Re: Extension to rewrite queries before execution

On 8/13/2015 2:49 PM, Jeff Janes 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.
>
> Thanks,
>
> Jeff

Have you looked at pg_bouncer?  You'd have to make changes to the
source, but it's got a bunch of what you'd need.  It sits in the middle
and could swap out text pretty easy.  I'd guess.

-Andy