

Result:

Result:

Result:

--- Fetching records rather than columns---

Name is: dave: id198854

Name is: dave: id198855

Name is: dave: id198856

Name is: dave: id198857

Name is: dave: id198858

Name is: dave: id198859

Name is: dave: id198860

Name is: dave: id198861

Name is: dave: id198862

Name is: dave: id198863

Name is: dave: id198864

Name is: dave: id198865

Name is: dave: id198866

Name is: dave: id198867

Name is: dave: id198868

Name is: dave: id198869

Name is: dave: id198870

Name is: dave: id198871

Name is: dave: id198872

PL/SQL procedure successfully completed.

2.3.2 Bulk-Fetchinginto Nested Table of Records

DECLARE

CURSOR c1 IS SELECT id, name FROM ta;

TYPE NameSet IS TABLE OF c1%ROWTYPE;

tmp_ta NameSet; -- nested table of records

TYPE cursor_var_type is REF CURSOR;

cv cursor_var_type;

BEGIN

-- Assign values to nested table ofrecords:

OPEN cv FOR

SELECT id,name FROM ta WHERE rownum<10;

FETCH cv BULK COLLECT INTO tmp_ta;

CLOSE cv;

-- Print nested table of records:

FOR i IN tmp_ta.FIRST .. tmp_ta.LAST LOOP

DBMS_OUTPUT.PUT_LINE (tmp_ta(i).id || ‘ ‘||tmp_ta (i). name);

END LOOP;

END;

结果：

198854 dave

198855 dave

198856 dave

198857 dave

198858 dave

198859 dave

198860 dave

198861 dave

198862 dave

PL/SQL procedure successfully completed.

2.4 Row Limits for FETCH BULK COLLECT Statements

在 FETCH BULK COLLECT 中使用limit 控制每个collection 的大小。如果返回集很大，就分成多个collection 来处理。这个用法在2.3节中有使用。

DECLARE

TYPE numtab IS TABLE OF NUMBER INDEX BYPLS_INTEGER;

CURSOR c1 IS SELECT id FROM ta WHERE rownum<10;

empids numtab;

BEGIN

OPEN c1;

LOOP -- Fetch 10 rows or fewer in eachiteration

FETCH c1 BULK COLLECT INTO empids LIMIT 2;

EXIT WHEN empids.COUNT =0; -- Not: EXIT WHEN c1%NOTFOUND

DBMS_OUTPUT.PUT_LINE (‘------- Results fromOne Bulk Fetch --------‘);

FOR i IN 1..empids.COUNT LOOP

DBMS_OUTPUT.PUT_LINE (‘Employee Id: ‘ ||empids(i));

END LOOP;

CLOSE c1;

END;

结果如下：

------- Results from One Bulk Fetch--------

Employee Id: 198854

Employee Id: 198855

------- Results from One Bulk Fetch--------

Employee Id: 198856

Employee Id: 198857

------- Results from One Bulk Fetch--------

Employee Id: 198858

Employee Id: 198859

------- Results from One Bulk Fetch--------

Employee Id: 198860

Employee Id: 198861

------- Results from One Bulk Fetch--------

Employee Id: 198862

PL/SQL procedure successfully completed.

2.5 RETURNING INTO Clause with BULK COLLECT Clause

RETURNINGBULK COLLECT INTO 可以显示 INSERT, UPDATE, DELETE, or EXECUTE IMMEDIATE 的具体数据.

DECLARE

TYPE idList IS TABLE OF ta.id %TYPE;

tmp_id idList;

TYPE NameList IS TABLE OF ta.name%TYPE;

tmp_name NameList;

BEGIN

DELETE FROM ta WHERE rownum<10

RETURNING id,name BULK COLLECT INTOtmp_id,tmp_name;

DBMS_OUTPUT.PUT_LINE (‘Deleted ‘ ||SQL%ROWCOUNT || ‘ rows:‘);

FOR i IN tmp_id.FIRST.. tmp_id.LAST

LOOP

DBMS_OUTPUT.PUT_LINE (‘ID #‘ || tmp_id(i)|| ‘: ‘ || tmp_name(i));

END LOOP;

END;

返回结果：

Deleted 9 rows:

ID #198854: dave

ID #198855: dave

ID #198856: dave

ID #198857: dave

ID #198858: dave

ID #198859: dave

ID #198860: dave

ID #198861: dave

ID #198862: dave

PL/SQL procedure successfully completed.

