Re: Clarify "allow_system_table_mods"

>my previous answer did not make sense as postgresql.conf is set up by
initdb
Yeah, that kind of puzzles me too.

>-O allow_system_table_mods = on
Thanks, I'll give that a try and create a new cluster, then get back to you
afterwards.

On Mon, Apr 25, 2016 at 4:05 PM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 04/25/2016 09:30 AM, Melvin Davidson wrote:
>
>> I need clarification on allow_system_table_mods parameter
>> Per the documentation:
>> *Allows modification of the structure of system tables.* This is used by
>> initdb. This parameter can only be set at server start.
>>
>
> A millisecond after hitting enter I realized my previous answer did not
> make sense as postgresql.conf is set up by initdb. Then I found this:
>
> http://www.postgresql.org/docs/9.2/static/runtime-config-short.html
>
> -O allow_system_table_mods = on
>
> So use that option when doing initdb?
>
>
>> However, attempting to modify pg_class to add another column fails with
>> "STATUS_ACCESS_VIOLATION" as below.
>> So either only certain system catalogs may be changed, or only certain
>> types of structure changes are allowed.
>> eg: add indexes, triggers
>>
>> Windows 10
>> PostgreSQL 9.2.15, compiled by Visual C++ build 1600, 32-bit
>>
>> Current user is postgres
>> allow_system_table_mods = on
>>
>> ALTER TABLE pg_catalog.pg_class ADD COLUMN relcreated timestamp DEFAULT
>> current_timestamp;
>>
>> Fails with:
>>
>> 2016-04-25 12:08:00 EDT STATEMENT: ALTER TABLE pg_catalog.pgclass ADD
>> COLUMN relcreated timestamp DEFAULT current_timestamp;
>> 2016-04-25 12:08:14 EDT LOG: server process (PID 7760) was terminated
>> by exception 0xC0000005
>> 2016-04-25 12:08:14 EDT DETAIL: Failed process was running: ALTER TABLE
>> pg_catalog.pg_class ADD COLUMN relcreated timestamp DEFAULT
>> current_timestamp;
>> 2016-04-25 12:08:14 EDT HINT: See C include file "ntstatus.h" for a
>> description of the hexadecimal value.
>> 2016-04-25 12:08:14 EDT LOG: terminating any other active server
>> processes
>>
>> From ntstatus.h
>> *#define STATUS_ACCESS_VIOLATION ((NTSTATUS)0xC0000005L) //
>> winnt*
>>
>> --
>> *Melvin Davidson*
>> I reserve the right to fantasize. Whether or not you
>> wish to share my fantasy is entirely up to you.
>>
>
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>

>my previous answer did not make sense as postgresql.conf is set up by
initdb
Yeah, that kind of puzzles me too.

>-O allow_system_table_mods = on
Thanks, I'll give that a try and create a new cluster, then get back to you
afterwards.

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