一.前言：
一開始分區表和位圖索引怎么會掛鈎呢？可能現實就是這么的不期而遇；比如說一張表的字段是年月日—‘yyyy-mm-dd’，重復率高吧，適合建位圖索引吧，而且這張表數據量也不小，也適合轉換成分區表吧！下面我來比較一下分區表和分區字段位圖索引的性能！
二.實驗
生產上的表結構以及索引：
create table LOT_WIN_RESULT_DETAIL
(
id INTEGER not null,
rpt_date DATE,
sys_game_level_code_id INTEGER,
game_desc VARCHAR2(50),
periods_no VARCHAR2(50),
start_tt VARCHAR2(10),
end_tt VARCHAR2(10),
ok_dtt VARCHAR2(10),
ok_ind CHAR(1),
open_code VARCHAR2(500),
remark VARCHAR2(50),
json_result VARCHAR2(4000),
getdata_dtt TIMESTAMP(6),
last_modfiy_user_id INTEGER,
last_modfiy_user_name VARCHAR2(50),
last_modfiy_dtt TIMESTAMP(6),
platform_ident VARCHAR2(45)
)
tablespace NB_TBS_YOBET
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 24M
next 1M
minextents 1
maxextents unlimited
);
-- Create/Recreate indexes
create bitmap index IX1_LOT_WIN_DTL on LOT_WIN_RESULT_DETAIL (PLATFORM_IDENT) tablespace NB_INX_TBS_YOBET
;
create index IX2_LOT_WIN_DTL on LOT_WIN_RESULT_DETAIL (SYS_GAME_LEVEL_CODE_ID, PERIODS_NO) tablespace NB_INX_TBS_YOBET
;
create bitmap index IX4_LOT_WIN_DTL on LOT_WIN_RESULT_DETAIL (RPT_DATE) tablespace NB_INX_TBS_YOBET
;
create index LX_LOT_WIN_RESULT_DETAIL_TIME on LOT_WIN_RESULT_DETAIL (GETDATA_DTT) tablespace NB_INX_TBS_YOBET
;
-- Create/Recreate primary, unique and foreign key constraints
alter table LOT_WIN_RESULT_DETAIL add constraint PK_LOT_WIN_RESULT_DETAIL primary key (ID) using index tablespace NB_TBS_YOBET
;
模擬建一張一模一樣的分區表（ LOT_WIN_RESULT_DETAIL_part），以rpt_date時間字段分區，且把數據量插入過來：
create table LOT_WIN_RESULT_DETAIL_part
(
id INTEGER not null,
rpt_date DATE,
sys_game_level_code_id INTEGER,
game_desc VARCHAR2(50),
periods_no VARCHAR2(50),
start_tt VARCHAR2(10),
end_tt VARCHAR2(10),
ok_dtt VARCHAR2(10),
ok_ind CHAR(1),
open_code VARCHAR2(500),
remark VARCHAR2(50),
json_result VARCHAR2(4000),
getdata_dtt TIMESTAMP(6),
last_modfiy_user_id INTEGER,
last_modfiy_user_name VARCHAR2(50),
last_modfiy_dtt TIMESTAMP(6),
platform_ident VARCHAR2(45)
)PARTITION BY RANGE(RPT_DATE) INTERVAL (NUMTODSINTERVAL(1, 'DAY'))
(
PARTITION RPT_DATE_20191218 VALUES LESS THAN(TO_DATE('2019-12-19', 'YYYY-MM-DD'))
) tablespace NB_TBS_YOBET ;
create bitmap index IX1 on LOT_WIN_RESULT_DETAIL_part (PLATFORM_IDENT)
local tablespace NB_INX_TBS_YOBET
;
create index IX2 on LOT_WIN_RESULT_DETAIL_part (SYS_GAME_LEVEL_CODE_ID, PERIODS_NO)
local tablespace NB_INX_TBS_YOBET
;
create index LX3 on LOT_WIN_RESULT_DETAIL_part (GETDATA_DTT) lcoal tablespace NB_INX_TBS_YOBET
