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pg_upgrade: Use max_protocol_version=3.0 for older servers

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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.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAOYmi%2B%3D4QhCjssfNEoZVK8LPtWxnfkwT5p-PAeoxtG9gpNjqOQ%40mail.gmail.com
Backpatch-through: 14
This commit is contained in:
Jacob Champion 2026-02-24 14:01:54 -08:00
parent 3eb6f61958
commit e726620d20
4 changed files with 39 additions and 1 deletions
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6
src/bin/pg_upgrade/dump.c
View file

@ -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 -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);

1
src/bin/pg_upgrade/pg_upgrade.h
View file

@ -449,6 +449,7 @@ bool check_for_data_types_usage(ClusterInfo *cluster,
bool check_for_data_type_usage(ClusterInfo *cluster,
const char *type_name,
const char *output_path);
bool protocol_negotiation_supported(const ClusterInfo *cluster);
void old_9_3_check_for_line_data_type_usage(ClusterInfo *cluster);
void old_9_6_check_for_unknown_data_type_usage(ClusterInfo *cluster);
void old_9_6_invalidate_hash_indexes(ClusterInfo *cluster,

2
src/bin/pg_upgrade/server.c
View file

@ -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);

31
src/bin/pg_upgrade/version.c
View file

@ -241,6 +241,37 @@ old_9_6_check_for_unknown_data_type_usage(ClusterInfo *cluster)
check_ok();
}
/*
* 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)
{
/*
* Back-branch-specific complication: in libpq versions prior to PG18,
* max_protocol_version isn't supported. But we also don't need to worry
* about newer protocol versions being used in that case, so just lie and
* return true.
*
* (Checking for a libpq version that's newer than this branch looks very
* strange, but distributions are allowed to link older pg_upgrade
* binaries against the newest release of libpq.)
*/
if (PQlibVersion() < 180000)
return true;
/*
* 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