Subject: Postgres 12 - Generated Columns - Backup/Restore

From: Santosh Udupi <[email-masked]>
Date: Wed, 20 Jan 2021 17:32:44 -0800

My Postgres 12 database tables have generated columns. I use pg_dump to
backup the database but when I restore using pg_restore, the generated
columns are empty. How do I trigger creating the data in the generated
columns?

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From: Tom Lane <[email-masked]>
Date: Wed, 20 Jan 2021 20:35:26 -0500

> columns are empty. How do I trigger creating the data in the generated

Can you give a fleshed-out example of what you're doing?

			regards, tom lane

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From: Laurenz Albe <[email-masked]>
Date: Thu, 21 Jan 2021 13:36:14 +0100

On Wed, 2021-01-20 at 17:32 -0800, Santosh Udupi wrote:
> My Postgres 12 database tables have generated columns. I use pg_dump to backup
>  the database but when I restore using pg_restore, the generated columns are empty.
>  How do I trigger creating the data in the generated columns?

Does the expression that generates the computed column uses an
expression containing a function that is marked IMMUTABLE, but
isn't really?

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com

---

From: Santosh Udupi <[email-masked]>
Date: Thu, 21 Jan 2021 05:51:26 -0800

Hi Laurenz - Based on Tom's email earlier, I realized it was my
function that was causing the issue. I am trying to figure out where the
problem is

Here is my function:

column definition is as below:

completed_date_time timestamptz GENERATED ALWAYS AS
(task_completed_date(info->>'dd', info->>'qq', info->>'dp', info->>'ej',
info->>'dq', info->>'ek') ) stored

-- 'info' is a jsonb column in the same table
------------------------------------------
-- task_completed_date() is defined as 'immutable', but calls another
function:

;create or replace FUNCTION task_completed_date(completed_date_string text,
completed_time_string text default null,
check_in_date_string text default null, check_in_time_string text default
null,
check_out_date_string text default null, check_out_time_string text default
null)

RETURNS timestamptz as
$$
begin

if check_out_date_string is not null and length(check_out_date_string)> 0
then
return
date_convert_date_time_string_to_timestamptz(check_out_date_string,
check_out_time_string);

else

return date_convert_date_time_string_to_timestamptz(completed_date_string,
completed_time_string);

end if;

exception when others then
return null;
 END ;
$$
LANGUAGE plpgsql immutable;
-----------------------------------------------------------

-- function date_convert_date_time_string_to_timestamptz is also defined as
'immutable':

create or replace FUNCTION
date_convert_date_time_string_to_timestamptz(VARIADIC params text[])

RETURNS timestamptz as
$$
begin

 return array_to_string($1 , ' ')::timestamptz ;
exception when others then
return null;
 END ;
$$
LANGUAGE plpgsql immutable;
-----------------------------------------------------------------

On Thu, Jan 21, 2021 at 4:36 AM Laurenz Albe <[email-masked]>
wrote:

> backup