执行 FORALL .. INSERT INTO .. VALUES 时的执行时间不同

Question

FORALL .. INSERT INTO .. VALUES 语句的执行时间不同。我们创建了一个模拟行为的测试。运行下面的脚本显示随机分布的 0.5 到 7-8 秒之间的执行时间。

脚本在运行 SQL Developer 的客户端上执行，并且 Oracle DB 在同一网络上的 HyperV Server VM 上运行。在此 VM 上，分配的内存和硬盘大小看起来足够了。

不同的执行时间可能是什么原因，我们有什么办法可以稳定（当然还有最小化）执行时间？

编辑：相关性能仅是 FORALL .. INSERT 语句需要的时间 - 使用 DBMS.PUT_LINE 命令在脚本中明确测量。创建测试数据的性能与我的问题无关！

这是测试脚本：

DECLARE
  SUBTYPE t_logmsg_rec IS logmsg%ROWTYPE;
  TYPE t_logmsg_list IS TABLE OF t_logmsg_rec;
  l_logmsg_list t_logmsg_list := t_logmsg_list();
  l_logmsg_rec t_logmsg_rec;
  l_max_logmsg_key_id logmsg.KEY_ID%TYPE;
BEGIN
  SELECT NVL(MAX(KEY_ID),1)
    INTO l_max_logmsg_key_id
    FROM logmsg;

  FOR i IN 1..10000 LOOP
    l_max_logmsg_key_id := l_max_logmsg_key_id + 1;
    l_logmsg_rec.key_id        := l_max_logmsg_key_id;
    l_logmsg_rec.msg_id        := 1;
    l_logmsg_rec.session_id    := 666;
    l_logmsg_rec.log_timestamp := current_timestamp;
    l_logmsg_rec.log_pck       := 'perf_test';
    l_logmsg_rec.log_user      := 'fl';
    l_logmsg_rec.log_type      := 1;
    l_logmsg_rec.log_msg       := 'test msg ' ||i;

    l_logmsg_rec.log_apl       := 1;

    l_logmsg_list.EXTEND;
    l_logmsg_list(l_logmsg_list.COUNT) := l_logmsg_rec;
  END LOOP;

  dbms_output.put_line('Start: ' || current_timestamp);

  FORALL l_idx IN 1 .. l_logmsg_list.COUNT
      INSERT INTO logmsg VALUES l_logmsg_list (l_idx);

  dbms_output.put_line('End: ' || current_timestamp);
END;
/

还有建表脚本：

CREATE TABLE "SCOTT"."LOGMSG" 
(   "KEY_ID" NUMBER(38,0) NOT NULL ENABLE, 
"MSG_ID" NUMBER(38,0) NOT NULL ENABLE, 
"LOG_TYPE" NUMBER(3,0) NOT NULL ENABLE, 
"LOG_TIMESTAMP" TIMESTAMP (6) NOT NULL ENABLE, 
"LOG_USER" VARCHAR2(32 BYTE) NOT NULL ENABLE, 
"LOG_MSG" VARCHAR2(2000 BYTE), 
"LOG_APL" NUMBER(5,0), 
"LOG_ATT" "SYS"."XMLTYPE" , 
"LOG_PCK" VARCHAR2(100 BYTE), 
"SESSION_ID" NUMBER(38,0), 
 CONSTRAINT "PK_LOGMSG" PRIMARY KEY ("KEY_ID")
USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS 
STORAGE(INITIAL 81920 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "SCOTT_I_TABLESPACE"  ENABLE
) SEGMENT CREATION IMMEDIATE 
PCTFREE 0 PCTUSED 40 INITRANS 1 MAXTRANS 255 
NOCOMPRESS LOGGING
STORAGE(INITIAL 81920 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "SCOTT_TABLESPACE" 
XMLTYPE COLUMN "LOG_ATT" STORE AS BASICFILE CLOB (
TABLESPACE "SCOTT_TABLESPACE" DISABLE STORAGE IN ROW CHUNK 16384 RETENTION 
NOCACHE LOGGING 
STORAGE(INITIAL 81920 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)) ;

