Re: Allowing parallel-safe initplans

I looked further into this issue and I believe other places are good.
The problem with this query is that the es/ecxt_param_exec_vals used to
store info about the initplan is not the same one as in the Result
node's expression context for projection, because we've forked a new
process for the parallel worker and then created and initialized a new
EState node, and allocated a new es_param_exec_vals array for the new
EState.  When doing projection for the Result node, the current code
just goes ahead and accesses the new es_param_exec_vals, thus fails to
retrieve the info about the initplan.  Hmm, I doubt this is sensible.

So now it seems that the breakage of regression tests is more severe
than being cosmetic.  I wonder if we need to update the comments to
indicate the potential wrong results issue if we move the initPlans to
the Gather node.

Thanks
Richard