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Posted to dev@calcite.apache.org by Ian Bertolacci <ia...@workday.com.INVALID> on 2021/05/03 19:48:32 UTC

How to match root node in a HEP Rule?

Hello,
I am trying to write a rule that matches (among other things) the root of a RelNode tree.

Unfortunately, it seems that HepRuleCall.parents is only initialized and populated if the rule extends CommonRelSubExpr, which doesn’t really apply in my case.
(see: https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/plan/hep/HepPlanner.java#L526)

Is there a way to identify a node as being a root node during RelRule.match? Or more generally, is there a way to collect the parents of an arbitrary RelNode?

Thanks.

Re: How to match root node in a HEP Rule?

Posted by Stamatis Zampetakis <za...@gmail.com>.
Hi Ian,

There are some workarounds to find the root node inside a RelRule match but
these rules become planner specific.
For instance, Hive applies some workarounds (e.g., in
HiveFieldTrimmerRule[1]) for running inside rules, transformations that
apply and modify the whole plan.

Best,
Stamatis

[1]
https://github.com/apache/hive/blob/58b05f72f74dd35214c3d33c2008b16124fdb25f/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveFieldTrimmerRule.java#L30

On Tue, May 4, 2021 at 2:50 AM Haisheng Yuan <hy...@apache.org> wrote:

> Hi Ian,
>
> Is there any specific reason or use case that you have to match the root
> node and find the parent node in your customized rule?
>
> Thanks,
> Haisheng Yuan
>
> On 2021/05/03 20:20:22, Julian Hyde <jh...@apache.org> wrote:
> > > Is there a way to identify a node as being a root node during
> RelRule.match?
> >
> > Not currently. One workaround would be to create 'class MyRoot extends
> > SingleRel', add it as the root of the tree, and write your rules to
> > match on it.
> >
> > > Or more generally, is there a way to collect the parents of an
> arbitrary RelNode?
> >
> > By design, the only way to find the parents of a RelNode are to write
> > a rule that matches those parents. This ensures that rules will work
> > in the Volcano planner, where a RelNode can have many parents.
> >
> > Julian
> >
> > On Mon, May 3, 2021 at 12:52 PM Ian Bertolacci
> > <ia...@workday.com.invalid> wrote:
> > >
> > > Hello,
> > > I am trying to write a rule that matches (among other things) the root
> of a RelNode tree.
> > >
> > > Unfortunately, it seems that HepRuleCall.parents is only initialized
> and populated if the rule extends CommonRelSubExpr, which doesn’t really
> apply in my case.
> > > (see:
> https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/plan/hep/HepPlanner.java#L526
> )
> > >
> > > Is there a way to identify a node as being a root node during
> RelRule.match? Or more generally, is there a way to collect the parents of
> an arbitrary RelNode?
> > >
> > > Thanks.
> >
>

Re: How to match root node in a HEP Rule?

Posted by Haisheng Yuan <hy...@apache.org>.
Hi Ian,

Is there any specific reason or use case that you have to match the root node and find the parent node in your customized rule?

Thanks,
Haisheng Yuan

On 2021/05/03 20:20:22, Julian Hyde <jh...@apache.org> wrote: 
> > Is there a way to identify a node as being a root node during RelRule.match?
> 
> Not currently. One workaround would be to create 'class MyRoot extends
> SingleRel', add it as the root of the tree, and write your rules to
> match on it.
> 
> > Or more generally, is there a way to collect the parents of an arbitrary RelNode?
> 
> By design, the only way to find the parents of a RelNode are to write
> a rule that matches those parents. This ensures that rules will work
> in the Volcano planner, where a RelNode can have many parents.
> 
> Julian
> 
> On Mon, May 3, 2021 at 12:52 PM Ian Bertolacci
> <ia...@workday.com.invalid> wrote:
> >
> > Hello,
> > I am trying to write a rule that matches (among other things) the root of a RelNode tree.
> >
> > Unfortunately, it seems that HepRuleCall.parents is only initialized and populated if the rule extends CommonRelSubExpr, which doesn’t really apply in my case.
> > (see: https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/plan/hep/HepPlanner.java#L526)
> >
> > Is there a way to identify a node as being a root node during RelRule.match? Or more generally, is there a way to collect the parents of an arbitrary RelNode?
> >
> > Thanks.
>

Re: How to match root node in a HEP Rule?

Posted by Julian Hyde <jh...@apache.org>.
> Is there a way to identify a node as being a root node during RelRule.match?

Not currently. One workaround would be to create 'class MyRoot extends
SingleRel', add it as the root of the tree, and write your rules to
match on it.

> Or more generally, is there a way to collect the parents of an arbitrary RelNode?

By design, the only way to find the parents of a RelNode are to write
a rule that matches those parents. This ensures that rules will work
in the Volcano planner, where a RelNode can have many parents.

Julian

On Mon, May 3, 2021 at 12:52 PM Ian Bertolacci
<ia...@workday.com.invalid> wrote:
>
> Hello,
> I am trying to write a rule that matches (among other things) the root of a RelNode tree.
>
> Unfortunately, it seems that HepRuleCall.parents is only initialized and populated if the rule extends CommonRelSubExpr, which doesn’t really apply in my case.
> (see: https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/plan/hep/HepPlanner.java#L526)
>
> Is there a way to identify a node as being a root node during RelRule.match? Or more generally, is there a way to collect the parents of an arbitrary RelNode?
>
> Thanks.