[jira] [Comment Edited] (CALCITE-2321) Support ragged fixed length value union be variable

["Hequn Cheng (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-2321?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16483878#comment-16483878 ] 

Hequn Cheng edited comment on CALCITE-2321 at 5/22/18 2:23 PM:
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Hi [~julianhyde], thanks for your reply. I test Oracle/SqlServer/Mysql and they all return the value without blank-padded. Also, it seems that there is no way to turn blank-padded on. I found some clear descriptions in mysql reference manual: "If all types are character string (CHAR or VARCHAR), the result is VARCHAR with maximum length determined by the longest character length of the operands". Maybe we should make {{shouldRaggedFixedLengthValueUnionBeVariable()}} configurable meanwhile return true by default? 

As for creating a type system, other system can create their own type system by extending {{RelDataTypeSystemImpl}}, and this may not be a hard work. I tried to set it via dialect, but find it is hard to make use of it in {{SqlTypeFactoryImpl}} during sql to rel conversion. It seems that dialect is used during rel to sql conversion.

Thanks, Hequn


was (Author: hequn8128):
Hi [~julianhyde], thanks for your reply. I test Oracle/SqlServer/Mysql and they all return the value without blank-padded. Also, it seems that there is no way to turn blank-padded on. Maybe we should make {{shouldRaggedFixedLengthValueUnionBeVariable()}} configurable meanwhile return true by default? 

As for creating a type system, other system can create their own type system by extending {{RelDataTypeSystemImpl}}, and this may not be a hard work. I tried to set it via dialect, but find it is hard to make use of it in {{SqlTypeFactoryImpl}} during sql to rel conversion. It seems that dialect is used during rel to sql conversion.

Thanks, Hequn

> Support ragged fixed length value union be variable
> ---------------------------------------------------
>
>                 Key: CALCITE-2321
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2321
>             Project: Calcite
>          Issue Type: New Feature
>          Components: core
>            Reporter: Hequn Cheng
>            Assignee: Hequn Cheng
>            Priority: Major
>
> The {{shouldRaggedFixedLengthValueUnionBeVariable()}} function in {{SqlTypeFactoryImpl}} always return false now. It is good to make it configurable since some system may need the function to return true to provide pragmatic behavior. For example, for the sql: case 1 when 1 then 'a' when 2 then 'bcd' end, we need the return value to be 'a' instead of 'a  ' of CHAR(3).
> I see one option to solve this issue: Add {{boolean shouldRaggedFixedLengthValueUnionBeVariable()}} in {{RelDataTypeSystem}}, so external system can override to configure the value.
> Any suggestions are welcomed. Thanks a lot.



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