How to extract information from pg_ddl_command type

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How to extract information from pg_ddl_command type

Thomas Kellerer
The function pg_event_trigger_ddl_commands() returns several columns, one of them being "command" that is of the type "pg_ddl_command".

The manual[1] describes this column as:

> A complete representation of the command, in internal format.
> This cannot be output directly, but it can be passed to other
> functions to obtain different pieces of information about the
> command.

However, I can not find any of those "other functions" to extract information from that column.

My goal is to get the complete SQL text that fired the event trigger - is that even possible through pg_event_trigger_ddl_commands()?

Thanks
Thomas

[1] https://www.postgresql.org/docs/current/functions-event-triggers.html



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Re: How to extract information from pg_ddl_command type

Alvaro Herrera-9
On 2019-Jul-11, Thomas Kellerer wrote:

> The function pg_event_trigger_ddl_commands() returns several columns, one of them being "command" that is of the type "pg_ddl_command".
>
> The manual[1] describes this column as:
>
> > A complete representation of the command, in internal format.
> > This cannot be output directly, but it can be passed to other
> > functions to obtain different pieces of information about the
> > command.
>
> However, I can not find any of those "other functions" to extract information from that column.
>
> My goal is to get the complete SQL text that fired the event trigger - is that even possible through pg_event_trigger_ddl_commands()?

You need a C function.  See the test module in
src/test/modules/test_ddl_deparse -- it contains a very simple
implementation that doesn't really do a lot, but maybe it helps.  The
real meat of the thing is in an outdated module I wrote for 9.5.  I
think the latest version of that was posted by Alexander Shulgin in 2015
here
https://postgr.es/m/CACACo5Q_UXYwF117LBhjZ3xaMPyrgqnqE=mXvRhEfjJ51aCfwQ@...
or maybe it's here
https://postgr.es/m/CACACo5QQuAV+n4Gi+YA1JF_a+QenR6SJuP8CYdPSrXKa+FHS3A@...

--
Álvaro Herrera                https://www.2ndQuadrant.com/
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