fix(dolphin): preserve NOT EXISTS expressions

internal/engine/dolphin/convert.go

@@ -397,13 +397,22 @@ func (c *cc) convertRenameTableStmt(n *pcast.RenameTableStmt) ast.Node {
 	return list
 }
 
-func (c *cc) convertExistsSubqueryExpr(n *pcast.ExistsSubqueryExpr) *ast.SubLink {
+func (c *cc) convertExistsSubqueryExpr(n *pcast.ExistsSubqueryExpr) ast.Node {
 	sublink := &ast.SubLink{
 		SubLinkType: ast.EXISTS_SUBLINK,
 	}
 	if n.Sel != nil {
 		sublink.Subselect = c.convert(n.Sel)
 	}
+	if n.Not {
+		return &ast.BoolExpr{
+			Boolop: ast.BoolExprTypeNot,
+			Args: &ast.List{
+				Items: []ast.Node{sublink},
+			},
+			Location: n.OriginTextPosition(),
+		}
+	}
 	return sublink
 }
 
@@ -1556,6 +1565,15 @@ func (c *cc) convertTruncateTableStmt(n *pcast.TruncateTableStmt) *ast.TruncateS
 }
 
 func (c *cc) convertUnaryOperationExpr(n *pcast.UnaryOperationExpr) ast.Node {
+	if n.Op == opcode.Not {
+		return &ast.BoolExpr{
+			Boolop: ast.BoolExprTypeNot,
+			Args: &ast.List{
+				Items: []ast.Node{c.convert(n.V)},
+			},
+			Location: n.OriginTextPosition(),
+		}
+	}
 	return todo(n)
 }
 

internal/engine/dolphin/convert_test.go

@@ -0,0 +1,60 @@
+package dolphin
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/sqlc-dev/sqlc/internal/sql/ast"
+)
+
+func TestConvertNotExistsSubquery(t *testing.T) {
+	const query = `UPDATE target_table
+SET active = 0
+WHERE NOT (
+    EXISTS (
+        SELECT 1
+        FROM source_table s
+        WHERE s.updated_at >= sqlc.arg(updated_after)
+    )
+)`
+
+	parser := NewParser()
+	stmts, err := parser.Parse(strings.NewReader(query))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(stmts) != 1 {
+		t.Fatalf("expected one statement, got %d", len(stmts))
+	}
+
+	formatted := ast.Format(stmts[0].Raw, parser)
+	if !strings.Contains(formatted, "NOT EXISTS") {
+		t.Errorf("expected NOT EXISTS to be preserved, got:\n%s", formatted)
+	}
+	if !strings.Contains(formatted, "sqlc.arg(updated_after)") {
+		t.Errorf("expected named parameter to be preserved, got:\n%s", formatted)
+	}
+}
+
+func TestConvertNotExistsSubqueryWithoutParentheses(t *testing.T) {
+	const query = `SELECT 1
+WHERE NOT EXISTS (
+    SELECT 1
+    FROM source_table s
+    WHERE s.updated_at >= sqlc.arg(updated_after)
+)`
+
+	parser := NewParser()
+	stmts, err := parser.Parse(strings.NewReader(query))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(stmts) != 1 {
+		t.Fatalf("expected one statement, got %d", len(stmts))
+	}
+
+	formatted := ast.Format(stmts[0].Raw, parser)
+	if !strings.Contains(formatted, "NOT EXISTS") {
+		t.Errorf("expected NOT EXISTS to be preserved, got:\n%s", formatted)
+	}
+}