CREATE INDEX "SCOTT"."IX_LOGMSG_1" ON "SCOTT"."LOGMSG" ("MSG_ID") 
PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS 
STORAGE(INITIAL 81920 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "SCOTT_I_TABLESPACE" ;

CREATE INDEX "SCOTT"."IX_LOGMSG_2" ON "SCOTT"."LOGMSG" ("SESSION_ID") 
PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS 
STORAGE(INITIAL 81920 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "SCOTT_I_TABLESPACE" ;

CREATE INDEX "SCOTT"."IX_LOGMSG_3" ON "SCOTT"."LOGMSG" ("LOG_TIMESTAMP") 
PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS 
STORAGE(INITIAL 81920 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "SCOTT_I_TABLESPACE" ;

CREATE INDEX "SCOTT"."IX_LOGMSG_C1" ON "SCOTT"."LOGMSG" ("LOG_MSG") 
PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS 
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "SCOTT_I_TABLESPACE" ;

CREATE INDEX "SCOTT"."IX_LOGMSG_C2" ON "SCOTT"."LOGMSG" ("LOG_PCK") 
PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS 
STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1
BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
TABLESPACE "SCOTT_I_TABLESPACE" ;

Answer 1

也许您可以尝试一种替代方法，以避免在数组中逐行填充。我试图用单个批量收集操作来说明相同的示例。希望对您有所帮助。

set sqlbl on;
DECLARE
  TYPE t_logmsg_tab IS TABLE OF log_msg%ROWTYPE;
  lv_log_msg t_logmsg_tab;
BEGIN


--Since i can see only 10000 values are fetched so here we need not to use LIMIT clause but if
--date volume is more then we need to put LIMIT clause to prevent memory overflow

  SELECT NVL(MAX(KEY_ID) OVER(ORDER BY 1),1)+LEVEL,
         '1'  msg_id,
         '666' session_id,
         current_timestamp,
         'perf_test' log_pck,
         'f1' log_user,
         1 log_type,
         'test msg '||LEVEL,
         '1' log_apl
         BULK COLLECT INTO 
         lv_log_msg
        FROM l_max_logmsg_key_id
        CONNECT BY LEVEL < 10001;

--Not required going for row by row processing will definitely take toll
--So avoiding and performing a bulk Collect Operation


--  SELECT NVL(MAX(KEY_ID),1)
--    INTO l_max_logmsg_key_id
--    FROM logmsg;
--
--  FOR i IN 1..10000 LOOP
--    l_max_logmsg_key_id := l_max_logmsg_key_id + 1;
--    l_logmsg_rec.key_id        := l_max_logmsg_key_id;
--    l_logmsg_rec.msg_id        := 1;
--    l_logmsg_rec.session_id    := 666;
--    l_logmsg_rec.log_timestamp := current_timestamp;
--    l_logmsg_rec.log_pck       := 'perf_test';
--    l_logmsg_rec.log_user      := 'fl';
--    l_logmsg_rec.log_type      := 1;
--    l_logmsg_rec.log_msg       := 'test msg ' ||i;
--
--    l_logmsg_rec.log_apl       := 1;
--
--    l_logmsg_list.EXTEND;
--    l_logmsg_list(l_logmsg_list.COUNT) := l_logmsg_rec;
--  END LOOP;

  IF lv_log_msg.EXISTS(1) THEN

  dbms_output.put_line('Start: ' || current_timestamp);

  FORALL l_idx IN lv_log_msg.FIRST .. lv_log_msg.LAST
      INSERT INTO logmsg VALUES lv_log_msg (l_idx);

  dbms_output.put_line('End: ' || current_timestamp);

  END IF;

END;
/