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alamb avatar alamb commented on August 17, 2024 1

Thanks @Rachelint -- I also have some time later this week to help with this issue (if it might help to have one or two examples as we work through #11151)

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Rachelint avatar Rachelint commented on August 17, 2024 1

Sounds like it might work -- I think the only way to really know for sure would be to try it out

Thanks, I try it now.

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Rachelint avatar Rachelint commented on August 17, 2024 1

Sounds like it might work -- I think the only way to really know for sure would be to try it out

Thanks, I try it now.

@Rachelint if you stop working on this could you please let me know?

Sorry for delay, still working on now, will try to push codes today...

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Rachelint avatar Rachelint commented on August 17, 2024

take

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Rachelint avatar Rachelint commented on August 17, 2024

Hi @alamb , I have some questions about the alternatives mentioned in the issue.
It seems the interface should be like:

trait AggregateExpr {
	fn output_from_stats(&self, stats: &Statistics) -> Option<ScalarValue> { None }
	...
}

As I understand, it is a optimization takes effect when specific aggregate functions(such as max, min, count...) can get the results directly from stats?

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alamb avatar alamb commented on August 17, 2024

As I understand, it is a optimization takes effect when specific aggregate functions(such as max, min, count...) can get the results directly from stats?

Yes that is the case

I think output_from_stats would also be reasonable and potentially more general. One challenge is that the AggregateExpr might not have access to its argument exprs (and thus it might not know what the argument is) 🤔

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Rachelint avatar Rachelint commented on August 17, 2024

As I understand, it is a optimization takes effect when specific aggregate functions(such as max, min, count...) can get the results directly from stats?

Yes that is the case

I think output_from_stats would also be reasonable and potentially more general. One challenge is that the AggregateExpr might not have access to its argument exprs (and thus it might not know what the argument is) 🤔

It seems a function expressions exists, and can help？

datafusion/datafusion/physical-expr-common/src/aggregate/mod.rs

Line 121 in 569be9e

fn expressions(&self) -> Vec<Arc<dyn PhysicalExpr>>;

and it is used to get min/max from stats now?

datafusion/datafusion/core/src/physical_optimizer/aggregate_statistics.rs

Lines 250 to 257 in 569be9e

if casted_expr.expressions().len() == 1 {
// TODO optimize with exprs other than Column
if let Some(col_expr) = casted_expr.expressions()[0]
.as_any()
.downcast_ref::<expressions::Column>()
{
if let Precision::Exact(val) =
&col_stats[col_expr.index()].max_value

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alamb avatar alamb commented on August 17, 2024

Sounds like it might work -- I think the only way to really know for sure would be to try it out

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edmondop avatar edmondop commented on August 17, 2024

Sounds like it might work -- I think the only way to really know for sure would be to try it out

Thanks, I try it now.

@Rachelint if you stop working on this could you please let me know?

from arrow-datafusion.

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