oracle全表扫描166G的表只花了6分钟

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oracle全表扫描166G的表只花了6分钟

来源: 作者: 时间:2016-02-16 09:27 【

如何最大限制利用cpu?如何最快速的扫描完大表。如果大表有主键,count(*)就会走主键,oracle只需要扫描主键就能完成。假设这个表没有主键,那么count(*)的时候只能走全表扫描,
如何最大限制利用cpu?如何最快速的扫描完大表。如果大表有主键,count(*)就会走主键,oracle只需要扫描主键就能完成。
假设这个表没有主键,那么count(*)的时候只能走全表扫描,数据就非常慢。这里用full(a)强制走全表来模拟。

--找100G以上的分区表
SQL> @getsegsize_big
Enter value for tablespace_name:
Enter value for owner:
Enter value for how_big_m: 100000

OWNER           SEGMENT_NAME                             SEGMENT_TYPE            BIG_M      BIG_G TABLESPACE_NAME
--------------- ---------------------------------------- ------------------ ---------- ---------- ---------------------
SPS_PUB         TB_IM_ORDER_QUE_GZ                       TABLE PARTITION    170579.875 166.581909 DATA_INPUT_GZ
SPS_GZ          TB_OS_LOG                                TABLE                  132687 129.577148 DATA_INPUT_GZ
CRM_GZ          TB_BA_PRODUCT_HIST                       TABLE              119860.625 117.051392 DATA_INPUT_GZ

3 rows selected.


--SPS_PUB.TB_IM_ORDER_QUE_GZ有166G,我们那这个表来测试一下

--了解数据分布情况
SQL> @getsegsize_partition
Enter value for dblink:
Enter value for segment_name: TB_IM_ORDER_QUE_GZ
Enter value for owner: SPS_PUB

OWNER                SEGMENT_NAME                   PARTITION_NAME                 SEGMENT_TYPE           BIG_M BIG_G TABLESPACE_NAM
-------------------- ------------------------------ ------------------------------ -------------------- ---------- ---------- ------
SPS_PUB              TB_IM_ORDER_QUE_GZ             P10                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P9                             TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P12                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P13                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P14                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P15                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P16                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P17                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P18                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P19                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P11                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P8                             TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P7                             TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P6                             TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P44                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P43                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P42                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P41                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P28                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P29                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P30                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P31                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P32                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P33                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P34                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P35                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P36                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P37                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P38                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P39                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P40                            TABLE PARTITION      .1         .0 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P22                            TABLE PARTITION     15,424.0  15.1 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P27                            TABLE PARTITION     19,058.0  18.6 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P26                            TABLE PARTITION     20,243.0  19.8 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P21                            TABLE PARTITION     21,604.0  21.1 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P24                            TABLE PARTITION     22,288.0  21.8 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P23                            TABLE PARTITION     22,794.0  22.3 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P25                            TABLE PARTITION     23,977.0  23.4 DATA_INPUT_GZ
SPS_PUB              TB_IM_ORDER_QUE_GZ             P20                            TABLE PARTITION     25,188.0  24.6 DATA_INPUT_GZ

--数据主要集中在20-27分区中,根据分区大小分组,使每个分组的数据量都差不多,因为主机有16个cpu,我打算分成4组。
6-22
23-24
25-26
27-44

--检查执行计划,分区是否走并行
SQL> explain plan for select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p6) a;

Explained.

Elapsed: 00:00:00.32
SQL> @getplan
'general,outline,starts'

Enter value for plan type:

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------------------------------------------------------------------

Plan hash value: 2890186721

----------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation              | Name               | Rows  | Cost (%CPU)| Time     | Pstart| Pstop |    TQ  |IN-OUT| PQ Distrib |
----------------------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT       |                    |     1 |     2   (0)| 00:00:01 |       |       |        |      |            |
|   1 |  SORT AGGREGATE        |                    |     1 |            |          |       |       |        |      |            |
|   2 |   PX COORDINATOR       |                    |       |            |          |       |       |        |      |            |
|   3 |    PX SEND QC (RANDOM) | :TQ10000           |     1 |            |          |       |       |  Q1,00 | P->S | QC (RAND)  |
|   4 |     SORT AGGREGATE     |                    |     1 |            |          |       |       |  Q1,00 | PC |            |
|   5 |      PX BLOCK ITERATOR |                    |     1 |     2   (0)| 00:00:01 |     1 |     1 |  Q1,00 | PCWC |            |
|   6 |       TABLE ACCESS FULL| TB_IM_ORDER_QUE_GZ |     1 |     2   (0)| 00:00:01 |     1 |     1 |  Q1,00 | PCWP |            |
----------------------------------------------------------------------------------------------------------------------------------

