From: | "Tomas Vondra" <tv(at)fuzzy(dot)cz> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Tomas Vondra" <tv(at)fuzzy(dot)cz>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: fdw_private and (List*) handling in FDW API |
Date: | 2013-10-18 16:06:04 |
Message-ID: | ddb8a34ba631a2e1b2a11d93d740bd0c.squirrel@sq.gransy.com |
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On 18 Říjen 2013, 17:52, Tom Lane wrote:
> "Tomas Vondra" <tv(at)fuzzy(dot)cz> writes:
>> 2) Is there any particular reason why
>> PlanForeignModify/BeginForeignModify
>> require the fdw_private to be a List*, and not a generic pointer?
>
> That data has to be copiable by copyObject(), which a generic void* is
> not. We could perhaps have made it Node* instead, but that would only
> work conveniently if there were infrastructure for plugins to create new
> first-class Node types; which there isn't. A List is often the easiest
> way to transport a few random values from plan time to execution time,
> so it seemed best to declare fdw_private that way.
Oh, I see. Thanks for explanation.
Tomas
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