Re: psql: add \pset true/false

On Thu, Dec 3, 2015 at 10:09 AM, Kyotaro HORIGUCHI
<horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Hello,
>
> At Thu, 3 Dec 2015 09:24:35 +0900, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote in <CAB7nPqTTZXaiVj0_FWvp8hPLLD_yDa8cnS4iuy_HgSOgFz09HA(at)mail(dot)gmail(dot)com>
>> On Thu, Dec 3, 2015 at 3:10 AM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
>> > On 11/15/15 7:37 PM, Peter Eisentraut wrote:
>> > I was more thinking it would be nice to be able to temporarily
>> > over-ride/wrap what an output function is doing. AFAIK that would allow this
>> > to work everywhere (row(), copy, etc). I don't know of any remotely
>> > practical way to do that, though.
>>
>> You can basically do that with a custom data type and at worse a
>> custom GUC, no? It does not seem worth bothering the backend with an
>> extra layer to manage the output of a data type.
>
> How about plugins on psql side? Calling hooked function in
> printQuery could do that on psql. Impact on psql itself is
> minimized. (Of course code for loading is omitted in the below
> but it would also small...)

That's interesting, and crazy. You would basically need to have the
equivalent of \load, or an environment variable like PSQL_SHARED_LIBS
that is similar to shared_preload_libraries on client-side. In short I
guess that's actually a clone of LD_PRELOAD.
--
Michael