fix: revert sorts on all CTEs (in PQ postprocessing) (#5128)

prqlc/prqlc/src/sql/pq/postprocess.rs

@@ -95,7 +95,6 @@ impl PqMapper<RelationExpr, RelationExpr, (), ()> for SortingInference<'_> {
         transforms: Vec<SqlTransform<RelationExpr, ()>>,
     ) -> Result<Vec<SqlTransform<RelationExpr, ()>>> {
         let mut sorting = Vec::new();
-        let mut has_sort_transform = false;
 
         let mut result = Vec::with_capacity(transforms.len() + 1);
 
@@ -128,7 +127,6 @@ impl PqMapper<RelationExpr, RelationExpr, (), ()> for SortingInference<'_> {
                 // just store sorting and don't emit Sort
                 SqlTransform::Sort(expr) => {
                     sorting.clone_from(&expr);
-                    has_sort_transform = true;
                     continue;
                 }
 
@@ -159,13 +157,11 @@ impl PqMapper<RelationExpr, RelationExpr, (), ()> for SortingInference<'_> {
                 }
             }
 
-            if has_sort_transform {
-                // now revert the sort columns so that the output
-                // sorting reflects the input column cids, needed to
-                // ensure proper column reference lookup in the final
-                // steps
-                sorting = CidRedirector::revert_sorts(sorting, &mut self.ctx.anchor);
-            }
+            // now revert the sort columns so that the output
+            // sorting reflects the input column cids, needed to
+            // ensure proper column reference lookup in the final
+            // steps
+            sorting = CidRedirector::revert_sorts(sorting, &mut self.ctx.anchor);
         }
 
         // remember sorting for this pipeline

prqlc/prqlc/tests/integration/queries/sort_3.prql

@@ -0,0 +1,8 @@
+from [{track_id=0, album_id=1, genre_id=2}]
+select { AA=track_id, album_id, genre_id }
+sort AA
+join side:left [{album_id=1, album_title="Songs"}] (==album_id)
+select { AA, AT = album_title ?? "unknown", genre_id }
+filter AA < 25
+join side:left [{genre_id=1, genre_title="Rock"}] (==genre_id)
+select { AA, AT, GT = genre_title ?? "unknown" }

prqlc/prqlc/tests/integration/snapshots/integration__queries__compile__sort_3.snap

@@ -0,0 +1,57 @@
+---
+source: prqlc/prqlc/tests/integration/queries.rs
+expression: "from [{track_id=0, album_id=1, genre_id=2}]\nselect { AA=track_id, album_id, genre_id }\nsort AA\njoin side:left [{album_id=1, album_title=\"Songs\"}] (==album_id)\nselect { AA, AT = album_title ?? \"unknown\", genre_id }\nfilter AA < 25\njoin side:left [{genre_id=1, genre_title=\"Rock\"}] (==genre_id)\nselect { AA, AT, GT = genre_title ?? \"unknown\" }\n"
+input_file: prqlc/prqlc/tests/integration/queries/sort_3.prql
+---
+WITH table_0 AS (
+  SELECT
+    0 AS track_id,
+    1 AS album_id,
+    2 AS genre_id
+),
+table_5 AS (
+  SELECT
+    track_id AS "AA",
+    genre_id,
+    album_id
+  FROM
+    table_0
+),
+table_1 AS (
+  SELECT
+    1 AS album_id,
+    'Songs' AS album_title
+),
+table_4 AS (
+  SELECT
+    table_5."AA",
+    COALESCE(table_1.album_title, 'unknown') AS "AT",
+    table_5.genre_id
+  FROM
+    table_5
+    LEFT JOIN table_1 ON table_5.album_id = table_1.album_id
+),
+table_3 AS (
+  SELECT
+    "AA",
+    "AT",
+    genre_id
+  FROM
+    table_4
+  WHERE
+    "AA" < 25
+),
+table_2 AS (
+  SELECT
+    1 AS genre_id,
+    'Rock' AS genre_title
+)
+SELECT
+  table_3."AA",
+  table_3."AT",
+  COALESCE(table_2.genre_title, 'unknown') AS "GT"
+FROM
+  table_3
+  LEFT JOIN table_2 ON table_3.genre_id = table_2.genre_id
+ORDER BY
+  table_3."AA"