Re: Improvements in psql hooks for variables

"Daniel Verite" <daniel@manitou-mail.org> writes:
> 	Tom Lane wrote:
>> One possible compromise that would address your concern about display
>> is to modify the hook API some more so that variable hooks could actually
>> substitute new values.  Then for example the bool-variable hooks could
>> effectively replace "\set AUTOCOMMIT" by "\set AUTOCOMMIT on" and
>> "\unset AUTOCOMMIT" by "\set AUTOCOMMIT off", ensuring that interrogation
>> of their values always produces sane results.

> Agreed, that looks like a good compromise.

Attached is a draft patch for that.  I chose to make a second hook rather
than complicate the assign hook API, mainly because it allows more code
sharing --- all the bool vars can share the same substitute hook, and
so can the three-way vars as long as "on" and "off" are the appropriate
substitutes.

I only touched the behavior for bool vars here, but if people like this
solution it could be fleshed out to apply to all the built-in variables.

Maybe we should merge SetVariableSubstituteHook and SetVariableAssignHook
into one function?

			regards, tom lane