Re: Selecting newly added column returns empty but only when selecting with other columns in table

From: Melvin Davidson <melvin6925(at)gmail(dot)com>
To: mrtruji <mrtruji(at)gmail(dot)com>
Cc: "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
Subject: Re: Selecting newly added column returns empty but only when selecting with other columns in table
Date: 2015-11-27 02:19:28
Message-ID: CANu8FixZDsz5HSPEj3iWUkUOKmr3b=yUR0oKS1+Z_62fvcy0qw@mail.gmail.com
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OK, thanks for clarifying, but just for sanity sake, it would REALLY be
nice if you would advise us of the exact version of PostgreSQL and the O/S
you are working with.

A copy of the table structure would also be helpful.

Just one more thing, is it possible you have an index on that table that
might be corrupted?

What does the following query return?

SELECT n.nspname,
i.relname,
i.indexrelname,
CASE WHEN idx.indisprimary
THEN 'pkey'
WHEN idx.indisunique
THEN 'uidx'
ELSE 'idx'
END AS type,
'INVALID'
FROM pg_stat_all_indexes i
JOIN pg_class c ON (c.oid = i.relid)
JOIN pg_namespace n ON (n.oid = c.relnamespace)
JOIN pg_index idx ON (idx.indexrelid = i.indexrelid )
WHERE idx.indisvalid = FALSE
AND i.relname = 'data'
ORDER BY 1, 2,3;

On Thu, Nov 26, 2015 at 9:10 PM, mrtruji <mrtruji(at)gmail(dot)com> wrote:

> Hi,
>
> Thanks for the reply. The limit is just to simplify results for the
> examples. The same behavior occurs when each of the three queries are not
> limited. Whenever I try to filter by the original columns and select the
> new column the resultant values for the new column are empty. Conversely,
> whenever I select the new column along with original columns without any
> filtering the resultant values for the original columns return empty. It's
> as if the added column is disconnected to the table in some way causing
> problems with queries that combine original columns and the new one.
>
> I created and filled in the new column externally using psycopg2 in Python
> so I'm not sure if that could be the source of the problem...
>
> On Thu, Nov 26, 2015 at 5:39 PM, Melvin Davidson <melvin6925(at)gmail(dot)com>
> wrote:
>
>> Is it possible you have more than one row where state = 'CA'? Putting a
>> LIMIT 1 would then restrict to only 1 row.
>> Have you tried with no limit? IE: SELECT new_col FROM data;
>>
>>
>> On Thu, Nov 26, 2015 at 7:13 PM, mrtruji <mrtruji(at)gmail(dot)com> wrote:
>>
>>> Just added a new bytea type column to an existing psql table and
>>> populated the column entirely with row data. Running into some strange
>>> query results:
>>>
>>> When I select the newly added column by itself I get all the data as
>>> expected:
>>>
>>> SELECT new_col FROM data LIMIT 1;
>>> Result: \x8481e7dec3650040b....
>>>
>>> When I try to filter with 'where' on another column in the table, I get
>>> the values from the other columns as expected but empty from my new_column:
>>>
>>> SELECT id, state, new_col FROM data WHERE state='CA' limit 1;
>>> Result: 123456_1; CA; EMPTY ROW
>>>
>>> The reverse is also true. If I select my new column in combination with
>>> other columns with no 'where' I get the correct value from my new column
>>> but empty for the other columns:
>>>
>>> SELECT id, state, new_col FROM data limit 1;
>>> Result: EMPTY ROW; EMPTY ROW; \x8481e7dec3650040b....
>>>
>>> Thanks to anyone with advice!
>>>
>>
>>
>>
>> --
>> *Melvin Davidson*
>> I reserve the right to fantasize. Whether or not you
>> wish to share my fantasy is entirely up to you.
>>
>
>

--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.

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