Date: Fri, 25 Sep 2020 15:47:49 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: pgsql-hackers@postgresql.org
Subject: Re: pg_upgrade: fail early if a tablespace dir already exists for
 new cluster version
Message-ID: <20200925204749.GW23631@telsasoft.com>
References: <20200925005531.GJ23631@telsasoft.com>
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Added at
https://commitfest.postgresql.org/30/2739/

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 filename="v2-0001-pg_upgrade-check-to-avoid-tablespace-failure-mode.patch"

From 831246aa6d6837b2b0da7c96ad2f44ffd6cd3951 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryzbyj@telsasoft.com>
Date: Thu, 24 Sep 2020 19:49:40 -0500
Subject: [PATCH v2] pg_upgrade --check to avoid tablespace failure mode

---
 src/bin/pg_upgrade/check.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/src/bin/pg_upgrade/check.c b/src/bin/pg_upgrade/check.c
index 2f7aa632c5..154e3d249e 100644
--- a/src/bin/pg_upgrade/check.c
+++ b/src/bin/pg_upgrade/check.c
@@ -13,6 +13,7 @@
 #include "fe_utils/string_utils.h"
 #include "mb/pg_wchar.h"
 #include "pg_upgrade.h"
+#include "common/relpath.h"
 
 static void check_new_cluster_is_empty(void);
 static void check_databases_are_compatible(void);
@@ -27,6 +28,7 @@ static void check_for_tables_with_oids(ClusterInfo *cluster);
 static void check_for_reg_data_type_usage(ClusterInfo *cluster);
 static void check_for_jsonb_9_4_usage(ClusterInfo *cluster);
 static void check_for_pg_role_prefix(ClusterInfo *cluster);
+static void check_for_existing_tablespace_dirs(ClusterInfo *new_cluster);
 static char *get_canonical_locale_name(int category, const char *locale);
 
 
@@ -187,6 +189,8 @@ check_new_cluster(void)
 	check_is_install_user(&new_cluster);
 
 	check_for_prepared_transactions(&new_cluster);
+
+	check_for_existing_tablespace_dirs(&new_cluster);
 }
 
 
@@ -542,6 +546,39 @@ create_script_for_cluster_analyze(char **analyze_script_file_name)
 }
 
 
+/*
+ * Check that tablespace dirs do not already exist for new cluster version.
+ * If they did, it'd cause an error while restoring global objects.
+ * This allows failing earlier rather than only after dumping schema.
+ *
+ * Note, v8.4 has no tablespace_suffix, which is fine so long as the version we
+ * being upgraded *to* has a suffix.
+ */
+static void
+check_for_existing_tablespace_dirs(ClusterInfo *new_cluster)
+{
+	char	old_tablespace_dir[MAXPGPATH];
+
+	prep_status("Checking for pre-existing tablespace directories");
+
+	for (int tblnum = 0; tblnum < os_info.num_old_tablespaces; tblnum++)
+	{
+		struct stat statbuf;
+		snprintf(old_tablespace_dir, MAXPGPATH, "%s%s",
+				os_info.old_tablespaces[tblnum],
+				new_cluster->tablespace_suffix);
+
+		canonicalize_path(old_tablespace_dir);
+
+		// XXX: lstat ?
+		if (stat(old_tablespace_dir, &statbuf) == 0 || errno != ENOENT)
+			pg_fatal("tablespace directory already exists for new cluster version: \"%s\"\n",
+					 old_tablespace_dir);
+	}
+
+	check_ok();
+}
+
 /*
  * create_script_for_old_cluster_deletion()
  *
-- 
2.17.0


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