2.6 Using FORALL Statement and BULK COLLECT Clause Together

2.6.1 示例1

DECLARE

TYPE idList IS TABLE OF ta.id%TYPE;

TYPE nameList IS TABLE OF ta.name%TYPE;

tmp_id idList;

tmp_id2 idList;

tmp_name nameList;

TYPE cursor_var_type is REF CURSOR;

cv cursor_var_type;

BEGIN

OPEN cv FOR SELECT id FROM ta WHERE rownum<10;

FETCH cv BULK COLLECT INTOtmp_id2;

CLOSE cv;

FORALL i IN 1..tmp_id2.count

DELETE FROM ta WHERE id=tmp_id2(i) RETURNING id,name BULK COLLECT INTOtmp_id,tmp_name;

DBMS_OUTPUT.PUT_LINE (‘Deleted‘ || SQL%ROWCOUNT || ‘ rows:‘);

FOR i INtmp_id.FIRST ..tmp_id.LAST

LOOP

DBMS_OUTPUT.PUT_LINE (‘Id #‘ ||tmp_id (i) || ‘ Name#‘ ||tmp_name (i));

END LOOP;

END;

Deleted 27 rows:

Id #198863 Name #dave

Id #198864 Name #dave

...

Id #198871 Name #dave

PL/SQL procedure successfully completed.

三. 用bulk 进行大表update 的测试

在blog：

Oracle 利用 rowid 提升 update 性能

http://blog.csdn.net/tianlesoftware/article/details/6576156

用rowid 进行了性能提示，这里测试下，看看使用bulk，性能能提升多少。在这里我们使用forall+bulk collect+ rowid 进行测试。

SQL> select count(*) from dba;

COUNT(*)

----------

3080070

SQL> select count(*) from dave;

COUNT(*)

----------

3080070

两张表都是300w。在使用rowid 时，全表更新用了近5分钟。

/* Formatted on 2011/7/11 23:19:03(QP5 v5.163.1008.3004) */

DECLARE

maxrows NUMBER DEFAULT 45000;

row_id_table DBMS_SQL.Urowid_Table;

TYPE acList IS TABLE OF dba.area_code%TYPE;

tmp_ac acList;

CURSOR c1 IS

SELECT a.area_code, b.ROWID row_id FROM dave a, dba b

WHERE a.id = b.id ORDER BY b.ROWID;

BEGIN

OPEN c1;

LOOP

FETCH c1 BULK COLLECT INTO tmp_ac, row_id_table LIMIT maxrows;

EXIT WHEN row_id_table.COUNT = 0;

FORALL i IN 1 .. row_id_table.COUNT

UPDATE dba SET prov_code = tmp_ac(i) WHERE ROWID = row_id_table(i);

COMMIT;

END LOOP;

CLOSE c1;

END;

用limit 为1000 测试，用了Elapsed: 00:06:37.34

用limit 为40000 测试，用了Elapsed: 00:04:46.94

用limit 为45000 测试，用了Elapsed: 00:04:22.82

用limit 为50000 测试，用了Elapsed: 00:04:31.09

用limit 为50000 测试，用了Elapsed: 00:04:36.12

用limit 为100000 测试，用了Elapsed: 00:09:41.22

delete 和 insert 的相关语法和上面的类似，相关部分改成如下：

forall i in 1 .. row_id_table.count insert into tb select * from ta where rowid = row_id_table(i) ;

forall i in 1 .. row_id_table.count delete from ta where rowid = row_id_table(i) ;

转自http://blog.csdn.net/tianlesoftware/article/details/6599003

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