From: | "Albe Laurenz" <laurenz(dot)albe(at)wien(dot)gv(dot)at> |
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To: | "Heikki Linnakangas *EXTERN*" <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
Cc: | <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Questions and experiences writing a Foreign Data Wrapper |
Date: | 2011-07-21 07:32:15 |
Message-ID: | D960CB61B694CF459DCFB4B0128514C206ABA030@exadv11.host.magwien.gv.at |
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Heikki Linnakangas wrote:
>> 2) If I decide to close remote database connections after
>> use, I would like to do so where reasonable.
>> I would like to keep the connection open between query
>> planning and query execution and close it when the
>> scan is done.
>> The exception could be named prepared statements.
>> Is there a way to tell if that is the case during
>> planing or execution?
> Hmm, maybe you could add a hook to close the connection when the
> transaction ends. But actually, you'd want to keep the connection
> open across transactions too. Some sort of a general connection
> caching facility would be useful for many FDW.
I agree, and that is how I implemented it at the moment.
But it might be nice to give the user the option, say, if they know
that it is a long session in a daemon process that accesses the
remote table only once a day.
I'll look into the hook option.
Here are some more ideas for FDW API functions/macros that might be
useful for FDW developers.
- A function that gives you the internal and external parameters at
execution time.
- A function that gives you a type's input and output function.
- A function that gives you the OID of the foreign table owner.
- A function that gives you the list of columns of the foreign
table (atttypid, atttypmod, attname, maybe others).
Yours,
Laurenz Albe
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