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【TiDB 版本】:master
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【问题描述】: 对主键 order by asc, desc 有什么区别? select * from xxx_tab where batch_no = ‘xxxx’ and fee_status = 8 order by id asc; 耗时102s。 select * from xxx_tab where batch_no = ‘xxxx’ and fee_status = 8 order by id desc; 耗时 1s。
使用explain
+------------------+-----------+------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| id | count | task | operator info |
+------------------+-----------+------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| Sort_5 | 381710.63 | root | xxx.xxx_tab.id:asc |
| └─IndexLookUp_13 | 381710.63 | root | |
| ├─IndexScan_11 | 381710.63 | cop | table:xxx_tab, index:batch_no, fee_status, range:["xxx" 8,"xxx" 8], keep order:false |
| └─TableScan_12 | 381710.63 | cop | table:xxx_tab, keep order:false |
+------------------+-----------+------+---------------------------------------------------------------------------------------------------------------------------------------------------+
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