Hello
2013/8/5 David Gudeman <dave.gudeman@gmail.com>:
> For those who don't want to go to the link to see what I'm talking
> about with query rewrites, I thought I'd give a brief description.
> Foreign data wrappers currently do all of their work in the planning
> phase but I claim that isn't the right place to optimize foreign
> queries with aggregates and GROUP BY because optimizing those things
> would involve collapsing multiple plan node back into a single node
> for a foreign call. I propose to do these optimizations as query
> rewrites instead. So for example suppose t is a foreign table on the
> foreign server named fs. Then the query
>
> SELECT count(*) FROM t
>
> is rewritten to
>
> SELECT count FROM fs('select count(*) from t') fs(count bigint)
>
> where ts() is the pass-through query function for the server fs. To
> implement this optimization as a query rewrite, all of the elements of
> the result have to be real source-language constructs so the
> pass-through query has to be available in Postgresql SQL.
>
why you introduce new API? There is still dblink.
Regards
Pavel
> My current implementation of this uses a plugin that hooks into
> planner_hook, but I'm hoping that I can get some support for adding
> the query rewriting as callback functions for the FDW system.
>
> Regards,
> David Gudeman
> http://unobtainabol.blogspot.com
>
>
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