Re: NOT EXIST for PREPARE

On Wed, Mar 23, 2016 at 7:27 AM, Craig Ringer <craig(at)2ndquadrant(dot)com> wrote:
> With PREPARE IF NOT EXISTS the client is also paying parse and network
> overhead for every time you send that statement. Much better not to send it
> repeatedly in the first place.

How did you determine that? The client prepares the statement exactly
once. The problem is there's no easy way to determine if someone else
prepared it first and this patch directly addresses that.

> I think we need to take a step back here and better define the problem
> before stepping in with a proposed solution. Something that avoids the need
> to spam the server with endless copies of the same PREPARE statements would
> be good.

I'm not understanding the objection at all. You have N client
sessions connecting to the database that all utilize the same named
prepared statement. A typical pattern is for the application to
prepare them all upon startup, but currently each PREPARE needs to be
wrapped with an exception handler in case someone else prepared it
first. Having an IF NOT EXISTS decoration simplifies this. This can
happen both inside and outside of connection pooling scenarios.

merlin