Re: Combining metavariables and table names

On Sun, Dec 28, 2025 at 8:39 PM H <agents(at)meddatainc(dot)com> wrote:

> Running postgresql 16 on Rocky Linux 9 developing a multi-tenant
> application where tenants will be represented by individual schemes.
>
> I am using the temporal tables extension to save updated/deleted rows and
> am running into a problem. During the development I am creating tables in
> an SQL files for testing. In my example, the SQL files also create a
> versioning trigger for the example table test using test_history to store
> updated/deleted rows using the following statements:
>
> Metavariable to store schema:
>
> \set s t
>
> ...
>
> CREATE OR REPLACE TRIGGER versioning_trigger
> BEFORE INSERT OR DELETE OR UPDATE
> ON :s.test
> FOR EACH ROW
> EXECUTE PROCEDURE public.versioning('sys_period', ':s.test_history',
> 'true');
>
> Creating the tables works as expected, as does inserting data into them.
> However, updating/deleting rows the following generates the error message
> "ERROR: schema ":s" does not exist" even though it does exist. I have
> tried different variations of ':s.test_history' such as :"s"'.test_history"
> and a number of other variations, none of which work for the
> update/deletion of a row.
>
> The only way I have gotten it to work is to add the following statement to
> the SQL file creating tables:
>
> \set stest :s'.test_history'
>
> and then to reference it like:
>
> CREATE OR REPLACE TRIGGER versioning_trigger
> BEFORE INSERT OR DELETE OR UPDATE
> ON :s.test
> FOR EACH ROW
> EXECUTE PROCEDURE public.versioning('sys_period', :"stest", 'true')
>
> Note the placement of the colon and the use of trouble quotes.
>
> I have a feeling I might be missing how to use the combination of a
> metavariable and a table name when used in an argument to a procedure.
>
> Even though I gotten it to work, what would the correct usage be?
>

If you can't get it to work the way you want it to, there's always bash
string variable substitution. I use that extensively. The benefit is
keeping all the code in one file instead of spreading it across (possibly
multiple) .sql files in addition to the shell script.

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