;
-- Create/Recreate primary, unique and foreign key constraints
alter table LOT_WIN_RESULT_DETAIL_part
add constraint PK_LOT_WIN_RESULT_DETAIL_p primary key (ID)
using index
tablespace NB_TBS_YOBET
;
insert into LOT_WIN_RESULT_DETAIL_part select * from LOT_WIN_RESULT_DETAIL;
數據庫都是89萬。
BEGIN
DBMS_STATS.GATHER_TABLE_STATS( OWNNAME => 'RACTTFC',
TABNAME => 'LOT_WIN_RESULT_DETAIL_part',
CASCADE => TRUE);
END;
/
BEGIN
DBMS_STATS.GATHER_TABLE_STATS( OWNNAME => 'RACTTFC',
TABNAME => 'LOT_WIN_RESULT_DETAIL_part',
CASCADE => TRUE);
END;
/
2.1 時間分區字段范圍查詢
語句如下：
select rpt_date,
periods_no,
open_code,
json_result,
remark,
ok_dtt as start_tt,
GAME_DESC,
rownums
from (select rpt_date,
periods_no,
a.open_code,
a.json_result,
a.remark,
a.ok_dtt,
a.GAME_DESC,
ROW_NUMBER() OVER(ORDER BY to_number(periods_no) desc) as rownums
from lot_win_result_detail a
where rpt_date >=
to_date('2019-12-23 00:00:00', 'yyyy-mm-dd HH24:mi:ss')
and rpt_date <=
to_date('2019-12-24 23:59:59', 'yyyy-mm-dd HH24:mi:ss')
and sys_game_level_code_id = 5827
and ok_ind >= '1'
and PLATFORM_IDENT = 'af') a
where rownums <= 10
order by to_number(periods_no) desc;
執行計划如下：
采用了bitmap 索引范圍掃描，CPU成本3652；
select rpt_date,
periods_no,
open_code,
json_result,
remark,
ok_dtt as start_tt,
GAME_DESC,
rownums
from (select rpt_date,
periods_no,
a.open_code,
a.json_result,
a.remark,
a.ok_dtt,
a.GAME_DESC,
ROW_NUMBER() OVER(ORDER BY to_number(periods_no) desc) as rownums
from lot_win_result_detail_part a
where rpt_date >=
to_date('2019-12-23 00:00:00', 'yyyy-mm-dd HH24:mi:ss')
and rpt_date <=
to_date('2019-12-24 23:59:59', 'yyyy-mm-dd HH24:mi:ss')
and sys_game_level_code_id = 5827
and ok_ind >= '1'
and PLATFORM_IDENT = 'af') a
where rownums <= 10
order by to_number(periods_no) desc；
基於分區過略，且基數2881比2671大，最終消耗的成本1442比3652低的多，且最開始進行的分區表索引范圍掃描成本105比非分區表的539 小的多。
2.2時間分區字段等值
select rpt_date,
periods_no,
open_code,
json_result,
remark,
ok_dtt as start_tt,
GAME_DESC,
rownums
from (select rpt_date,
periods_no,
a.open_code,
a.json_result,
a.remark,
a.ok_dtt,
a.GAME_DESC,
ROW_NUMBER() OVER(ORDER BY to_number(periods_no) desc) as rownums
from lot_win_result_detail a
where rpt_date =
to_date('2019-12-23', 'yyyy-mm-dd')
and sys_game_level_code_id = 5827
and ok_ind >= '1'
and PLATFORM_IDENT = 'af') a
where rownums <= 10
order by to_number(periods_no) desc;
