Обсуждение: Execute a function through fdw

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Execute a function through fdw

От
Patrick FICHE
Дата:

Hello,

 

Is it possible to execute a function located on a server accessed through Postgres fdw.

This function returns a TABLE structure.

 

I have mapped rmt_schema and there is a function called Get_Tables in this schema.

I would like to execute something like :

SELECT * FROM rmt_schema.Get_Tables();

 

Or is it required to create a local function that will access to remote tables in order to achieve the same result ?

 

Regards,

 

Patrick Fiche

e. patrick.fiche@aqsacom.com

 

 

Вложения

Re: Execute a function through fdw

От
Guillaume Lelarge
Дата:
Le ven. 18 oct. 2019 à 11:51, Patrick FICHE <Patrick.Fiche@aqsacom.com> a écrit :

Hello,

 

Is it possible to execute a function located on a server accessed through Postgres fdw.

This function returns a TABLE structure.

 

I have mapped rmt_schema and there is a function called Get_Tables in this schema.

I would like to execute something like :

SELECT * FROM rmt_schema.Get_Tables();

 

Or is it required to create a local function that will access to remote tables in order to achieve the same result ?


It's probably easier to create a view on the remote server, and access it as a foreign table on the local server.

Re: Execute a function through fdw

От
Tom Lane
Дата:
Guillaume Lelarge <guillaume@lelarge.info> writes:
> Le ven. 18 oct. 2019 à 11:51, Patrick FICHE <Patrick.Fiche@aqsacom.com> a
> écrit :
>> Is it possible to execute a function located on a server accessed through
>> Postgres fdw.

> It's probably easier to create a view on the remote server, and access it
> as a foreign table on the local server.

Yeah.  Or if you really want to call a remote function by name, see
dblink.  postgres_fdw actively avoids doing that sort of thing.

            regards, tom lane

RE: Execute a function through fdw

От
Patrick FICHE
Дата:
Thanks a lot for your answer.
Using a view is really a good solution for my case.
As I already use fdw for some other cases, I prefer not to mix with dblink.

Regards,

Patrick Fiche



-----Original Message-----
From: Tom Lane <tgl@sss.pgh.pa.us> 
Sent: Friday, October 18, 2019 1:55 PM
To: Guillaume Lelarge <guillaume@lelarge.info>
Cc: Patrick FICHE <Patrick.Fiche@aqsacom.com>; pgsql-generallists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Execute a function through fdw

Guillaume Lelarge <guillaume@lelarge.info> writes:
> Le ven. 18 oct. 2019 à 11:51, Patrick FICHE 
> <Patrick.Fiche@aqsacom.com> a écrit :
>> Is it possible to execute a function located on a server accessed 
>> through Postgres fdw.

> It's probably easier to create a view on the remote server, and access 
> it as a foreign table on the local server.

Yeah.  Or if you really want to call a remote function by name, see dblink.  postgres_fdw actively avoids doing that
sortof thing.
 

            regards, tom lane

RE: Execute a function through fdw

От
Patrick FICHE
Дата:
Hi,

I got one more issue after I created my view.

I created it on my Server 1 but I am unable to view it on the Server 2.
I can see all tables through fdw after IMPORT FOREIGN SCHEMA.

I was able to get access to my view only after recreating the SERVER / USER MAPPING on Server 2.

Is it the expected behavior to recreate the FOREIGN SERVER / SCHEMA after a new table or view has been created ?

Regards,


Patrick Fiche
Database Engineer, Aqsacom Sas.
c. 33 6 82 80 69 96 



-----Original Message-----
From: Patrick FICHE <Patrick.Fiche@aqsacom.com> 
Sent: Friday, October 18, 2019 2:35 PM
To: Tom Lane <tgl@sss.pgh.pa.us>; Guillaume Lelarge <guillaume@lelarge.info>
Cc: pgsql-generallists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: RE: Execute a function through fdw

Thanks a lot for your answer.
Using a view is really a good solution for my case.
As I already use fdw for some other cases, I prefer not to mix with dblink.

