Re: Read-only plan trees

Tom Lane wrote:
> Either of these approaches would mean that we couldn't easily "just
> execute" a scalar expression tree, which is something that we do in
> quite a few places (constraint checking for instance).  There would need
> to be some advance setup done.  With the Param-style approach, the
> advance setup would not be read-only on the expression plan tree ...
> which seems like a bad idea, so I'm leaning towards building the more
> expensive data structure.

Even though the former is a bit more expensive, it sounds like it is still a 
net win due to reduced/eliminated need for making plan tree copies, right? It 
sounds like it is also simpler and easier to maintain.

> Step 3: only after all the above spadework is done could we actually set
> up a query-lifetime memory context and build the executor's state in it.
> 
> Comments?

Sounds like a great plan. Let me know if there's anything I can do to help.

Joe