LATERAL subquery support

Author: WillAbides

internal/compiler/output_columns.go

@@ -592,7 +592,24 @@ func (c *Compiler) sourceTables(qc *QueryCatalog, node ast.Node) ([]*Table, erro
 			tables = append(tables, table)
 
 		case *ast.RangeSubselect:
-			cols, err := c.outputColumns(qc, n.Subquery)
+			lateralQC := qc
+			if n.Lateral && len(tables) > 0 {
+				// LATERAL allows the subquery to reference columns from preceding FROM items.
+				lateralTables := make(map[string]*Table, len(tables))
+				for _, table := range tables {
+					if table.Rel != nil && table.Rel.Name != "" {
+						lateralTables[table.Rel.Name] = table
+					}
+				}
+				lateralQC = &QueryCatalog{
+					catalog:       qc.catalog,
+					ctes:          qc.ctes,
+					embeds:        qc.embeds,
+					lateralTables: lateralTables,
+				}
+			}
+
+			cols, err := c.outputColumns(lateralQC, n.Subquery)
 			if err != nil {
 				return nil, err
 			}
@@ -637,6 +654,15 @@ func (c *Compiler) sourceTables(qc *QueryCatalog, node ast.Node) ([]*Table, erro
 			return nil, fmt.Errorf("sourceTable: unsupported list item type: %T", n)
 		}
 	}
+
+	// Add LATERAL outer tables to the tables list.
+	// LATERAL subqueries can reference these outer tables for column resolution.
+	if qc != nil {
+		for _, lateralTable := range qc.lateralTables {
+			tables = append(tables, lateralTable)
+		}
+	}
+
 	return tables, nil
 }
 

internal/compiler/query_catalog.go

@@ -12,6 +12,8 @@ type QueryCatalog struct {
 	catalog *catalog.Catalog
 	ctes    map[string]*Table
 	embeds  rewrite.EmbedSet
+
+	lateralTables map[string]*Table
 }
 
 func (comp *Compiler) buildQueryCatalog(c *catalog.Catalog, node ast.Node, embeds rewrite.EmbedSet) (*QueryCatalog, error) {

internal/endtoend/testdata/lateral_view_column_ref/issue.md

@@ -0,0 +1,3 @@
+https://github.com/sqlc-dev/sqlc/issues/4182
+
+LATERAL subquery column references from outer query fail with "column does not exist".

internal/endtoend/testdata/lateral_view_column_ref/postgresql/pgx/go/db.go

@@ -0,0 +1,9 @@
+-- name: GetFooLateral :many
+SELECT val, result FROM foo_lateral;
+
+-- name: GetFooLateralDirect :many
+SELECT f.id, f.val, sub.result
+FROM foo f
+CROSS JOIN LATERAL (
+  SELECT f.val || '-direct' AS result
+) sub;

internal/endtoend/testdata/lateral_view_column_ref/postgresql/pgx/go/models.go

@@ -0,0 +1,13 @@
+CREATE TABLE foo (
+  id integer PRIMARY KEY,
+  val text NOT NULL
+);
+
+-- Reproduces issue #4182: LATERAL subquery referencing outer column
+CREATE VIEW foo_lateral AS
+SELECT t.val, sub.result
+FROM foo t
+CROSS JOIN LATERAL (
+  SELECT t.val AS result
+  FROM foo LIMIT 1
+) sub;

internal/endtoend/testdata/lateral_view_column_ref/postgresql/pgx/go/query.sql.go

@@ -0,0 +1,10 @@
+version: "2"
+sql:
+  - engine: "postgresql"
+    schema: "schema.sql"
+    queries: "query.sql"
+    gen:
+      go:
+        package: "querytest"
+        out: "go"
+        sql_package: "pgx/v5"