Regards,

Patrick Fiche



-----Original Message-----
From: Tom Lane <tgl@sss.pgh.pa.us>
Sent: Friday, October 18, 2019 1:55 PM
To: Guillaume Lelarge <guillaume@lelarge.info>
Cc: Patrick FICHE <Patrick.Fiche@aqsacom.com>; pgsql-generallists.postgresql.org <pgsql-general@lists.postgresql.org>
Subject: Re: Execute a function through fdw

Guillaume Lelarge <guillaume@lelarge.info> writes:
> Le ven. 18 oct. 2019 à 11:51, Patrick FICHE 
> <Patrick.Fiche@aqsacom.com> a écrit :
>> Is it possible to execute a function located on a server accessed 
>> through Postgres fdw.

> It's probably easier to create a view on the remote server, and access 
> it as a foreign table on the local server.

Yeah.  Or if you really want to call a remote function by name, see dblink.  postgres_fdw actively avoids doing that
sortof thing.
 

            regards, tom lane

Re: Execute a function through fdw

От
Guillaume Lelarge
Дата:
Le ven. 18 oct. 2019 à 17:53, Patrick FICHE <Patrick.Fiche@aqsacom.com> a écrit :
Hi,

I got one more issue after I created my view.

I created it on my Server 1 but I am unable to view it on the Server 2.
I can see all tables through fdw after IMPORT FOREIGN SCHEMA.

I was able to get access to my view only after recreating the SERVER / USER MAPPING on Server 2.

Is it the expected behavior to recreate the FOREIGN SERVER / SCHEMA after a new table or view has been created ?

No, you don't need to re create the foreign server. How did it not work?

RE: Execute a function through fdw

От
Patrick FICHE
Дата:

Le ven. 18 oct. 2019 à 17:53, Patrick FICHE <Patrick.Fiche@aqsacom.com> a écrit :

Hi,

I got one more issue after I created my view.

I created it on my Server 1 but I am unable to view it on the Server 2.
I can see all tables through fdw after IMPORT FOREIGN SCHEMA.

I was able to get access to my view only after recreating the SERVER / USER MAPPING on Server 2.

Is it the expected behavior to recreate the FOREIGN SERVER / SCHEMA after a new table or view has been created ?

 

| No, you don't need to re create the foreign server. How did it not work?

 

After I created the view on the server 1, I tried to import it in the Foreign Schema on Server 2 using the LIMITED clause.

The command executed successfully but when I tried to query the view on server 2, it returned that table did not exist.

 

So, I tried to reimport the full schema (after dropping / creating the schema on server 2), I ran the IMPORT FOREIGN SCHEMA without any LIMITED clause. I could see all tables but still not the view.

 

The only solution that I found in order to get the view accessible on Server 2 was to recreate the SERVER / USER MAPPING and IMPORT FOREIGN SCHEMA.

 

My Postgres versions on both servers is 11.5.

 

Regards,

 

Re: Execute a function through fdw

От
Jeff Janes
Дата:


On Fri, Oct 18, 2019 at 7:55 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Guillaume Lelarge <guillaume@lelarge.info> writes:
> Le ven. 18 oct. 2019 à 11:51, Patrick FICHE <Patrick.Fiche@aqsacom.com> a
> écrit :
>> Is it possible to execute a function located on a server accessed through
>> Postgres fdw.

> It's probably easier to create a view on the remote server, and access it
> as a foreign table on the local server.

Yes, that would probably work here, but if the function takes user-supplied arguments, that won't work. 

Yeah.  Or if you really want to call a remote function by name, see
dblink.  postgres_fdw actively avoids doing that sort of thing.

And importantly, you can specify the name of the existing postgres_fdw server to the dblink functions in place of the connection string.  This removes quite a bit of the drudgery of using dblink, if you are already using postgres_fdw.
 
Cheers,

Jeff