Support unparsing plans with both Aggregation and Window functions (#35)

Author: sgrebnov

datafusion/sql/src/unparser/plan.rs

@@ -36,7 +36,10 @@ use super::{
         rewrite_plan_for_sort_on_non_projected_fields,
         subquery_alias_inner_query_and_columns,
     },
-    utils::{find_agg_node_within_select, unproject_window_exprs, AggVariant},
+    utils::{
+        find_agg_node_within_select, find_window_nodes_within_select,
+        unproject_window_exprs,
+    },
     Unparser,
 };
 
@@ -170,13 +173,17 @@ impl Unparser<'_> {
         p: &Projection,
         select: &mut SelectBuilder,
     ) -> Result<()> {
-        match find_agg_node_within_select(plan, None, true) {
-            Some(AggVariant::Aggregate(agg)) => {
+        match (
+            find_agg_node_within_select(plan, true),
+            find_window_nodes_within_select(plan, None, true),
+        ) {
+            (Some(agg), window) => {
+                let window_option = window.as_deref();
                 let items = p
                     .expr
                     .iter()
                     .map(|proj_expr| {
-                        let unproj = unproject_agg_exprs(proj_expr, agg)?;
+                        let unproj = unproject_agg_exprs(proj_expr, agg, window_option)?;
                         self.select_item_to_sql(&unproj)
                     })
                     .collect::<Result<Vec<_>>>()?;
@@ -190,7 +197,7 @@ impl Unparser<'_> {
                     vec![],
                 ));
             }
-            Some(AggVariant::Window(window)) => {
+            (None, Some(window)) => {
                 let items = p
                     .expr
                     .iter()
@@ -202,7 +209,7 @@ impl Unparser<'_> {
 
                 select.projection(items);
             }
-            None => {
+            _ => {
                 let items = p
                     .expr
                     .iter()
@@ -285,10 +292,10 @@ impl Unparser<'_> {
                 self.select_to_sql_recursively(p.input.as_ref(), query, select, relation)
             }
             LogicalPlan::Filter(filter) => {
-                if let Some(AggVariant::Aggregate(agg)) =
-                    find_agg_node_within_select(plan, None, select.already_projected())
+                if let Some(agg) =
+                    find_agg_node_within_select(plan, select.already_projected())
                 {
-                    let unprojected = unproject_agg_exprs(&filter.predicate, agg)?;
+                    let unprojected = unproject_agg_exprs(&filter.predicate, agg, None)?;
                     let filter_expr = self.expr_to_sql(&unprojected)?;
                     select.having(Some(filter_expr));
                 } else {

datafusion/sql/src/unparser/utils.rs

@@ -18,58 +18,81 @@
 use datafusion_common::{
     internal_err,
     tree_node::{Transformed, TreeNode},
-    Result,
+    Column, Result,
 };
 use datafusion_expr::{Aggregate, Expr, LogicalPlan, Window};
 
-/// One of the possible aggregation plans which can be found within a single select query.
-pub(crate) enum AggVariant<'a> {
-    Aggregate(&'a Aggregate),
-    Window(Vec<&'a Window>),
+/// Recursively searches children of [LogicalPlan] to find an Aggregate node if exists
+/// prior to encountering a Join, TableScan, or a nested subquery (derived table factor).
+/// If an Aggregate or node is not found prior to this or at all before reaching the end
+/// of the tree, None is returned.
+pub(crate) fn find_agg_node_within_select(
+    plan: &LogicalPlan,
+    already_projected: bool,
+) -> Option<&Aggregate> {
+    // Note that none of the nodes that have a corresponding node can have more
+    // than 1 input node. E.g. Projection / Filter always have 1 input node.
+    let input = plan.inputs();
+    let input = if input.len() > 1 {
+        return None;
+    } else {
+        input.first()?
+    };
+    // Agg nodes explicitly return immediately with a single node
+    if let LogicalPlan::Aggregate(agg) = input {
+        Some(agg)
+    } else if let LogicalPlan::TableScan(_) = input {
+        None
+    } else if let LogicalPlan::Projection(_) = input {
+        if already_projected {
+            None
+        } else {
+            find_agg_node_within_select(input, true)
+        }
+    } else {
+        find_agg_node_within_select(input, already_projected)
+    }
 }
 
