From f50decafc33b2f5aba9bca15e5077617f47c8ede Mon Sep 17 00:00:00 2001
From: Daniel Widgren <daniel.widgren@gmail.com>
Date: Fri, 13 Mar 2026 09:32:24 +0100
Subject: [PATCH] fix: return query_timeout instead of closed on deadline

When a pool deadline fires during query execution, the socket is
closed and recv returns {error, closed}. This is indistinguishable
from actual connection failures. Now detect deadline-triggered
disconnects by checking if the holder ETS table was deleted, and
return {error, query_timeout} instead.

Closes #96
---
 src/pgo.erl        | 15 ++++++++++++++-
 test/pgo_SUITE.erl | 15 +++++++++++++--
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/pgo.erl b/src/pgo.erl
index d08a259..267edf0 100644
--- a/src/pgo.erl
+++ b/src/pgo.erl
@@ -101,9 +101,16 @@ query(Query, Params, Options) ->
             Pool = maps:get(pool, Options, default),
             PoolOptions = maps:get(pool_options, Options, []),
             case checkout(Pool, PoolOptions) of
-                {ok, Ref, Conn} ->
+                {ok, Ref={_, _, _, Holder}, Conn} ->
                     try
                         query(Query, Params, Options, Conn)
+                    of
+                        {error, closed} ->
+                            maybe_timeout_error(Holder);
+                        {error, einval} ->
+                            maybe_timeout_error(Holder);
+                        Result ->
+                            Result
                     after
                         checkin(Ref, Conn)
                     end;
@@ -230,6 +237,12 @@ checkin(Ref, Conn) ->
 break(Conn) ->
     pgo_connection:break(Conn).
 
+maybe_timeout_error(Holder) ->
+    case ets:info(Holder, size) of
+        undefined -> {error, query_timeout};
+        _ -> {error, closed}
+    end.
+
 format_error(Error=#{module := Module}) ->
     Module:format_error(Error);
 format_error(Error) ->
diff --git a/test/pgo_SUITE.erl b/test/pgo_SUITE.erl
index e12c634..2bfe863 100644
--- a/test/pgo_SUITE.erl
+++ b/test/pgo_SUITE.erl
@@ -15,7 +15,8 @@
                        Until(I) -> case X of true -> ok; false -> timer:sleep(10), Until(I+1) end end)(0)).
 
 all() -> [checkout_checkin, checkout_break, recheckout, kill_socket, kill_pid,
-          checkout_kill, checkout_disconnect, checkout_query_crash].
+          checkout_kill, checkout_disconnect, checkout_query_crash,
+          query_timeout].
 
 init_per_suite(Config) ->
     Config.
@@ -27,7 +28,8 @@ init_per_testcase(T, Config) when T =:= checkout_break ;
                                   T =:= checkout_query_crash ;
                                   T =:= recheckout ;
                                   T =:= kill_socket ;
-                                  T =:= kill_pid ->
+                                  T =:= kill_pid ;
+                                  T =:= query_timeout ->
     Pool = list_to_atom("pool_" ++ atom_to_list(T)),
     application:ensure_all_started(pgo),
     pgo_sup:start_child(Pool, #{pool_size => 1,
@@ -242,3 +244,12 @@ checkout_query_crash(Config) ->
                          end),
 
     ok.
+
+query_timeout(Config) ->
+    Name = ?config(pool_name, Config),
+    %% Use a very short deadline so the query times out
+    Result = pgo:query("SELECT pg_sleep(5)", [],
+                       #{pool => Name,
+                         pool_options => [{timeout, 500}]}),
+    ?assertEqual({error, query_timeout}, Result),
+    ok.