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refactor: rm single_distinct_to_groupby optimizer pass #15099

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refactor: rm single_distinct_to_groupby optimizer pass #15099

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1 change: 0 additions & 1 deletion datafusion/optimizer/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,6 @@ pub mod push_down_limit;
pub mod replace_distinct_aggregate;
pub mod scalar_subquery_to_join;
pub mod simplify_expressions;
pub mod single_distinct_to_groupby;
pub mod utils;

#[cfg(test)]
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2 changes: 0 additions & 2 deletions datafusion/optimizer/src/optimizer.rs
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Expand Up @@ -53,7 +53,6 @@ use crate::push_down_limit::PushDownLimit;
use crate::replace_distinct_aggregate::ReplaceDistinctWithAggregate;
use crate::scalar_subquery_to_join::ScalarSubqueryToJoin;
use crate::simplify_expressions::SimplifyExpressions;
use crate::single_distinct_to_groupby::SingleDistinctToGroupBy;
use crate::utils::log_plan;

/// `OptimizerRule`s transforms one [`LogicalPlan`] into another which
Expand Down Expand Up @@ -240,7 +239,6 @@ impl Optimizer {
// Filters can't be pushed down past Limits, we should do PushDownFilter after PushDownLimit
Arc::new(PushDownLimit::new()),
Arc::new(PushDownFilter::new()),
Arc::new(SingleDistinctToGroupBy::new()),
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Queries like avg(distinct a) rely on this rule, and without it, they cannot be executed anymore.

The following query is available on the main branch, but not on this PR branch.

DataFusion CLI v46.0.0
> select avg(distinct a) from values(1) t(a);
Execution error: avg(DISTINCT) aggregations are not available

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@alamb alamb Mar 11, 2025 •
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The alternative would be to directly implement distinct support in the avg accumulator

The lack of avg support means we can't run multiple distinct avg aggregates

> select avg(distinct a), avg(distinct b) from values(1, 2) t(a, b);
Execution error: avg(DISTINCT) aggregations are not available

This is tracked by

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I also updated the ticket #2408 to explain the issue and a bit more about what is needed

// The previous optimizations added expressions and projections,
// that might benefit from the following rules
Arc::new(SimplifyExpressions::new()),
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