postgres-xc-developers

[Postgres-xc-developers] Detecting XC

[David E. W. <da...@ju...>]

PGXC Hackers,

What is the simplest way to tell if the server one has connected to is XC? Try to call pgxc_version()? `SHOW gtm_host`? Or is there something else to check, maybe something that doesn't throw an exception?

Thanks,

David

Re: [Postgres-xc-developers] Detecting XC

[Koichi S. <koi...@gm...>]

If you're detecting a datanode, you can do like this from any
available coordinator through psql:

EXECUTE DIRECT ON (nodename) 'SELECT 1';

If it is successful, the datanode is connected to the coordinator and
GTM is up and running.

You can detect a coordinator in the same way as vanilla PostgreSQL through psql:

SELECT 1;

They work when GTM is up and the coordinator is connected to GTM.
Anyway, without GTM up and running, the cluster won't work.

Please note that pgxc_ctl monitor command goes directly to datanodes
because it configures all the components.

Regards;

---
Koichi Suzuki


2014-02-05 David E. Wheeler <da...@ju...>:
> PGXC Hackers,
>
> What is the simplest way to tell if the server one has connected to is XC? Try to call pgxc_version()? `SHOW gtm_host`? Or is there something else to check, maybe something that doesn't throw an exception?
>
> Thanks,
>
> David
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Re: [Postgres-xc-developers] Detecting XC

[David E. W. <da...@ju...>]

On Feb 4, 2014, at 5:27 PM, Koichi Suzuki <koi...@gm...> wrote:

> You can detect a coordinator in the same way as vanilla PostgreSQL through psql:
> 
> SELECT 1;
> 
> They work when GTM is up and the coordinator is connected to GTM.
> Anyway, without GTM up and running, the cluster won't work.
> 
> Please note that pgxc_ctl monitor command goes directly to datanodes
> because it configures all the components.

No, what I want to know is if I have connected to XC and not PG.

D

Re: [Postgres-xc-developers] Detecting XC

[Koichi S. <koi...@gm...>]

Because XC didn't change libpq at all, I cannot find explicit way if
you're connecting to PG or XC.   Even psql binary from PG works with
XC.   I'd suggest to test if pgxc_class, pgxc_node and pgxc_nodegroup
catalog is available, which are all XC specifyc.   To avoid name
conflict (you can create table pgxc_class in PG), you can specify
pgxc_class oid value, which will be release-specific though.

Regards;
---
Koichi Suzuki


2014-02-05 David E. Wheeler <da...@ju...>:
> On Feb 4, 2014, at 5:27 PM, Koichi Suzuki <koi...@gm...> wrote:
>
>> You can detect a coordinator in the same way as vanilla PostgreSQL through psql:
>>
>> SELECT 1;
>>
>> They work when GTM is up and the coordinator is connected to GTM.
>> Anyway, without GTM up and running, the cluster won't work.
>>
>> Please note that pgxc_ctl monitor command goes directly to datanodes
>> because it configures all the components.
>
> No, what I want to know is if I have connected to XC and not PG.
>
> D
>

Re: [Postgres-xc-developers] Detecting XC

[David E. W. <da...@ju...>]

On Feb 4, 2014, at 5:36 PM, Koichi Suzuki <koi...@gm...> wrote:

> Because XC didn't change libpq at all, I cannot find explicit way if
> you're connecting to PG or XC.   Even psql binary from PG works with
> XC.   I'd suggest to test if pgxc_class, pgxc_node and pgxc_nodegroup
> catalog is available, which are all XC specifyc.   To avoid name
> conflict (you can create table pgxc_class in PG), you can specify
> pgxc_class oid value, which will be release-specific though.

I don’t think I need to be *that* anal. If someone creates a table named pgxc_class in pg_catalog then the problem is theirs, IMHO.

Thanks,

David

Re: [Postgres-xc-developers] Detecting XC

[Michael P. <mic...@gm...>]

On Wed, Feb 5, 2014 at 7:56 AM, David E. Wheeler <da...@ju...> wrote:
> PGXC Hackers,
>
> What is the simplest way to tell if the server one has connected to is XC? Try to call pgxc_version()? `SHOW gtm_host`? Or is there something else to check, maybe something that doesn't throw an exception?
How do you actually do for PG itself? Do you use PG_VERSION_NUM or similar?
-- 
Michael

Re: [Postgres-xc-developers] Detecting XC

[David E. W. <da...@ju...>]

On Feb 4, 2014, at 5:56 PM, Michael Paquier <mic...@gm...> wrote:

> How do you actually do for PG itself? Do you use PG_VERSION_NUM or similar?

I don’t. Previously I did not have to distinguish Postgres from anything else.

David

Re: [Postgres-xc-developers] Detecting XC

[Tatsuo I. <is...@po...>]

> PGXC Hackers,
> 
> What is the simplest way to tell if the server one has connected to is XC? Try to call pgxc_version()? `SHOW gtm_host`? Or is there something else to check, maybe something that doesn't throw an exception?

What about this?

SELECT count(*) from
	   (SELECT has_function_privilege('%s', 'pgxc_version(text)', 'execute')
	   WHERE EXISTS(SELECT * FROM pg_catalog.pg_proc AS p WHERE p.proname = 'pgxc_version')) AS s"

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

Re: [Postgres-xc-developers] Detecting XC

[David E. W. <da...@ju...>]

On Feb 5, 2014, at 5:33 PM, Tatsuo Ishii <is...@po...> wrote:

> What about this?
> 
> SELECT count(*) from
> 	   (SELECT has_function_privilege('%s', 'pgxc_version(text)', 'execute')
> 	   WHERE EXISTS(SELECT * FROM pg_catalog.pg_proc AS p WHERE p.proname = 'pgxc_version')) AS s"

I don’t much care about permission, so I would just do

    SELECT TRUE
      FROM pg_catalog.pg_proc p
      JOIN pg_catalog.pg_namespace n ON p.pronamespace = n.oid
     WHERE nspname = 'pg_catalog'
       AND proname = 'pgxc_version';

Best,

David