pingcap/tidb

unix_timestamp return worng result when input with fractional digits

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#6,981 创建于 2018年7月4日

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component/expressionhelp wantedpriority/P4type/compatibility

描述

  1. What did you do? If possible, provide a recipe for reproducing the error.
mysql -P3306 -h127.0.0.1 -uroot -proot --column-type-info test;

mysql> select unix_timestamp('2011:01:01.001');
  1. What did you expect to see?
Field   1:  `unix_timestamp('2011:01:01.001')`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       LONGLONG
Collation:  binary (63)
Length:     11
Max_length: 10
Decimals:   0
Flags:      NOT_NULL BINARY NUM 

+----------------------------------+
| unix_timestamp('2011:01:01.001') |
+----------------------------------+
|                       1293814800 |
+----------------------------------+
1 row in set (0.00 sec)
  1. What did you see instead?
Field   1:  `unix_timestamp('2011:01:01.001')`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       NEWDECIMAL
Collation:  binary (63)
Length:     17
Max_length: 14
Decimals:   3
Flags:      BINARY NUM 


+----------------------------------+
| unix_timestamp('2011:01:01.001') |
+----------------------------------+
|                   1293811200.000 |
+----------------------------------+
1 row in set (0.00 sec)
  1. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?
Release Version: v2.1.0-beta-11-g1f6e12cc5
Git Commit Hash: 1f6e12cc55e534bf514eef212f1091a91b8592c9
Git Branch: HEAD
UTC Build Time: 2018-07-04 06:31:26
GoVersion: go version go1.10.1 linux/amd64
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e

贡献者指南

技术栈
gosql
领域
databasebackend
议题类型
bug
难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。
3
预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。
half day
活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。
stale
清晰度议题是否清楚说明期望改动、验收标准和下一步。
mostly clear
前置要求
Basic SQLFamiliarity with datetime functions
新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。
40
研究方向
Investigate the implementation of the `unix timestamp` function in TiDB's expression evaluation, likely in `expression/time func.go` or similar. Focus on how fractional seconds in input strings are parsed and handled. Examine the code that distinguishes between integer and decimal return types. Look for any existing tests for `unix timestamp` with fractional inputs and reproduce the issue. Consider whether the fix should adjust the return type to match MySQL's behavior (LONGLONG with integer result) or ensure correct rounding.
unix_timestamp return worng result when input with fractional digits · pingcap/tidb#6981 | Good First Issue