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31 changes: 14 additions & 17 deletions datafusion/optimizer/src/single_distinct_to_groupby.rs
Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ fn optimize(plan: &LogicalPlan) -> Result<LogicalPlan> {
schema,
group_expr,
}) => {
if is_single_distinct_agg(plan) && !contains_grouping_set(group_expr) {
if is_single_distinct_agg(plan)? && !contains_grouping_set(group_expr) {
let mut group_fields_set = HashSet::new();
let base_group_expr = grouping_set_to_exprlist(group_expr)?;
let mut all_group_args: Vec<Expr> = group_expr.clone();
Expand Down Expand Up @@ -159,27 +159,24 @@ fn optimize_children(plan: &LogicalPlan) -> Result<LogicalPlan> {
from_plan(plan, &expr, &new_inputs)
}

fn is_single_distinct_agg(plan: &LogicalPlan) -> bool {
fn is_single_distinct_agg(plan: &LogicalPlan) -> Result<bool> {
match plan {
LogicalPlan::Aggregate(Aggregate { aggr_expr, .. }) => {
let mut fields_set = HashSet::new();
aggr_expr
.iter()
.filter(|expr| {
let mut is_distinct = false;
if let Expr::AggregateFunction { distinct, args, .. } = expr {
is_distinct = *distinct;
args.iter().for_each(|expr| {
fields_set.insert(expr.name().unwrap());
})
let mut count = 0;
for expr in aggr_expr {
if let Expr::AggregateFunction { distinct, args, .. } = expr {
if *distinct {
count += 1;
}
is_distinct
})
.count()
== aggr_expr.len()
&& fields_set.len() == 1
for expr in args {
fields_set.insert(expr.name()?);
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Higher-order functions look good on interview code, but they could use a better story regarding error-propagation :/

}
}
}
Ok(count == aggr_expr.len() && fields_set.len() == 1)
}
_ => false,
_ => Ok(false),
}
}

Expand Down