postgres-xc-developers Mailing List for Postgres-XC

On Wed, Jul 20, 2011 at 5:56 AM, Michael Paquier
<mic...@gm...>wrote:

> Even if the method of parameters is a good approach, I am still wondering
> if it makes the implementation easier or not.
> Is there a basic mechanism in Postgres that permits to transform an
> expression function into a parameter?
>
> I am also wondering about cases where you may have functions calling other
> functions.
> date_trunc(now()), statement_timestamp - transaction_timestamp, etc.
>
> Maybe we may need some new basic mechanism to be able to support queries
> like:
> create sequence foo;
> create table footab (a int);
> INSERT INTO footab values (nextval('foo'));
>
> This could be a new node type that could be used inside RemoteQuery plans
> to deal with non-immutable functions feed.
> And the remote query plan may be able to rebuild the query in a correct way
> before pushing it down to nodes.
> But I am still new to those mechanisms so perhaps my words are not adapted.
> Any help is welcome of course.
>

Not sure, but take a look at ExecEvalParamExec and in general ParamExec
usage.


>
> On Tue, Jul 19, 2011 at 4:02 PM, Ashutosh Bapat <
> ash...@en...> wrote:
>
>>
>>
>>>
>>>> Hmm, I didn't think of this case :(
>>>>
>>>> I think, this will be a generic problem, if the queries other than
>>>> INSERT also use nextval() on sequences. There is less probability that
>>>> SELECT will use it but UPDATEs are other potential candidates.
>>>>
>>> Yes, you got a point here.
> I am just wondering about what kind of mechanisms I could borrow or extend
> in Postgres to support such things.
> Those basics are necessary for the feed of non-immutable functions, and its
> design should be done with care.
> --
> Michael Paquier
> http://michael.otacoo.com
>



-- 
Best Wishes,
Ashutosh Bapat
EntepriseDB Corporation
The Enterprise Postgres Company

Even if the method of parameters is a good approach, I am still wondering if
it makes the implementation easier or not.
Is there a basic mechanism in Postgres that permits to transform an
expression function into a parameter?

I am also wondering about cases where you may have functions calling other
functions.
date_trunc(now()), statement_timestamp - transaction_timestamp, etc.

Maybe we may need some new basic mechanism to be able to support queries
like:
create sequence foo;
create table footab (a int);
INSERT INTO footab values (nextval('foo'));

This could be a new node type that could be used inside RemoteQuery plans to
deal with non-immutable functions feed.
And the remote query plan may be able to rebuild the query in a correct way
before pushing it down to nodes.
But I am still new to those mechanisms so perhaps my words are not adapted.
Any help is welcome of course.

On Tue, Jul 19, 2011 at 4:02 PM, Ashutosh Bapat <
ash...@en...> wrote:

>
>
>>
>>> Hmm, I didn't think of this case :(
>>>
>>> I think, this will be a generic problem, if the queries other than INSERT
>>> also use nextval() on sequences. There is less probability that SELECT will
>>> use it but UPDATEs are other potential candidates.
>>>
>> Yes, you got a point here.
I am just wondering about what kind of mechanisms I could borrow or extend
in Postgres to support such things.
Those basics are necessary for the feed of non-immutable functions, and its
design should be done with care.
-- 
Michael Paquier
http://michael.otacoo.com