oracle 为什么没有使用索引的一种情况

存在以下索引

SQL> SELECT INDEX_NAME,COLUMN_NAME FROM USER_IND_COLUMNS WHERE INDEX_NAME='IDX_GBDS_CLIENT_GAME_EVENT';ITPUB个人空间(n(zFsII
 
1h&\/Wx{Y#x g2d#O0INDEX_NAME                     COLUMN_NAMEITPUB个人空间2hV8Ye-?*p
------------------------------ --------------------------------------------------------------------------------
pH._:p%` e(q0IDX_GBDS_CLIENT_GAME_EVENT     CLIENT_IDITPUB个人空间$la/j-T0[ s;tQ:`
IDX_GBDS_CLIENT_GAME_EVENT     GAME_CODE_ID
+g+^e]&M~*`0IDX_GBDS_CLIENT_GAME_EVENT     EVENT_DATE
|4pU7qd"z{ j0IDX_GBDS_CLIENT_GAME_EVENT     BET_TYPE

1.下面这样写不会用上索引

SQL> select * from tb_game_bet_detail_snapshot where game_code_id=50000;

no rows selected

~WP\9?C-e0Execution PlanITPUB个人空间 Z~"du} Vy0rK;T)t
----------------------------------------------------------
aL#y2O
zT C0   0      SELECT STATEMENT ptimizer=CHOOSE (Cost=7 Card=1050 Bytes=68
R m6Jf2u;C-r0          250)

   1    0   TABLE ACCESS (FULL) OF 'TB_GAME_BET_DETAIL_SNAPSHOT' (Cost
S*Gct.@3i)U!IdZ0          =7 Card=1050 Bytes=68250)

StatisticsITPUB个人空间V$Or$fp,@/m7s,w
----------------------------------------------------------
d!K4`F6HW
x~0          0  recursive calls
-U!GQ
Z5\:z!TF0          0  db block getsITPUB个人空间n1r+y3fo7G
        126  consistent getsITPUB个人空间x)I HW m
          0  physical reads
{9US@S0          0  redo size
5G'uH/E ?8TxhB | I0        778  bytes sent via SQL*Net to client
s Ghr!n^0        364  bytes received via SQL*Net from client
U]+R0g$Q`
\f0          1  SQL*Net roundtrips to/from clientITPUB个人空间v-UP3{6z]y*B!]g~
          0  sorts (memory)ITPUB个人空间#aNw.c%UW`r!\
          0  sorts (disk)ITPUB个人空间*IV,Z~"fw)Z+jj*D
          0  rows processed

2.把谓词全部写上 用上快速索引扫描 一致性读也降下来

SQL> select client_id,game_code_id,event_date,bet_type from tb_game_bet_detail_sITPUB个人空间+h;i'Pt-W'zyM!L
napshot where game_code_id=50000;

no rows selected

ITPUB个人空间
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Execution Plan
B%\:b9X'm WL0----------------------------------------------------------
j1Y
|6k%c Fl [p _3A0   0      SELECT STATEMENT ptimizer=CHOOSE (Cost=5 Card=1050 Bytes=23
KI,_$N_s1yk0          100)

   1    0   INDEX (FAST FULL SCAN) OF 'IDX_GBDS_CLIENT_GAME_EVENT' (UN
l*Y'j
v`/\-[Q0          IQUE) (Cost=5 Card=1050 Bytes=23100)

StatisticsITPUB个人空间x.a)X yk5E[
----------------------------------------------------------
5PY.P5e-xe+Et0          0  recursive callsITPUB个人空间F*f%sU4G)JU+v6B
          0  db block getsITPUB个人空间GS8B+\5OP
p:I(V:Gz
Iu
         35  consistent getsITPUB个人空间G`"]R6Z&Go#h#g
          0  physical reads
'e+A4\:?B?u:VPj0          0  redo size
ps'}ua4l C0        353  bytes sent via SQL*Net to client
:V!^V2JV4a+v0        364  bytes received via SQL*Net from client
uLC4Y1Z*DLy0          1  SQL*Net roundtrips to/from clientITPUB个人空间P7nGSt%a3k
          0  sorts (memory)
q1PO/gV0          0  sorts (disk)
2L%?o H8`+K?R0          0  rows processed

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