Re: Questions and experiences writing a Foreign Data Wrapper

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