-/// Recursively searches children of [LogicalPlan] to find an Aggregate or window node if one exists
+/// Recursively searches children of [LogicalPlan] to find Window nodes if exist
 /// prior to encountering a Join, TableScan, or a nested subquery (derived table factor).
-/// If an Aggregate or window node is not found prior to this or at all before reaching the end
-/// of the tree, None is returned. It is assumed that a Window and Aggregate node cannot both
-/// be found in a single select query.
-pub(crate) fn find_agg_node_within_select<'a>(
+/// If Window node is not found prior to this or at all before reaching the end
+/// of the tree, None is returned.
+pub(crate) fn find_window_nodes_within_select<'a>(
     plan: &'a LogicalPlan,
-    mut prev_windows: Option<AggVariant<'a>>,
+    mut prev_windows: Option<Vec<&'a Window>>,
     already_projected: bool,
-) -> Option<AggVariant<'a>> {
-    // Note that none of the nodes that have a corresponding agg node can have more
+) -> Option<Vec<&'a Window>> {
+    // Note that none of the nodes that have a corresponding node can have more
     // than 1 input node. E.g. Projection / Filter always have 1 input node.
     let input = plan.inputs();
     let input = if input.len() > 1 {
-        return None;
+        return prev_windows;
     } else {
         input.first()?
     };
 
-    // Agg nodes explicitly return immediately with a single node
     // Window nodes accumulate in a vec until encountering a TableScan or 2nd projection
     match input {
-        LogicalPlan::Aggregate(agg) => Some(AggVariant::Aggregate(agg)),
         LogicalPlan::Window(window) => {
             prev_windows = match &mut prev_windows {
-                Some(AggVariant::Window(windows)) => {
+                Some(windows) => {
                     windows.push(window);
                     prev_windows
                 }
-                _ => Some(AggVariant::Window(vec![window])),
+                _ => Some(vec![window]),
             };
-            find_agg_node_within_select(input, prev_windows, already_projected)
+            find_window_nodes_within_select(input, prev_windows, already_projected)
         }
         LogicalPlan::Projection(_) => {
             if already_projected {
                 prev_windows
             } else {
-                find_agg_node_within_select(input, prev_windows, true)
+                find_window_nodes_within_select(input, prev_windows, true)
             }
         }
         LogicalPlan::TableScan(_) => prev_windows,
-        _ => find_agg_node_within_select(input, prev_windows, already_projected),
+        _ => find_window_nodes_within_select(input, prev_windows, already_projected),
     }
 }
 
