sql: fix scope tracking when planning joins

src/sql/planner/planner.rs

@@ -277,29 +277,29 @@ impl<'a, C: Catalog> Planner<'a, C> {
 
         // Build and implicitly join additional items.
         for from in items {
-            // Each item is evaluated in its own, initially empty scope, and
-            // can't reference previous items. Consider e.g. "SELECT * FROM a,
-            // b JOIN c ON c.id = a.id" which is illegal (the join predicate can
-            // reference b or c, but not a).
-            let mut right_scope = Scope::new();
-            let right = self.build_from(from, &mut right_scope)?;
+            let left_size = scope.len();
+            let right = self.build_from(from, scope)?;
+            let right_size = scope.len() - left_size;
             node = Node::NestedLoopJoin {
                 left: Box::new(node),
-                left_size: scope.len(),
+                left_size,
                 right: Box::new(right),
-                right_size: right_scope.len(),
+                right_size,
                 predicate: None,
                 outer: false,
             };
-            scope.merge(right_scope)?;
         }
         Ok(node)
     }
 
     /// Builds FROM items, which can either be a single table or a chained join
     /// of multiple tables, e.g. "SELECT * FROM a LEFT JOIN b ON b.a_id = a.id".
-    fn build_from(&self, from: ast::From, scope: &mut Scope) -> Result<Node> {
-        Ok(match from {
+    fn build_from(&self, from: ast::From, parent_scope: &mut Scope) -> Result<Node> {
+        // Each from item is built in its own scope, such that a join node only
+        // sees the columns of its children. It's then merged into the parent.
+        let mut scope = Scope::new();
+
+        let node = match from {
             // A full table scan.
             ast::From::Table { name, alias } => {
                 let table = self.catalog.must_get_table(&name)?;
@@ -316,13 +316,13 @@ impl<'a, C: Catalog> Planner<'a, C> {
                 }
 
                 // Build the left and right nodes.
-                let left = Box::new(self.build_from(*left, scope)?);
+                let left = Box::new(self.build_from(*left, &mut scope)?);
                 let left_size = scope.len();
-                let right = Box::new(self.build_from(*right, scope)?);
+                let right = Box::new(self.build_from(*right, &mut scope)?);
                 let right_size = scope.len() - left_size;
 
-                //  Build the join node.
-                let predicate = predicate.map(|e| Self::build_expression(e, scope)).transpose()?;
+                // Build the join node.
+                let predicate = predicate.map(|e| Self::build_expression(e, &scope)).transpose()?;
                 let outer = r#type.is_outer();
                 let mut node =
                     Node::NestedLoopJoin { left, left_size, right, right_size, predicate, outer };
@@ -339,7 +339,10 @@ impl<'a, C: Catalog> Planner<'a, C> {
                 }
                 node
             }
-        })
+        };
+
+        parent_scope.merge(scope)?;
+        Ok(node)
     }
 
     /// Builds an aggregation node. All aggregate parameters and GROUP BY expressions are evaluated

src/sql/testscripts/queries/join_outer

@@ -160,12 +160,26 @@ NestedLoopJoin: outer on genres.id > movies.id OR genres.id = movies.id
 10, Inception, 4, 1, 2010, 8.8, TRUE, NULL, NULL
 
 # Three-way join.
-# TODO: this shouldn't panic.
-[plan]!> SELECT * FROM studios \
+[plan]> SELECT * FROM studios \
     LEFT JOIN genres ON studios.id = genres.id \
     RIGHT JOIN movies ON movies.id = studios.id
 ---
-Panic: index out of bounds: the len is 3 but the index is 7
+Projection: studios.id, studios.name, studios.country_id, genres.id, genres.name, movies.id, movies.title, movies.studio_id, movies.genre_id, movies.released, movies.rating, movies.ultrahd
+└─ HashJoin: outer on movies.id = studios.id
+   ├─ Scan: movies
+   └─ HashJoin: outer on studios.id = genres.id
+      ├─ Scan: studios
+      └─ Scan: genres
+1, Mosfilm, ru, 1, Science Fiction, 1, Stalker, 1, 1, 1979, 8.2, NULL
+2, Lionsgate, us, 2, Action, 2, Sicario, 2, 2, 2015, 7.6, TRUE
+3, StudioCanal, fr, 3, Comedy, 3, Primer, 3, 1, 2004, 6.9, NULL
+4, Warner Bros, us, NULL, NULL, 4, Heat, 4, 2, 1995, 8.2, TRUE
+NULL, NULL, NULL, NULL, NULL, 5, The Fountain, 4, 1, 2006, 7.2, FALSE
+NULL, NULL, NULL, NULL, NULL, 6, Solaris, 1, 1, 1972, 8.1, NULL
+NULL, NULL, NULL, NULL, NULL, 7, Gravity, 4, 1, 2013, 7.7, TRUE
+NULL, NULL, NULL, NULL, NULL, 8, Blindspotting, 2, 3, 2018, 7.4, TRUE
+NULL, NULL, NULL, NULL, NULL, 9, Birdman, 4, 3, 2014, 7.7, TRUE
+NULL, NULL, NULL, NULL, NULL, 10, Inception, 4, 1, 2010, 8.8, TRUE
 
 # Aliased tables.
 [plan]> SELECT * FROM movies m LEFT JOIN genres AS g on m.id = g.id