Mingda,
I'm not sure how much re-ordering can be done at the Hyracks level,
i.e., the runtime level.
In the optimizer (the asterixdb/algebricks level), we don't have
re-ordering for joins, because:
--- the cost model has not been added yet. I'm not sure about the
timeline for this. @Ildar?
--- respecting user-specified join orders is important for certain
cases, for example, to get stable/predictable performance (zero surprise)
for applications.
In the runtime, we have a role-reversal optimization in hybrid hash
join, which is a safe optimization that is not based on estimations. You
can look at OptimizedHybridHashJoin.
Best,
Yingyi
On Mon, Oct 31, 2016 at 11:16 AM, mingda li <[email protected]> wrote:
> Dear all,
>
> Hi, I am working on multiple join on Hyracks level. I am not sure if I do
> the multiple join on AsterixDB, whether it will optimize the query by
> changing the join order or just execute according to how we write the
> query. I think this may not be done in Algebricks level based on rule but
> not sure.
>
> Bests,
> Mingda
>