--ok,走全表加并行,没问题。

--session 1:
SQL> set timing on
SQL> declare
  2  v_sql varchar2(2000);
  3  v_count number;
  4  s number:=0;
  5  begin
  6    for x in 6..22 loop
  7      v_sql:='select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p'||x||') a';
  8      p(v_sql);
  9      execute immediate v_sql into v_count;
 10      p(v_count);
 11      s:=s+v_count;
 12    end loop;
 13    p('total:'||s);
 14  end;
 15  /
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p6) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p7) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p8) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p9) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p10) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p11) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p12) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p13) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p14) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p15) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p16) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p17) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p18) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p19) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p20) a
15269912
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p21) a
14474581
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p22) a
10448829
total:40193322

PL/SQL procedure successfully completed.

Elapsed: 00:06:02.03

--session 2:
SQL> set timing on
SQL> declare
  2  v_sql varchar2(2000);
  3  v_count number;
  4  s number:=0;
  5  begin
  6    for x in 23..24 loop
  7      v_sql:='select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p'||x||') a';
  8      p(v_sql);
  9      execute immediate v_sql into v_count;
 10      p(v_count);
 11      s:=s+v_count;
 12    end loop;
 13    p('total:'||s);
 14  end;
 15  /
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p23) a
14920046
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p24) a
14747020
total:29667066

PL/SQL procedure successfully completed.

Elapsed: 00:05:17.42

--session 3:
SQL> set timing on
SQL> declare
  2  v_sql varchar2(2000);
  3  v_count number;
  4  s number:=0;
  5  begin
  6    for x in 25..26 loop
  7      v_sql:='select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p'||x||') a';
  8      p(v_sql);
  9      execute immediate v_sql into v_count;
 10      p(v_count);
 11      s:=s+v_count;
 12    end loop;
 13    p('total:'||s);
 14  end;
 15  /
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p25) a
15727771
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p26) a
12998516
total:28726287

PL/SQL procedure successfully completed.

Elapsed: 00:05:16.31

--session 4:
SQL> set timing on
SQL> declare
  2  v_sql varchar2(2000);
  3  v_count number;
  4  s number:=0;
  5  begin
  6    for x in 27..44 loop
  7      v_sql:='select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p'||x||') a';
  8      p(v_sql);
  9      execute immediate v_sql into v_count;
 10      p(v_count);
 11      s:=s+v_count;
 12    end loop;
 13    p('total:'||s);
 14  end;
 15  /
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p27) a
12529834
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p28) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p29) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p30) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p31) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p32) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p33) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p34) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p35) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p36) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p37) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p38) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p39) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p40) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p41) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p42) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p43) a
0
select /*+full(a) parallel(a,4)*/count(*) from SPS_PUB.TB_IM_ORDER_QUE_GZ  partition (p44) a
0
total:12529834

PL/SQL procedure successfully completed.

Elapsed: 00:02:31.85

--最终的数据量:

SQL> select 40193322+29667066+28726287+12529834 from dual;

40193322+29667066+28726287+12529834
-----------------------------------
                          111116509

1 row selected.

Elapsed: 00:00:00.04

--其中p是存储过程:
create or replace procedure p(v_sql in varchar2)
is
begin
  dbms_output.put_line(v_sql);
end;

--getsegsize_partition.sql
set lines 200 
set pages 200 
set long 100000000
col owner for a20
col SEGMENT_NAME for a30
col SEGMENT_TYPE for a20
col TABLESPACE_NAME for a20
set ver off
col SEGMENT_NAME for a30
col big_m for 999,999.9
col big_g for 999,999.9

 select owner,segment_name,PARTITION_NAME,
       segment_type,
       round(bytes / 1024 / 1024,1)  big_m,
       round(bytes / 1024 / 1024 / 1024,1) big_g,
       tablespace_name
  from dba_segments&dblink
 where segment_name = upper('&segment_name')
 AND OWNER=upper('&owner')
 order by big_m;

因为4个窗口是同时执行的,最长的时间只用了6分钟,166G的表只要6分钟,速度已经非常快了。总共16个cpu,16个并行,已经充分利用了cpu的资源,如果资源空闲,可以这样查,如果系统资源紧张,就不要这样查了,凡事有利有弊。
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