Re: [HACKERS] path toward faster partition pruning

On Mon, May 07, 2018 at 10:37:10AM +0900, Michael Paquier wrote:
> On Fri, May 04, 2018 at 12:32:23PM +0300, Marina Polyakova wrote:
> > I got a similar server crash as in [1] on the master branch since the commit
> > 9fdb675fc5d2de825414e05939727de8b120ae81 when the assertion fails because
> > the second argument ScalarArrayOpExpr is not a Const or an ArrayExpr, but is
> > an ArrayCoerceExpr (see [2]):
>
> Indeed, I can see the crash.  I have been playing with this stuff and I
> am in the middle of writing the patch, but let's track this properly for
> now.

So the problem appears when an expression needs to use
COERCION_PATH_ARRAYCOERCE for a type coercion from one type to another,
which requires an execution state to be able to build the list of
elements.  The clause matching happens at planning state, so while there
are surely cases where this could be improved depending on the
expression type, I propose to just discard all clauses which do not
match OpExpr and ArrayExpr for now, as per the attached.  It would be
definitely a good practice to have a default code path returning
PARTCLAUSE_UNSUPPORTED where the element list cannot be built.

Thoughts?
--
Michael