Re: Extension to rewrite queries before execution - Mailing list pgsql-general

From Melvin Davidson
Subject Re: Extension to rewrite queries before execution
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Msg-id CANu8Fiyuz6Q3DN_wPPfvxx215ZEZ3c4KRcsYtVOu8AGrdgaP3A@mail.gmail.com
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In response to Extension to rewrite queries before execution  (Jeff Janes <jeff.janes@gmail.com>)
Responses Re: Extension to rewrite queries before execution
Re: Extension to rewrite queries before execution
List pgsql-general
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.

On Thu, Aug 13, 2015 at 3:49 PM, Jeff Janes <jeff.janes@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.

Thanks,

Jeff



--
Melvin Davidson
I reserve the right to fantasize.  Whether or not you
wish to share my fantasy is entirely up to you.

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