Re: Early WIP/PoC for inlining CTEs

On 1/1/19 1:42 AM, Andrew Gierth wrote:
>>>>>> "Andreas" == Andreas Karlsson <andreas(at)proxel(dot)se> writes:
>
> Andreas> I believe I have fixed these except for the comment on the
> Andreas> conditions for when we inline.
>
> Andreas> Andrew Gierth: Why did you chose to not inline on FOR UPDATE
> Andreas> but inline volatile functions? I feel that this might be
> Andreas> inconsistent since in both cases the query in the CTE can
> Andreas> change behavior if the planner pushes a WHERE clause into the
> Andreas> subquery, but maybe I am missing something.
>
> I chose not to inline FOR UPDATE because it was an obvious compatibility
> break, potentially changing the set of locked rows, and it was an easy
> condition to test.
>
> I did not test for volatile functions simply because this was a very
> early stage of the project (which wasn't my project, I was just
> assisting someone else). I left the comment "this likely needs some
> additional checks" there for a reason.

Thanks, that makes sense! I will need to ponder some on if the behavior
change when predicates are pushed into a subquery with volatile
functions is ok. I am leaning towards no, because otherwise inlining
CTEs would affect more than query performance.

Andreas