Re: BDR Alter table failing

Based on my experience, I can say BDR does not performs pre-DDL checks. For example, if you try to CREATE TABLE with the name of an existing table, BDR will acquire lock anyway, and then will fail when executing the DDL statement on the first node, because the table already exists.

In your case, it's the same: BDR does not checks(nor needs to) if the DDL statement is or not required, as that's a dba dutty. Then, BDR executes the statement(ane acquires locks), and fails because it would require a full table rewrite, which, at the time, is not supported by BDR.

A workaround for this would be:

- ALTER TABLE .... ADD COLUMN (with another name)
- UPDATE (to convert values from the old column to the new one)
- ALTER TABLE .... DROP COLUMN (on the old column)
- ALTER TABLE .... RENAME COLUMN (so new column alhas the same name)

Regards,

Alvaro Aguayo
Jefe de Operaciones
Open Comb Systems E.I.R.L.

Oficina: (+51-1) 3377813 | RPM: #034252 / (+51) 995540103  | RPC: (+51) 954183248
Website: www.ocs.pe

Sent from my Sony Xperia™ smartphone

---- Will McCormick wrote ----

But this is the exact column definition that exists on the table when I
execute the statement ....

It's like it does not check the pre-existing state of the column. Our code
is expecting a column already exists error but this error predicates that.

On Wed, Apr 27, 2016 at 10:21 AM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

> On 04/27/2016 07:13 AM, Will McCormick wrote:
>
>> Why does this not work? From what I read only default values should
>> cause issue. I'm on release 9.4.4:
>>
>>
>> bms=# ALTER TABLE trap ALTER COLUMN trap_timestamp TYPE TIMESTAMP WITH
>> TIME ZONE;
>> ERROR: ALTER TABLE ... ALTER COLUMN TYPE may only affect UNLOGGED or
>> TEMPORARY
>> tables when BDR is active; trap is a regular table
>>
>
> http://bdr-project.org/docs/stable/ddl-replication-statements.html
>
> 8.2.3. DDL statements with restrictions
>
> ALTER TABLE
>
> Generally ALTER TABLE commands are allowed. There are a however
> several sub-commands that are not supported, mainly those that perform a
> full-table re-write.
>
> ...
>
> ALTER COLUMN ... TYPE - changing a column's type is not supported. Chaning
> a column in a way that doesn't require table rewrites may be suppported at
> some point.
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com
>