Re: read-only planner input

Qingqing Zhou wrote:
> So is this change the preparation work of caching query plans? Like cleaning
> the plans so they could be well shared?

Yeah, it is somewhat related to the centralized plan caching module that 
Tom and I have been discussing in the "cached plan invalidation" thread. 
When a cached plan has become invalidated, we want to re-run the planner 
on the original Query that has been saved away. If the planner modifies 
its input, that means we need to copy the Query it before passing it to 
the planner. While that is trivial to do, it is enough of an ugly hack 
that I decided to sit down and fix this problem before doing the rest of 
the cached plan invalidation work. Hopefully I haven't bitten off more 
than I can chew, so to speak :)

-Neil