From e2a69ee5f96f64ea94f62f9085591129899b3b7c Mon Sep 17 00:00:00 2001 From: Jacob Champion Date: Mon, 23 Feb 2026 15:28:32 -0800 Subject: [PATCH v2] pg_upgrade: Use max_protocol_version=3.0 for older servers The grease patch in 4966bd3ed found its first problem: prior to the February 2018 patch releases, no server knew how to negotiate protocol versions, so pg_upgrade needs to take that into account when speaking to those older servers. This will be true even after the grease feature is reverted; we don't need anyone to trip over this again in the future. Backpatch so that all supported versions of pg_upgrade can gracefully handle an update to the default protocol version. (This is needed for any distributions that link older binaries against newer libpqs, such as Debian.) Branches prior to 18 need an additional version check, for the existence of max_protocol_version. Per buildfarm member crake. Discussion: https://postgr.es/m/CAOYmi%2B%3D4QhCjssfNEoZVK8LPtWxnfkwT5p-PAeoxtG9gpNjqOQ%40mail.gmail.com Backpatch-through: 14 --- src/bin/pg_upgrade/pg_upgrade.h | 1 + src/bin/pg_upgrade/dump.c | 6 +++++- src/bin/pg_upgrade/server.c | 2 ++ src/bin/pg_upgrade/task.c | 2 ++ src/bin/pg_upgrade/version.c | 18 ++++++++++++++++++ 5 files changed, 28 insertions(+), 1 deletion(-) diff --git a/src/bin/pg_upgrade/pg_upgrade.h b/src/bin/pg_upgrade/pg_upgrade.h index ec018e4f292..1d767bbda2d 100644 --- a/src/bin/pg_upgrade/pg_upgrade.h +++ b/src/bin/pg_upgrade/pg_upgrade.h @@ -501,6 +501,7 @@ unsigned int str2uint(const char *str); /* version.c */ bool jsonb_9_4_check_applicable(ClusterInfo *cluster); +bool protocol_negotiation_supported(const ClusterInfo *cluster); void old_9_6_invalidate_hash_indexes(ClusterInfo *cluster, bool check_mode); diff --git a/src/bin/pg_upgrade/dump.c b/src/bin/pg_upgrade/dump.c index e4c9349311a..f47c8d06211 100644 --- a/src/bin/pg_upgrade/dump.c +++ b/src/bin/pg_upgrade/dump.c @@ -21,9 +21,10 @@ generate_old_dump(void) /* run new pg_dumpall binary for globals */ exec_prog(UTILITY_LOG_FILE, NULL, true, true, - "\"%s/pg_dumpall\" %s --globals-only --quote-all-identifiers " + "\"%s/pg_dumpall\" %s%s --globals-only --quote-all-identifiers " "--binary-upgrade %s --no-sync -f \"%s/%s\"", new_cluster.bindir, cluster_conn_opts(&old_cluster), + protocol_negotiation_supported(&old_cluster) ? "" : " -d \"max_protocol_version=3.0\"", log_opts.verbose ? "--verbose" : "", log_opts.dumpdir, GLOBALS_DUMP_FILE); @@ -43,6 +44,9 @@ generate_old_dump(void) initPQExpBuffer(&connstr); appendPQExpBufferStr(&connstr, "dbname="); appendConnStrVal(&connstr, old_db->db_name); + if (!protocol_negotiation_supported(&old_cluster)) + appendPQExpBufferStr(&connstr, " max_protocol_version=3.0"); + initPQExpBuffer(&escaped_connstr); appendShellString(&escaped_connstr, connstr.data); termPQExpBuffer(&connstr); diff --git a/src/bin/pg_upgrade/server.c b/src/bin/pg_upgrade/server.c index eeeac3153f0..1eb8bc97c05 100644 --- a/src/bin/pg_upgrade/server.c +++ b/src/bin/pg_upgrade/server.c @@ -71,6 +71,8 @@ get_db_conn(ClusterInfo *cluster, const char *db_name) appendPQExpBufferStr(&conn_opts, " host="); appendConnStrVal(&conn_opts, cluster->sockdir); } + if (!protocol_negotiation_supported(cluster)) + appendPQExpBufferStr(&conn_opts, " max_protocol_version=3.0"); conn = PQconnectdb(conn_opts.data); termPQExpBuffer(&conn_opts); diff --git a/src/bin/pg_upgrade/task.c b/src/bin/pg_upgrade/task.c index d4cd487bad0..3d958527528 100644 --- a/src/bin/pg_upgrade/task.c +++ b/src/bin/pg_upgrade/task.c @@ -188,6 +188,8 @@ start_conn(const ClusterInfo *cluster, UpgradeTaskSlot *slot) appendPQExpBufferStr(&conn_opts, " host="); appendConnStrVal(&conn_opts, cluster->sockdir); } + if (!protocol_negotiation_supported(cluster)) + appendPQExpBufferStr(&conn_opts, " max_protocol_version=3.0"); slot->conn = PQconnectStart(conn_opts.data); diff --git a/src/bin/pg_upgrade/version.c b/src/bin/pg_upgrade/version.c index e709262837e..047670d4acb 100644 --- a/src/bin/pg_upgrade/version.c +++ b/src/bin/pg_upgrade/version.c @@ -28,6 +28,24 @@ jsonb_9_4_check_applicable(ClusterInfo *cluster) return false; } +/* + * Older servers can't support newer protocol versions, so their connection + * strings will need to lock max_protocol_version to 3.0. + */ +bool +protocol_negotiation_supported(const ClusterInfo *cluster) +{ + /* + * The February 2018 patch release (9.3.21, 9.4.16, 9.5.11, 9.6.7, and + * 10.2) added support for NegotiateProtocolVersion. But ClusterInfo only + * has information about the major version number. To ensure we can still + * upgrade older unpatched servers, just assume anything prior to PG11 + * can't negotiate. It's not possible for those servers to make use of + * newer protocols anyway, so nothing is lost. + */ + return (GET_MAJOR_VERSION(cluster->major_version) >= 1100); +} + /* * old_9_6_invalidate_hash_indexes() * 9.6 -> 10 -- 2.34.1