@@ -78,19 +101,30 @@ pub(crate) fn find_agg_node_within_select<'a>(
 ///
 /// For example, if expr contains the column expr "COUNT(*)" it will be transformed
 /// into an actual aggregate expression COUNT(*) as identified in the aggregate node.
-pub(crate) fn unproject_agg_exprs(expr: &Expr, agg: &Aggregate) -> Result<Expr> {
+pub(crate) fn unproject_agg_exprs(
+    expr: &Expr,
+    agg: &Aggregate,
+    windows: Option<&[&Window]>,
+) -> Result<Expr> {
     expr.clone()
         .transform(|sub_expr| {
             if let Expr::Column(c) = sub_expr {
-                // find the column in the agg schema
-                if let Ok(n) = agg.schema.index_of_column(&c) {
-                    let unprojected_expr = agg
-                        .group_expr
-                        .iter()
-                        .chain(agg.aggr_expr.iter())
-                        .nth(n)
-                        .unwrap();
+                if let Some(unprojected_expr) = find_agg_expr(agg, &c) {
                     Ok(Transformed::yes(unprojected_expr.clone()))
+                } else if let Some(mut unprojected_expr) =
+                    windows.and_then(|w| find_window_expr(w, &c.name).cloned())
+                {
+                    if let Expr::WindowFunction(func) = &mut unprojected_expr {
+                        // Window function can contain aggregation column, for ex 'avg(sum(ss_sales_price)) over ..' that needs to be unprojected
+                        for arg in &mut func.args {
+                            if let Expr::Column(c) = arg {
+                                if let Some(expr) = find_agg_expr(agg, c) {
+                                    *arg = expr.clone();
+                                }
+                            }
+                        }
+                    }
+                    Ok(Transformed::yes(unprojected_expr))
                 } else {
                     internal_err!(
                         "Tried to unproject agg expr not found in provided Aggregate!"
@@ -112,11 +146,7 @@ pub(crate) fn unproject_window_exprs(expr: &Expr, windows: &[&Window]) -> Result
     expr.clone()
         .transform(|sub_expr| {
             if let Expr::Column(c) = sub_expr {
-                if let Some(unproj) = windows
-                    .iter()
-                    .flat_map(|w| w.window_expr.iter())
-                    .find(|window_expr| window_expr.schema_name().to_string() == c.name)
-                {
+                if let Some(unproj) = find_window_expr(windows, &c.name) {
                     Ok(Transformed::yes(unproj.clone()))
                 } else {
                     Ok(Transformed::no(Expr::Column(c)))
@@ -127,3 +157,21 @@ pub(crate) fn unproject_window_exprs(expr: &Expr, windows: &[&Window]) -> Result
         })
         .map(|e| e.data)
 }
+
+fn find_agg_expr<'a>(agg: &'a Aggregate, column: &Column) -> Option<&'a Expr> {
+    if let Ok(index) = agg.schema.index_of_column(column) {
+        agg.group_expr.iter().chain(agg.aggr_expr.iter()).nth(index)
+    } else {
+        None
+    }
+}
+
+fn find_window_expr<'a>(
+    windows: &'a [&'a Window],
+    column_name: &'a str,
+) -> Option<&'a Expr> {
+    windows
+        .iter()
+        .flat_map(|w| w.window_expr.iter())
+        .find(|expr| expr.schema_name().to_string() == column_name)
+}

datafusion/sql/tests/cases/plan_to_sql.rs

@@ -146,6 +146,11 @@ fn roundtrip_statement() -> Result<()> {
             sum(id) OVER (PARTITION BY first_name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) from person"#,
             "SELECT id, sum(id) OVER (PARTITION BY first_name ROWS BETWEEN 5 PRECEDING AND 2 FOLLOWING) from person",
             "WITH t1 AS (SELECT j1_id AS id, j1_string name FROM j1), t2 AS (SELECT j2_id AS id, j2_string name FROM j2) SELECT * FROM t1 JOIN t2 USING (id, name)",
+            r#"SELECT id, first_name,
+            SUM(id) AS total_sum,
+            SUM(id) OVER (PARTITION BY first_name ROWS BETWEEN 5 PRECEDING AND 2 FOLLOWING) AS moving_sum,
+            MAX(SUM(id)) OVER (PARTITION BY first_name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS max_total
+            FROM person GROUP BY id, first_name"#,
         ];
 
     // For each test sql string, we transform as follows:
@@ -161,6 +166,7 @@ fn roundtrip_statement() -> Result<()> {
         let state = MockSessionState::default()
             .with_aggregate_function(sum_udaf())
             .with_aggregate_function(count_udaf())
+            .with_aggregate_function(max_udaf())
             .with_expr_planner(Arc::new(CoreFunctionPlanner::default()));
         let context = MockContextProvider { state };
         let sql_to_rel = SqlToRel::new(&context);