cj-zhukov commented on code in PR #21021:
URL: https://github.com/apache/datafusion/pull/21021#discussion_r3008529964
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datafusion/core/src/dataframe/mod.rs:
##########
@@ -410,21 +412,102 @@ impl DataFrame {
expr_list: impl IntoIterator<Item = impl Into<SelectExpr>>,
) -> Result<DataFrame> {
let expr_list: Vec<SelectExpr> =
- expr_list.into_iter().map(|e| e.into()).collect::<Vec<_>>();
+ expr_list.into_iter().map(|e| e.into()).collect();
+ // Extract expressions
let expressions = expr_list.iter().filter_map(|e| match e {
SelectExpr::Expression(expr) => Some(expr),
_ => None,
});
- let window_func_exprs = find_window_exprs(expressions);
- let plan = if window_func_exprs.is_empty() {
+ // Apply window functions first
+ let window_func_exprs = find_window_exprs(expressions.clone());
+
+ let mut plan = if window_func_exprs.is_empty() {
self.plan
} else {
LogicalPlanBuilder::window_plan(self.plan, window_func_exprs)?
};
- let project_plan =
LogicalPlanBuilder::from(plan).project(expr_list)?.build()?;
+ // Collect aggregate expressions
+ let aggr_exprs = find_aggregate_exprs(expressions.clone());
+
+ // Check for non-aggregate expressions
+ let has_non_aggregate_expr = expressions
+ .clone()
+ .any(|expr|
find_aggregate_exprs(std::iter::once(expr)).is_empty());
+
+ // Fallback to projection:
+ // - already aggregated
+ // - contains non-aggregate expressions
+ // - no aggregates
+ if matches!(plan, LogicalPlan::Aggregate(_))
+ || has_non_aggregate_expr
+ || aggr_exprs.is_empty()
+ {
+ let project_plan =
+ LogicalPlanBuilder::from(plan).project(expr_list)?.build()?;
+
+ return Ok(DataFrame {
+ session_state: self.session_state,
+ plan: project_plan,
+ projection_requires_validation: false,
+ });
+ }
+
+ // Assign aliases to aggregate expressions
+ let mut aggr_map: HashMap<Expr, Expr> = HashMap::new();
+ let mut used_names = HashSet::new();
+ let aggr_exprs_with_alias: Vec<Expr> = aggr_exprs
+ .into_iter()
+ .map(|expr| {
+ let base_name = expr.name_for_alias()?;
+ let mut name = base_name.clone();
+ let mut counter = 1;
+ while used_names.contains(&name) {
+ name = format!("{base_name}_{counter}");
+ counter += 1;
+ }
+ used_names.insert(name.clone());
+ let aliased = expr.clone().alias(name.clone());
+ let col = Expr::Column(Column::from_name(name));
+ aggr_map.insert(expr, col);
+ Ok(aliased)
+ })
+ .collect::<Result<Vec<_>>>()?;
+
+ // Build aggregate plan
+ plan = LogicalPlanBuilder::from(plan)
+ .aggregate(Vec::<Expr>::new(), aggr_exprs_with_alias)?
+ .build()?;
+
+ // Rewrite expressions to use aggregate outputs
+ let rewrite_expr = |expr: Expr, aggr_map: &HashMap<Expr, Expr>| ->
Result<Expr> {
+ expr.transform(|e| {
+ Ok(match aggr_map.get(&e) {
+ Some(replacement) => Transformed::yes(replacement.clone()),
+ None => Transformed::no(e),
+ })
+ })
+ .map(|t| t.data)
+ };
+
+ let mut rewritten_exprs = Vec::with_capacity(expr_list.len());
+ for select_expr in expr_list.into_iter() {
+ match select_expr {
+ SelectExpr::Expression(expr) => {
+ let rewritten = rewrite_expr(expr.clone(), &aggr_map)?;
+ let alias = expr.name_for_alias()?;
+
rewritten_exprs.push(SelectExpr::Expression(rewritten.alias(alias)));
Review Comment:
I agree with you
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