原 Oracle视图中含有rownum导致不能走索引
👉 本文共约625个字，系统预计阅读时间或需3分钟。
现象
环境：oracle 11.2.0.4
今天客户说，一个视图查询很慢，让帮忙分析。
分析后，发现是rownum导致的视图不能走索引。
模拟
对原查询进行简化模拟：
这里modify_time列为varchar2类型，但是因为某些原因，web应用查询该字段必须使用date类型，所以我在该列上创建了函数索引：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 | DROP TABLE TB; CREATE TABLE TB(ID INT, modify_time varchar2(14)); INSERT INTO TB (id,modify_time) SELECT rownum, to_char(sysdate + rownum,'YYYYMMDDHH24MISS') from dual CONNECT BY LEVEL <= 20000; create index idx_1 on tb(to_date(modify_time,'YYYYMMDDHH24MISS')); create index idx_2 on tb(modify_time); begin DBMS_STATS.gather_table_stats('lhr', 'tb',cascade => TRUE, DEGREE=>16,no_invalidate => false); end; create or replace view vw1 as select id,modify_time,to_date(modify_time,'YYYYMMDDHH24MISS') modify_at,to_date(modify_time,'YYYYMMDDHH24miss') modify_at1 from tb ; create or replace view vw2 as select id,modify_time,to_date(modify_time,'YYYYMMDDHH24MISS') modify_at,rownum rn from tb ; -- 走索引 select * from vw1 where modify_time= '2024-03-01'; select * from vw1 where modify_at= to_date('2024-03-01','yyyy-mm-dd'); select * from vw1 where modify_at= to_date('20240301000000','syyyy-mm-dd hh24:mi:ss'); -- 不走索引（to_date函数大小写问题） select * from vw1 where modify_at1= to_date('2024-03-01','yyyy-mm-dd'); -- 不走索引（rownum问题） select * from vw2 where modify_at= to_date('2024-03-01','yyyy-mm-dd'); select * from vw2 where modify_time= '2024-03-01'; |
执行计划：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 | SYS@LHR11G> conn lhr/lhr Connected. LHR@LHR11G> set autot on LHR@LHR11G> select * from vw1 where modify_at= to_date('2024-03-01','yyyy-mm-dd'); no rows selected Execution Plan ---------------------------------------------------------- Plan hash value: 4159717772 ------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 31 | 1 (0)| 00:00:01 | | 1 | TABLE ACCESS BY INDEX ROWID| TB | 1 | 31 | 1 (0)| 00:00:01 | |* 2 | INDEX RANGE SCAN | IDX_1 | 1 | | 1 (0)| 00:00:01 | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access(TO_DATE("MODIFY_TIME",'YYYYMMDDHH24MISS')=TO_DATE(' 2024-03-01 00:00:00', 'syyyy-mm-dd hh24:mi:ss')) Note ----- - dynamic sampling used for this statement (level=2) Statistics ---------------------------------------------------------- 21 recursive calls 0 db block gets 150 consistent gets 1 physical reads 0 redo size 473 bytes sent via SQL*Net to client 512 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed LHR@LHR11G> select * from vw1 where modify_at= to_date('20240301000000','syyyy-mm-dd hh24:mi:ss'); no rows selected Execution Plan ---------------------------------------------------------- Plan hash value: 4159717772 ------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 31 | 1 (0)| 00:00:01 | | 1 | TABLE ACCESS BY INDEX ROWID| TB | 1 | 31 | 1 (0)| 00:00:01 | |* 2 | INDEX RANGE SCAN | IDX_1 | 1 | | 1 (0)| 00:00:01 | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access(TO_DATE("MODIFY_TIME",'YYYYMMDDHH24MISS')=TO_DATE('202403010000 00','syyyy-mm-dd hh24:mi:ss')) Note ----- - dynamic sampling used for this statement (level=2) Statistics ---------------------------------------------------------- 21 recursive calls 0 db block gets 150 consistent gets 0 physical reads 0 redo size 473 bytes sent via SQL*Net to client 512 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed LHR@LHR11G> select * from vw1 where modify_at1= to_date('2024-03-01','yyyy-mm-dd'); no rows selected Execution Plan ---------------------------------------------------------- Plan hash value: 2878482057 -------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 31 | 22 (0)| 00:00:01 | |* 1 | TABLE ACCESS FULL| TB | 1 | 31 | 22 (0)| 00:00:01 | -------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - filter(TO_DATE("MODIFY_TIME",'YYYYMMDDHH24miss')=TO_DATE(' 2024-03-01 00:00:00', 'syyyy-mm-dd hh24:mi:ss')) Note ----- - dynamic sampling used for this statement (level=2) Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 76 consistent gets 0 physical reads 0 redo size 473 bytes sent via SQL*Net to client 512 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed LHR@LHR11G> select * from vw2 where modify_at= to_date('2024-03-01','yyyy-mm-dd'); no rows selected Execution Plan ---------------------------------------------------------- Plan hash value: 1470101981 ---------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ---------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 19745 | 674K| 22 (0)| 00:00:01 | |* 1 | VIEW | VW2 | 19745 | 674K| 22 (0)| 00:00:01 | | 2 | COUNT | | | | | | | 3 | TABLE ACCESS FULL| TB | 19745 | 424K| 22 (0)| 00:00:01 | ---------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - filter("MODIFY_AT"=TO_DATE(' 2024-03-01 00:00:00', 'syyyy-mm-dd hh24:mi:ss')) Note ----- - dynamic sampling used for this statement (level=2) Statistics ---------------------------------------------------------- 21 recursive calls 0 db block gets 216 consistent gets 0 physical reads 0 redo size 465 bytes sent via SQL*Net to client 512 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed LHR@LHR11G> select * from vw1 where modify_time= '2024-03-01'; no rows selected Execution Plan ---------------------------------------------------------- Plan hash value: 956939525 ------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 31 | 1 (0)| 00:00:01 | | 1 | TABLE ACCESS BY INDEX ROWID| TB | 1 | 31 | 1 (0)| 00:00:01 | |* 2 | INDEX RANGE SCAN | IDX_2 | 1 | | 1 (0)| 00:00:01 | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("MODIFY_TIME"='2024-03-01') Note ----- - dynamic sampling used for this statement (level=2) Statistics ---------------------------------------------------------- 37 recursive calls 0 db block gets 81 consistent gets 0 physical reads 0 redo size 546 bytes sent via SQL*Net to client 512 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed LHR@LHR11G> select * from vw2 where modify_time= '2024-03-01'; no rows selected Execution Plan ---------------------------------------------------------- Plan hash value: 1470101981 ---------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ---------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 19745 | 848K| 22 (0)| 00:00:01 | |* 1 | VIEW | VW2 | 19745 | 848K| 22 (0)| 00:00:01 | | 2 | COUNT | | | | | | | 3 | TABLE ACCESS FULL| TB | 19745 | 597K| 22 (0)| 00:00:01 | ---------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - filter("MODIFY_TIME"='2024-03-01') Note ----- - dynamic sampling used for this statement (level=2) Statistics ---------------------------------------------------------- 21 recursive calls 0 db block gets 218 consistent gets 0 physical reads 0 redo size 538 bytes sent via SQL*Net to client 512 bytes received via SQL*Net from client 1 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 0 rows processed LHR@LHR11G> |
本人提供Oracle(OCP、OCM)、MySQL(OCP)、PostgreSQL(PGCA、PGCE、PGCM)等数据库的培训和考证业务，私聊QQ646634621或微信dbaup66，谢谢！
