fix: Show more detailed error when table not found

lib/logflare_web/controllers/endpoints_controller.ex

@@ -2,6 +2,8 @@ defmodule LogflareWeb.EndpointsController do
   use LogflareWeb, :controller
   use OpenApiSpex.ControllerSpecs
 
+  import Logflare.Utils.Guards, only: [is_non_empty_binary: 1]
+
   require Logger
 
   alias Logflare.Backends.QueryError
@@ -97,6 +99,9 @@ defmodule LogflareWeb.EndpointsController do
       {:error, error = %QueryError{}} ->
         render(conn, "query.json", error: QueryErrorHelpers.query_error_message(error))
 
+      {:error, message} when is_non_empty_binary(message) ->
+        render(conn, "query.json", error: QueryErrorHelpers.sandbox_query_error_message(message))
+
       {:error, _errors} ->
         render(conn, "query.json", error: QueryErrorHelpers.generic_query_error_message())
     end

lib/logflare_web/query_error_helpers.ex

@@ -50,6 +50,43 @@ defmodule LogflareWeb.QueryErrorHelpers do
   @spec generic_query_error_message() :: String.t()
   def generic_query_error_message, do: @generic_query_error_message
 
+  @doc """
+  Returns a user-facing message for a sandboxed-query validation error, as
+  returned by `Logflare.Endpoints.run_query/3` when the query fails validation
+  before ever reaching a backend.
+
+  Only the "unknown table" case is translated into a plain message; anything
+  else falls back to the generic message, since Logflare's internal CTE
+  splicing would otherwise leak into a user-facing error and confuse callers
+  who never wrote a CTE themselves.
+
+      iex> LogflareWeb.QueryErrorHelpers.sandbox_query_error_message("Table not found in CTE: (function_logs)")
+      ~s(Table "function_logs" does not exist.)
+
+      iex> LogflareWeb.QueryErrorHelpers.sandbox_query_error_message("Multiple CTEs available (first_cte, second_cte). You must specify which one to query using `f:name`")
+      "Backend error! Retry your query. Please contact support if this continues."
+
+      iex> LogflareWeb.QueryErrorHelpers.sandbox_query_error_message("sql parser error: Expected: SELECT, VALUES, or a subquery in the query body, found: EOF")
+      "Backend error! Retry your query. Please contact support if this continues."
+  """
+  @spec sandbox_query_error_message(String.t()) :: String.t()
+  def sandbox_query_error_message(message) when is_binary(message) do
+    classified_sandbox_error_message(message) || generic_query_error_message()
+  end
+
+  defp classified_sandbox_error_message("Table not found in CTE: (" <> rest) do
+    rest |> String.trim_trailing(")") |> unknown_table_message()
+  end
+
+  defp classified_sandbox_error_message(_message), do: nil
+
+  defp unknown_table_message(names) do
+    case String.split(names, ", ") do
+      [single] -> ~s(Table "#{single}" does not exist.)
+      multiple -> "Tables #{Enum.map_join(multiple, ", ", &~s("#{&1}"))} do not exist."
+    end
+  end
+
   @doc """
   Whether a backend %QueryError{} was caused by a query timeout.
 

test/logflare_web/controllers/endpoints_controller_test.exs

@@ -257,8 +257,7 @@ defmodule LogflareWeb.EndpointsControllerTest do
         conn
         |> json_response(200)
 
-      assert response["error"] =~
-               LogflareWeb.QueryErrorHelpers.generic_query_error_message()
+      assert response["error"] == LogflareWeb.QueryErrorHelpers.generic_query_error_message()
 
       refute response["result"]
     end
@@ -376,8 +375,7 @@ defmodule LogflareWeb.EndpointsControllerTest do
         conn
         |> json_response(200)
 
-      assert response["error"] =~
-               LogflareWeb.QueryErrorHelpers.generic_query_error_message()
+      assert response["error"] == LogflareWeb.QueryErrorHelpers.generic_query_error_message()
 
       refute response["result"]
     end
@@ -503,6 +501,33 @@ defmodule LogflareWeb.EndpointsControllerTest do
       assert String.downcase(sql) =~ "select 2"
     end
 
+    test "sql referencing a table not in the endpoint's CTE returns a specific error", %{
+      conn: conn,
+      user: user
+    } do
+      reject(&BigQueryJobs.bigquery_jobs_query/3)
+
+      backend = insert(:backend, type: :clickhouse, user: user)
+
+      endpoint =
+        insert(:endpoint,
+          user: user,
+          backend: backend,
+          language: :ch_sql,
+          enable_auth: true,
+          sandboxable: true,
+          query: "with a as (select 1 as b) select b from a"
+        )
+
+      conn =
+        conn
+        |> put_req_header("x-api-key", user.api_key)
+        |> get(~p"/api/endpoints/query/#{endpoint.name}", %{sql: "select b from function_logs"})
+
+      assert json_response(conn, 200)["error"] == ~s(Table "function_logs" does not exist.)
+      refute json_response(conn, 200)["result"]
+    end
+
     test "LQL params in GET query string", %{conn: conn, user: user} do
       pid = self()