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CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [0.6.0] - 2023-12-18
 ### Added
 - Unsupported DP aggregations are handled gracefully
+- Rewrite into DP Reduce with MAX, MIN, QUANTILE(S), FIRST, LAST, MEDIAN if they are applied on a grouping column [#227](https://github.com/Qrlew/qrlew/issues/227)
 
 ## [0.5.6] - 2023-12-18
 ### Fixed

src/differential_privacy/aggregates.rs

@@ -3,10 +3,10 @@ use crate::{
     data_type::DataTyped,
     differential_privacy::private_query::PrivateQuery,
     differential_privacy::{private_query, DPRelation, Error, Result},
-    expr::{aggregate, AggregateColumn, Expr, Column, Identifier},
+    expr::{aggregate::{self, Aggregate}, AggregateColumn, Expr, Column, Identifier},
     privacy_unit_tracking::PUPRelation,
     relation::{field::Field, Map, Reduce, Relation, Variant},
-    DataType, Ready, display::Dot,
+    DataType, Ready,
 
 };
 use std::{cmp, collections::HashMap, ops::Deref};
@@ -161,10 +161,16 @@ impl PUPRelation {
                 let square_col = format!("_SQUARE_{}", col_name);
                 let sum_square_col = format!("_SUM_{}", square_col);
                 match aggregate.aggregate() {
-                    aggregate::Aggregate::First => {
+                    Aggregate::Min |
+                    Aggregate::Max |
+                    Aggregate::Median |
+                    Aggregate::First |
+                    Aggregate::Last |
+                    Aggregate::Quantile(_) |
+                    Aggregate::Quantiles(_) => {
                         assert!(group_by_names.contains(&col_name.as_str()));
                         output_b = output_b.with((name, Expr::col(col_name.as_str())))
-                    }
+                    },
                     aggregate::Aggregate::Mean => {
                         input_b = input_b
                             .with((col_name.as_str(), Expr::col(col_name.as_str())))

src/differential_privacy/mod.rs

@@ -13,7 +13,8 @@ use crate::{
     differential_privacy::private_query::PrivateQuery,
     expr, privacy_unit_tracking,
     relation::{rewriting, Reduce, Relation},
-    Ready, data_type::function::Aggregate,
+    Ready,
+    display::Dot
 };
 use std::{error, fmt, ops::Deref, result};
 
@@ -177,7 +178,7 @@ mod tests {
         io::{postgresql, Database},
         privacy_unit_tracking::PrivacyUnit,
         privacy_unit_tracking::{PrivacyUnitTracking, Strategy},
-        relation::{Field, Map, Relation, Schema, Variant},
+        relation::{Field, Map, Relation, Schema, Variant, Constraint},
     };
     use std::collections::HashSet;
 
@@ -620,4 +621,67 @@ mod tests {
             .collect();
         assert_eq!(city_keys, correct_keys);
     }
+
+    #[test]
+    fn test_dp_rewrite_reduce() {
+        let mut database = postgresql::test_database();
+        let relations = database.relations();
+
+        let table = relations
+            .get(&["table_1".to_string()])
+            .unwrap()
+            .deref()
+            .clone();
+        let (epsilon, delta) = (1., 1e-3);
+        let (epsilon_tau_thresholding, delta_tau_thresholding) = (0.5, 2e-3);
+
+        // privacy track the inputs
+        let privacy_unit_tracking = PrivacyUnitTracking::from((
+            &relations,
+            vec![("table_1", vec![], PrivacyUnit::privacy_unit_row())],
+            Strategy::Hard,
+        ));
+        let pup_table = privacy_unit_tracking
+            .table(&table.try_into().unwrap())
+            .unwrap();
+        let reduce = Reduce::new(
+            "my_reduce".to_string(),
+            vec![
+                ("sum_a".to_string(), AggregateColumn::sum("a")),
+                ("d".to_string(), AggregateColumn::first("d")),
+                ("max_d".to_string(), AggregateColumn::max("d")),
+            ],
+            vec!["d".into()],
+            pup_table.deref().clone().into(),
+        );
+        let relation = Relation::from(reduce.clone());
+        relation.display_dot().unwrap();
+
+        let (dp_relation, private_query) = reduce
+            .differentially_private(
+                epsilon,
+                delta,
+                epsilon_tau_thresholding,
+                delta_tau_thresholding,
+            )
+            .unwrap()
+            .into();
+        dp_relation.display_dot().unwrap();
+        assert_eq!(
+            private_query,
+            PrivateQuery::EpsilonDelta(epsilon_tau_thresholding, delta_tau_thresholding)
+                .compose(PrivateQuery::gaussian_from_epsilon_delta_sensitivity(epsilon, delta, 10.))
+        );
+        let correct_schema: Schema = vec![
+            ("sum_a", DataType::float_interval(0., 100.), None),
+            ("d", DataType::integer_interval(0, 10), Some(Constraint::Unique)),
+            ("max_d", DataType::integer_interval(0, 10), Some(Constraint::Unique)),
+        ].into_iter()
+        .collect();
+        assert_eq!(dp_relation.schema(), &correct_schema);
+
+        let query: &str = &ast::Query::from(&dp_relation).to_string();
+        println!("{query}");
+        _ = database.query(query).unwrap();
+    }
 }

src/rewriting/mod.rs

@@ -187,6 +187,7 @@ mod tests {
             "SELECT order_id, sum(price), sum(distinct price) FROM item_table GROUP BY order_id HAVING count(*) > 2",
             "SELECT order_id, sum(order_id) FROM item_table GROUP BY order_id",
             "SELECT order_id As my_order, sum(price) FROM item_table GROUP BY my_order",
+            "SELECT order_id, MAX(order_id), sum(price) FROM item_table GROUP BY order_id"
         ];
 
         for q in queries {

src/rewriting/rewriting_rule.rs

@@ -706,7 +706,7 @@ impl<'a> SetRewritingRulesVisitor<'a> for RewritingRulesSetter<'a> {
                 Aggregate::Quantile(_) |
                 Aggregate::Quantiles(_) => reduce.group_by().contains(f.column()),
                 _ => false,
-                
+
             }
         }) {
             rewriting_rules.push(