[FLINK-9559] The type of a union of CHAR columns of different lengths should be VARCHAR

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Component/s: Table SQL / API
• Labels: pull-request-available
• Assignee: Zhenghua Gao
• Reporter: Hequn Cheng
• Created: 09/Jun/18 03:50
• Updated: 10/Dec/19 11:42
• Resolved: 10/Dec/19 11:42

Description

Currently, If the case-when expression has two branches which return string literal, redundant white spaces will be appended to the short string literal. For example, for the sql: case 1 when 1 then 'a' when 2 then 'bcd' end, the return value will be 'a ' of CHAR(3) instead of 'a'.

Although, this follows the behavior in strict SQL standard mode(SQL:2003). We should get the pragmatic return type in a real scenario without blank-padded.

Happily, this problem has been fixed by CALCITE-2321, we can upgrade calcite to the next release(1.17.0) and override RelDataTypeSystem in flink to configure the return type, i.e., making shouldConvertRaggedUnionTypesToVarying() return true.

Issue Links

• links to: GitHub Pull Request #6519