pingcap/tidb

Compatible problem on `asin` with mysql

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#6,832 opened on Jun 13, 2018

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component/expressiongood first issuehelp wantedpriority/P4type/compatibility

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Description

Please answer these questions before submitting your issue. Thanks!

  1. What did you do? If possible, provide a recipe for reproducing the error.

  2. What did you expect to see?

mysql> select asin(-0.999999999);
+---------------------+
| asin(-0.999999999)  |
+---------------------+
| -1.5707516054359754 |
+---------------------+
1 row in set (0.00 sec)
  1. What did you see instead?
mysql> select asin(-0.999999999);
+--------------------+
| asin(-0.999999999) |
+--------------------+
| -1.570751605435964 |
+--------------------+
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)?

master branch commit message: 0ab1b228c0e14f4e62d9de93028183bb1df58125

Contributor guide

Research direction
Compare TiDB's asin implementation with MySQL's to find the precision difference and correct the calculation.
Tech stack
go
Domain
database
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
SQL
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40