Thanks. This is helpful. Below is the result when I add a column to public.accounts.
obj.classid, -- 1259
obj.objid, -- 16409
obj.objsubid, -- 0
obj.command_tag, -- ALTER TABLE
obj.object_type, -- table
obj.schema_name, -- public
obj.object_identity, -- public.accounts
obj.in_extension; -- f
The info useful for me is command_tag, object_type, object_identity.
classid, objid is not useful since object_identity is more explicit.
objsubid is not useful because I don't need comment information for schema change.
Besides table name, I still need:
* which columns are added and their types.
* which columns have type change, the old and new types.
* which columns are dropped.
Will command field provide this info? I don't have an example and decoding it needs C code. If I cannot get such info from pg_event_trigger_ddl_commands, I may need to maintain schema snapshots myself and diff the old and new snapshots upon an alter table/view event. Which way should I go? Thanks a lot.
On Tue, May 30, 2023 at 2:42 PM Erik Wienhold <ewie@xxxxxxxxx> wrote:
> On 30/05/2023 22:23 CEST Lian Jiang <jiangok2006@xxxxxxxxx> wrote:
>
> I plan to create an event trigger to detect schema change (e.g. add/remove
> a column, change column type), and write it into a separate table (e.g.
> EVENTS). Then a process periodically reads this table to send schema change
> notification. However, the event trigger (https://www.postgresql.org/docs/current/plpgsql-trigger.html)
> (43.10.2. Triggers on Events) does not provide me info such as which table
> is altered, old and new schema. Am I missing something? Thanks very much for
> any hints.
You must use ddl_command_end event triggers[0] and call function
pg_event_trigger_ddl_commands[1] to get info such as altered table and column.
[0] https://www.postgresql.org/docs/current/event-trigger-definition.html
[1] https://www.postgresql.org/docs/current/functions-event-triggers.html
--
Erik
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