單個值的查詢的時候，bitmap沒有進行范圍掃描，進行了單個等值查詢，通過索引范圍掃描，然后再通過bimap索引轉換成ROWID,最后通過又通過bitmap回表，CPU 耗費成本2515；
同理，換成分區表：
select rpt_date,
periods_no,
open_code,
json_result,
remark,
ok_dtt as start_tt,
GAME_DESC,
rownums
from (select rpt_date,
periods_no,
a.open_code,
a.json_result,
a.remark,
a.ok_dtt,
a.GAME_DESC,
ROW_NUMBER() OVER(ORDER BY to_number(periods_no) desc) as rownums
from lot_win_result_detail_part a
where rpt_date =
to_date('2019-12-23', 'yyyy-mm-dd')
and sys_game_level_code_id = 5827
and ok_ind >= '1'
and PLATFORM_IDENT = 'af') a
where rownums <= 10
order by to_number(periods_no) desc；
整個執行計划是走的單個分區，通過索引范圍掃描，然后再通過bimap索引轉換成ROWID,最后通過又通過bitmap回表，CPU 耗費成本763，遠遠小於2515，且單個的索引掃描51 遠遠小於上述的551索引范圍掃描（這個是分區表利用本地索引的優勢）；
整個兩次對比結果bitmap無論是在范圍查詢還是單個的等值查詢都是完敗。
2.3 分區表分區索引變成全局索引
drop index IX222;
create index IX222 on LOT_WIN_RESULT_DETAIL_part (SYS_GAME_LEVEL_CODE_ID, PERIODS_NO) tablespace NB_INX_TBS_YOBET;
BEGIN
DBMS_STATS.GATHER_TABLE_STATS( OWNNAME => 'RACTTFC',
TABNAME => 'LOT_WIN_RESULT_DETAIL_part',
CASCADE => TRUE);
END;
/
select rpt_date,
periods_no,
open_code,
json_result,
remark,
ok_dtt as start_tt,
GAME_DESC,
rownums
from (select rpt_date,
periods_no,
a.open_code,
a.json_result,
a.remark,
a.ok_dtt,
a.GAME_DESC,
ROW_NUMBER() OVER(ORDER BY to_number(periods_no) desc) as rownums
from lot_win_result_detail a
where rpt_date >=
to_date('2019-12-23 00:00:00', 'yyyy-mm-dd HH24:mi:ss')
and rpt_date <=
to_date('2019-12-24 23:59:59', 'yyyy-mm-dd HH24:mi:ss')
and sys_game_level_code_id = 5827
and ok_ind >= '1'
and PLATFORM_IDENT = 'af') a
where rownums <= 10
order by to_number(periods_no) desc;
分區范圍內的全表掃描，並沒有用到新建的哪個索引，CPU成本4587，遠高於bitmap的3652；
單個值的查詢：
select rpt_date,
periods_no,
open_code,
json_result,
remark,
ok_dtt as start_tt,
GAME_DESC,
rownums
from (select rpt_date,
periods_no,
a.open_code,
a.json_result,
a.remark,
a.ok_dtt,
a.GAME_DESC,
ROW_NUMBER() OVER(ORDER BY to_number(periods_no) desc) as rownums
from lot_win_result_detail_part a
where rpt_date =date'2019-12-23'
and sys_game_level_code_id = 5827
and ok_ind >= '1'
and PLATFORM_IDENT = 'af') a
where rownums <= 10
order by to_number(periods_no) desc;
同理一樣的全局索引沒有使用，2193和2515是一個數量級的，差距不是很明顯。
三.結論
綜上所述，bitmap 在進行等值與以及范圍查詢的時候，整個執行過程大致一樣，但是，主要是分區表能夠在分區范圍內利用本地索引進行掃描（全局索引幾乎是幾個量級），非分區表沒有這種優勢；
索引在rang范圍查詢字段方面。建議使用分區加local 索引，會造成BITMAP INDEX RANGE SCAN並沒有PARTITION RANGE ITERATOR 加local 索引高效,值得注意的是OLTP在線環境如果是DML比較頻繁，不會建議使用bitmap索引，可能會鎖表，引起業務hang住。