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https://issues.apache.org/jira/browse/PHOENIX-4815?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16622908#comment-16622908
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Thomas D'Silva commented on PHOENIX-4815:
-----------------------------------------

[~Jaanai] Thanks for your patch. 

After PHOENIX-3534, we don't store parent table column metadata along with the 
child metadata, so you shouldn't have to propagate changes to the child views. 
Could you add more comments in MetadataEndpointImpl. modifyColum() ? What 
happens to existing data if you decrease the maxlength or scale ?

Can you create a github pull request so that it will be easier to comment and 
provide feedback inline with the code?

> support alter table modify column 
> ----------------------------------
>
>                 Key: PHOENIX-4815
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-4815
>             Project: Phoenix
>          Issue Type: Improvement
>    Affects Versions: 4.12.0
>            Reporter: Jaanai
>            Assignee: Jaanai
>            Priority: Major
>         Attachments: PHOENIX-4815.patch
>
>
> if we want to change max length or scale of  fields of  variable length type( 
>  example for :varchar, char and decimal type etc),  we can not drop column to 
> recreate new column when the table has massive data,  which may affects 
> online service,meanwhile, it is also very expensive. so sometimes this 
> function is very useful.
> Taking ORACLE dialect as an reference 
> {code:java}
> alter table
>    table_name
> modify
>    column_name  datatype;
> {code}
> reference link: 
> https://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_3001.htm#i2103956



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