Support parameters in table function arguments

[kasiafi]

This is an improvement. It allows you to use parameters in table function scalar arguments:

PREPARE stmt1 FROM 
SELECT * FROM TABLE(postgresql.system.query(query => ?));

EXECUTE stmt1 USING 'SELECT * FROM tpch.region';

Documentation

Existing documentation is updated in this PR. Some examples (like the above) should be added to the documentation of the query pass-through table functions #12725 cc @colebow @mosabua

edit: @colebow @mosabua, I removed the second example, which included query => format('SELECT * FROM %s', ?). As @martint noticed (#12910 (comment)), it is the kind of usage we shouldn't recommend in the docs.

Release notes

# General
* Support parameters in table function arguments.

[sajjoseph]

Thanks @kasiafi for this fix. It will go a long way to make PTF query pushdown work for regular use cases.

[martint]

The second example is not something we should generally recommend. It’s a vector for potential sql injection.

[kasiafi]

The second example is not something we should generally recommend. It’s a vector for potential sql injection.

I don't think we're going to prevent such usage. Maybe we should add a warning in the docs?

[martint]

No, we’re not, but we shouldn’t provide such an example in the docs