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Message-ID: <39759897-4e11-4c3d-a7ab-f7e6a8c479aa@aklaver.com>
Date: Wed, 3 Jul 2024 07:39:03 -0700
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Subject: Re: Accommodating alternative column values
To: Rich Shepard <rshepard@appl-ecosys.com>,
 "pgsql-general@postgresql.org" <pgsql-general@postgresql.org>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <286181eb-9fdd-6680-de4-edcdc82d42a9@appl-ecosys.com>
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On 7/3/24 07:13, Rich Shepard wrote:
> On Wed, 3 Jul 2024, David G. Johnston wrote:
> 
>> Yeah, the simply cast suggested will not work. You’d have to apply an
>> expression that turns the current contents into an array. The current
>> contents are not likely to be an array literal.
> 
> David,
> 
> No, it's not now an array.
> 
> I thought that this expression would work, but it doesn't:
> bustrac=# alter table people alter column email set data type 
> varchar(64)[] using email::varchar(64)[];
> RROR:  malformed array literal: "frank@dmipx.com"
> DETAIL:  Array value must start with "{" or dimension information.
> 
> If I correctly understand the error detail I'd need to change the contents
> of that column for all 1280 rows to enclose the contents in curly braces
> before I can convert the datatype to an array. Is that correct?

An example:

create table array_conv(id integer, email varchar(64));

insert into array_conv values (1, 'adrian.klaver@aklaver.com'), (2, 
'aklaver@example.com');

select * from array_conv ;
  id |           email
----+---------------------------
   1 | adrian.klaver@aklaver.com
   2 | aklaver@example.com

alter table array_conv alter column email type varchar[] using array[email];

select * from array_conv ;
  id |            email
----+-----------------------------
   1 | {adrian.klaver@aklaver.com}
   2 | {aklaver@example.com}
> 
> Rich
> 
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com