Обсуждение: Trigger Function question

> On Jul 10, 2023, at 11:20, DAVID ROTH <adaptron@comcast.net> wrote:
>
> In a trigger function, is there a way to get a list of all of the columns in the triggering table?

You can get the table that the trigger fired on with TG_TABLE_SCHEMA and TG_TABLE_NAME, and then query the system
catalogsto get a list of columns. 

But can you tell us a bit more about your use-case?  You may be able to write the trigger in such a way that it doesn't
needto change behavior based on the columns. 

I want to use a single trigger function to log multiple tables and the tables have different columns.  I can get the
namesof the columns from the catalog.  But I have not been able to figure out how to get NEW.x when x is not known
untilrun time.
 


> On 07/10/2023 2:23 PM EDT Christophe Pettus <xof@thebuild.com> wrote:
> 
>  
> > On Jul 10, 2023, at 11:20, DAVID ROTH <adaptron@comcast.net> wrote:
> > 
> > In a trigger function, is there a way to get a list of all of the columns in the triggering table?
> 
> You can get the table that the trigger fired on with TG_TABLE_SCHEMA and TG_TABLE_NAME, and then query the system
catalogsto get a list of columns.
 
> 
> But can you tell us a bit more about your use-case?  You may be able to write the trigger in such a way that it
doesn'tneed to change behavior based on the columns.
 

> On Jul 10, 2023, at 11:29, DAVID ROTH <adaptron@comcast.net> wrote:
>
> I want to use a single trigger function to log multiple tables and the tables have different columns.  I can get the
namesof the columns from the catalog.  But I have not been able to figure out how to get NEW.x when x is not known
untilrun time. 

Unless you only want to log a subset of rows from each table, it's not required that you get the specific columns.
Here'san example of how to do a generic auditing trigger: 

    https://wiki.postgresql.org/wiki/Audit_trigger

If it's supported on your platform, you might also look at the pg_audit extension.

Thanks for the example. I have a test trigger now that does that but my application needs all of the columns.

> On 07/10/2023 2:31 PM EDT Christophe Pettus <xof@thebuild.com> wrote:
> 
>  
> > On Jul 10, 2023, at 11:29, DAVID ROTH <adaptron@comcast.net> wrote:
> > 
> > I want to use a single trigger function to log multiple tables and the tables have different columns.  I can get
thenames of the columns from the catalog.  But I have not been able to figure out how to get NEW.x when x is not known
untilrun time.
 
> 
> Unless you only want to log a subset of rows from each table, it's not required that you get the specific columns.
Here'san example of how to do a generic auditing trigger:
 
> 
>     https://wiki.postgresql.org/wiki/Audit_trigger
> 
> If it's supported on your platform, you might also look at the pg_audit extension.

> On Jul 10, 2023, at 11:37, DAVID ROTH <adaptron@comcast.net> wrote:
>
> Thanks for the example. I have a test trigger now that does that but my application needs all of the columns.

I'm not quite sure I understanding.  Logging NEW.* and OLD.* *does* get all the columns, without having to specific
queryto find out which columns the table that cause the trigger to fire has. 

I was hoping that NEW could be treated as a record or as an arrayy similar to pg_argv.

> On 07/10/2023 2:31 PM EDT Christophe Pettus <xof@thebuild.com> wrote:
> 
>  
> > On Jul 10, 2023, at 11:29, DAVID ROTH <adaptron@comcast.net> wrote:
> > 
> > I want to use a single trigger function to log multiple tables and the tables have different columns.  I can get
thenames of the columns from the catalog.  But I have not been able to figure out how to get NEW.x when x is not known
untilrun time.
 
> 
> Unless you only want to log a subset of rows from each table, it's not required that you get the specific columns.
Here'san example of how to do a generic auditing trigger:
 
> 
>     https://wiki.postgresql.org/wiki/Audit_trigger
> 
> If it's supported on your platform, you might also look at the pg_audit extension.

I saw your message about a "few" columns and missed the new.* notation.
Is there a way to get new.* into a jsonb column?

> On 07/10/2023 2:38 PM EDT Christophe Pettus <xof@thebuild.com> wrote:
> 
>  
> > On Jul 10, 2023, at 11:37, DAVID ROTH <adaptron@comcast.net> wrote:
> > 
> > Thanks for the example. I have a test trigger now that does that but my application needs all of the columns.
> 
> I'm not quite sure I understanding.  Logging NEW.* and OLD.* *does* get all the columns, without having to specific
queryto find out which columns the table that cause the trigger to fire has.
 

> On Jul 10, 2023, at 11:46, DAVID ROTH <adaptron@comcast.net> wrote:
>
> Is there a way to get new.* into a jsonb column?

The to_jsonb() function accepts a row type like NEW.*, and returns a JSONB object with the keys as column names.