Jeff, although it would be tedious, you could write a trigger of the form BEFORE INSERT ON yatta_yatta EXECUTE PROCEDURE check_rewrite;
Then in check_rewrite, you could examine the contents of pg_stat_activity.query column for the current process and act accordingly. I acknowledge that it will impact performance, but I see no other way to accomplish what you wish. At the very least, you would be able to issue the "set enable_* =off;" or "set work_mem=*; inside the procedure. That is the best I can suggest. On Fri, Aug 14, 2015 at 11:53 AM, Jeff Janes <jeff.ja...@gmail.com> wrote: > > On Thu, Aug 13, 2015 at 1:37 PM, Melvin Davidson <melvin6...@gmail.com> > wrote: > > >> On Thu, Aug 13, 2015 at 3:49 PM, Jeff Janes <jeff.ja...@gmail.com> wrote: >> >>> I am looking for an extension or a technique that will allow me to >>> intercept a query by the exact query text, and replace that query with a >>> different one. >>> >>> The context is running a third-party app which issues queries I have no >>> control over. I'd like to intercept a specific query (which has no bind >>> parameters) and either replace the query text with a different text which, >>> for example, swaps out an "in list" clause to instead be an "exists >>> (subquery)". >>> >>> Or just wrap the query in a "set enable_* =off;" or "set work_mem=*;" >>> before and a reset of it after. >>> >>> Is there anything out there like this? This would be for 9.4. >>> >>> I'm willing to put the query text, and its replacement, directly into >>> the extension source code and compile it, but of course something more >>> flexible would be ideal. >>> >>> > > You have not stated which Version or PostgreSQL, nor the O/S involved. >> That being said, depending on what the specific query is, you might >> consider using a Rule or Trigger to handle it. If you use a Trigger ( which >> is the preferred method) you can also embed "set" commands the associated >> function. >> > > Sure I did, 9.4. OS would be Linux, although I would hope a solution > would be work. If you mean the built-in-to-core rules or triggers, those > wouldn't work. Neither one allows you to rewrite a where clause as far as > I can tell. Rules allows you add one, but not more than that. And > triggers don't exists for select queries. > > Cheers, > > Jeff > -- *Melvin Davidson* I reserve the right to fantasize. Whether or not you wish to share my fantasy is entirely up to you.
