QueryRewriter.RewriteQuery now returns an error

https://github.com/jackc/pgx/issues/1186#issuecomment-1288207250

conn.go

@@ -407,7 +407,10 @@ optionLoop:
 	}
 
 	if queryRewriter != nil {
-		sql, arguments = queryRewriter.RewriteQuery(ctx, c, sql, arguments)
+		sql, arguments, err = queryRewriter.RewriteQuery(ctx, c, sql, arguments)
+		if err != nil {
+			return pgconn.CommandTag{}, fmt.Errorf("rewrite query failed: %v", err)
+		}
 	}
 
 	// Always use simple protocol when there are no arguments.
@@ -600,7 +603,7 @@ type QueryResultFormatsByOID map[uint32]int16
 
 // QueryRewriter rewrites a query when used as the first arguments to a query method.
 type QueryRewriter interface {
-	RewriteQuery(ctx context.Context, conn *Conn, sql string, args []any) (newSQL string, newArgs []any)
+	RewriteQuery(ctx context.Context, conn *Conn, sql string, args []any) (newSQL string, newArgs []any, err error)
 }
 
 // Query sends a query to the server and returns a Rows to read the results. Only errors encountered sending the query
@@ -659,7 +662,16 @@ optionLoop:
 	}
 
 	if queryRewriter != nil {
-		sql, args = queryRewriter.RewriteQuery(ctx, c, sql, args)
+		var err error
+		originalSQL := sql
+		originalArgs := args
+		sql, args, err = queryRewriter.RewriteQuery(ctx, c, sql, args)
+		if err != nil {
+			rows := c.getRows(ctx, originalSQL, originalArgs)
+			err = fmt.Errorf("rewrite query failed: %v", err)
+			rows.fatal(err)
+			return rows, err
+		}
 	}
 
 	// Bypass any statement caching.
@@ -826,7 +838,11 @@ func (c *Conn) SendBatch(ctx context.Context, b *Batch) (br BatchResults) {
 		}
 
 		if queryRewriter != nil {
-			sql, arguments = queryRewriter.RewriteQuery(ctx, c, sql, arguments)
+			var err error
+			sql, arguments, err = queryRewriter.RewriteQuery(ctx, c, sql, arguments)
+			if err != nil {
+				return &batchResults{ctx: ctx, conn: c, err: fmt.Errorf("rewrite query failed: %v", err)}
+			}
 		}
 
 		bi.query = sql

conn_test.go

@@ -236,8 +236,8 @@ type testQueryRewriter struct {
 	args []any
 }
 
-func (qr *testQueryRewriter) RewriteQuery(ctx context.Context, conn *pgx.Conn, sql string, args []any) (newSQL string, newArgs []any) {
-	return qr.sql, qr.args
+func (qr *testQueryRewriter) RewriteQuery(ctx context.Context, conn *pgx.Conn, sql string, args []any) (newSQL string, newArgs []any, err error) {
+	return qr.sql, qr.args, nil
 }
 
 func TestExecWithQueryRewriter(t *testing.T) {

named_args.go

@@ -12,12 +12,12 @@ import (
 //
 // For example, the following two queries are equivalent:
 //
-// 	conn.Query(ctx, "select * from widgets where foo = @foo and bar = @bar", pgx.NamedArgs{"foo": 1, "bar": 2})
-// 	conn.Query(ctx, "select * from widgets where foo = $1 and bar = $2", 1, 2)
+//	conn.Query(ctx, "select * from widgets where foo = @foo and bar = @bar", pgx.NamedArgs{"foo": 1, "bar": 2})
+//	conn.Query(ctx, "select * from widgets where foo = $1 and bar = $2", 1, 2)
 type NamedArgs map[string]any
 
 // RewriteQuery implements the QueryRewriter interface.
-func (na NamedArgs) RewriteQuery(ctx context.Context, conn *Conn, sql string, args []any) (newSQL string, newArgs []any) {
+func (na NamedArgs) RewriteQuery(ctx context.Context, conn *Conn, sql string, args []any) (newSQL string, newArgs []any, err error) {
 	l := &sqlLexer{
 		src:           sql,
 		stateFn:       rawState,
@@ -44,7 +44,7 @@ func (na NamedArgs) RewriteQuery(ctx context.Context, conn *Conn, sql string, ar
 		newArgs[ordinal-1] = na[string(name)]
 	}
 
-	return sb.String(), newArgs
+	return sb.String(), newArgs, nil
 }
 
 type namedArg string

named_args_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/jackc/pgx/v5"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestNamedArgsRewriteQuery(t *testing.T) {
@@ -95,7 +96,8 @@ func TestNamedArgsRewriteQuery(t *testing.T) {
 
 		// test comments and quotes
 	} {
-		sql, args := tt.namedArgs.RewriteQuery(context.Background(), nil, tt.sql, tt.args)
+		sql, args, err := tt.namedArgs.RewriteQuery(context.Background(), nil, tt.sql, tt.args)
+		require.NoError(t, err)
 		assert.Equalf(t, tt.expectedSQL, sql, "%d", i)
 		assert.Equalf(t, tt.expectedArgs, args, "%d", i)
 	}