We did have some hints for our physical rules to apply some strategies, the
very common case is the JOIN algorithm, such as the NESTED_LOOP,
SHUFFLE_HASH, SORT_MERGE and so on.
The only reason that I do not implement the physical hints for Calcite is
that I do not have enough time for that,
One principle we should apply here: if a so-called “hint” causes the physical
operator to have a different cost then it’s not a hint; it is a parameter. An
example would be the buffer size allocated to an external sort. You might
conceivably have two instances of that operator with different
There are use cases where it makes sense to keep/pass hints and others that
I assume makes sense to discard them (not used by the operator, rules,
implementors, etc).
Since the discussion was brought up for the Enumerable operators what's the
benefit of retaining hints at this level?
As far as I
+1 With Haisheng
Besides, seems we will lose hint even in the logical
plan, in RelBuilder#project, we just construct a project without
hints(ImmutableList.of()).
Regards!
Aron Tao
Haisheng Yuan 于2021年5月21日周五 上午9:20写道：
The hint can be used to specify the degree of parallelism (DOP), MIN/MAX
The hint can be used to specify the degree of parallelism (DOP), MIN/MAX memory
allocated for the operator. In that case, we need to keep them in the physical
operators. But I am not sure whether there are downstream projects that are
using hints for physical resource.
On 2021/05/19 17:05:44,
Sure, there’s a slot to hold the hints. But is there a benefit to keeping them
in the physical algebra? There is certainly a cost to storing them, propagating
them, fixing them up as we apply rules.
The main source of hints is formatted comments in the SQL. As we get further
from the SQL
Hi Julian
When hints were introduced, was that part of the plan?
"hint" is a field in the base class, so the type of the node doesn't matter
public abstract class Project extends SingleRel implements Hintable {
//~ Instance fields
Do we really need hints in physical operators? When hints were introduced, was
that part of the plan?
Julian
> On May 17, 2021, at 11:50 PM, JiaTao Tao wrote:
>
> Hi
> Recently, I'm integrating Calcite's hint into our system, and I've found
> the Enumerable rules just throw the hint
Hi
Recently, I'm integrating Calcite's hint into our system, and I've found
the Enumerable rules just throw the hint info(ImmutableList.of()) away:
public EnumerableProject(
RelOptCluster cluster,
RelTraitSet traitSet,
RelNode input,
List projects,
RelDataType
