Allow "in place" tablespaces.

This is a backpatch to branches 10-14 of the following commits:

7170f2159fb2 Allow "in place" tablespaces.
c6f2f01611d4 Fix pg_basebackup with in-place tablespaces.
f6f0db4d6240 Fix pg_tablespace_location() with in-place tablespaces
7a7cd84893e0 doc: Remove mention to in-place tablespaces for pg_tablespace_location()
5344723755bd Remove unnecessary Windows-specific basebackup code.

In-place tablespaces were introduced as a testing helper mechanism, but
they are going to be used for a bugfix in WAL replay to be backpatched
to all stable branches.

I (Álvaro) had to adjust some code to account for lack of
get_dirent_type() in branches prior to 14.

Author: Thomas Munro <thomas.munro@gmail.com>
Author: Michaël Paquier <michael@paquier.xyz>
Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20220722081858.omhn2in5zt3g4nek@alvherre.pgsql

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e83361b23fd484048fa651b44c43f599411b2d08..8827685dd736f20e5e67dc5943badae9a149e12d 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -10369,6 +10369,25 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
     </para>
 
     <variablelist>
+     <varlistentry id="guc-allow-in-place-tablespaces" xreflabel="allow_in_place_tablespaces">
+      <term><varname>allow_in_place_tablespaces</varname> (<type>boolean</type>)
+      <indexterm>
+        <primary><varname>allow_in_place_tablespaces</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Allows tablespaces to be created as directories inside
+        <filename>pg_tblspc</filename>, when an empty location string
+        is provided to the <command>CREATE TABLESPACE</command> command.  This
+        is intended to allow testing replication scenarios where primary and
+        standby servers are running on the same machine.  Such directories
+        are likely to confuse backup tools that expect to find only symbolic
+        links in that location.  Only superusers can change this setting.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-allow-system-table-mods" xreflabel="allow_system_table_mods">
       <term><varname>allow_system_table_mods</varname> (<type>boolean</type>)
       <indexterm>

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index e1e5cc22c56136ace88cb5682f08a311e8b5afc7..be6234c38ed3da718d753e49e6bdd6af4c62b277 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -43,6 +43,7 @@
 #include "commands/progress.h"
 #include "commands/tablespace.h"
 #include "common/controldata_utils.h"
+#include "common/file_utils.h"
 #include "executor/instrument.h"
 #include "miscadmin.h"
 #include "pg_trace.h"
@@ -11168,6 +11169,14 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
 
                        snprintf(fullpath, sizeof(fullpath), "pg_tblspc/%s", de->d_name);
 
+                       /*
+                        * Skip anything that isn't a symlink/junction.  For testing only,
+                        * we sometimes use allow_in_place_tablespaces to create
+                        * directories directly under pg_tblspc, which would fail below.
+                        */
+                       if (get_dirent_type(fullpath, de, false, ERROR) != PGFILETYPE_LNK)
+                               continue;
+
 #if defined(HAVE_READLINK) || defined(WIN32)
                        rllen = readlink(fullpath, linkpath, sizeof(linkpath));
                        if (rllen < 0)

diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 5411638696b4d1436a56f62e9cde7ec61797377b..077dbd3a0020e2feb1ed402d382c1e4dc57f1f56 100644 (file)
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -87,6 +87,7 @@
 /* GUC variables */
 char      *default_tablespace = NULL;
 char      *temp_tablespaces = NULL;
+bool           allow_in_place_tablespaces = false;
 
 
 static void create_tablespace_directories(const char *location,
@@ -241,6 +242,7 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
        char       *location;
        Oid                     ownerId;
        Datum           newOptions;
+       bool            in_place;
 
        /* Must be super user */
        if (!superuser())
@@ -266,12 +268,15 @@ CreateTableSpace(CreateTableSpaceStmt *stmt)
                                (errcode(ERRCODE_INVALID_NAME),
                                 errmsg("tablespace location cannot contain single quotes")));
 
+       in_place = allow_in_place_tablespaces && strlen(location) == 0;
+
        /*
         * Allowing relative paths seems risky
         *
-        * this also helps us ensure that location is not empty or whitespace
+        * This also helps us ensure that location is not empty or whitespace,
+        * unless specifying a developer-only in-place tablespace.
         */
-       if (!is_absolute_path(location))
+       if (!in_place && !is_absolute_path(location))
                ereport(ERROR,
                                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                                 errmsg("tablespace location must be an absolute path")));
@@ -592,16 +597,36 @@ create_tablespace_directories(const char *location, const Oid tablespaceoid)
        char       *linkloc;
        char       *location_with_version_dir;
        struct stat st;
+       bool            in_place;
 
        linkloc = psprintf("pg_tblspc/%u", tablespaceoid);
-       location_with_version_dir = psprintf("%s/%s", location,
+
+       /*
+        * If we're asked to make an 'in place' tablespace, create the directory
+        * directly where the symlink would normally go.  This is a developer-only
+        * option for now, to facilitate regression testing.
+        */
+       in_place = strlen(location) == 0;
+
+       if (in_place)
+       {
+               if (MakePGDirectory(linkloc) < 0 && errno != EEXIST)
+                       ereport(ERROR,
+                                       (errcode_for_file_access(),
+                                        errmsg("could not create directory \"%s\": %m",
+                                                       linkloc)));
+       }
+
+       location_with_version_dir = psprintf("%s/%s", in_place ? linkloc : location,
                                                                                 TABLESPACE_VERSION_DIRECTORY);
 
        /*
         * Attempt to coerce target directory to safe permissions.  If this fails,
-        * it doesn't exist or has the wrong owner.
+        * it doesn't exist or has the wrong owner.  Not needed for in-place mode,
+        * because in that case we created the directory with the desired
+        * permissions.
         */
-       if (chmod(location, pg_dir_create_mode) != 0)
+       if (!in_place && chmod(location, pg_dir_create_mode) != 0)
        {
                if (errno == ENOENT)
                        ereport(ERROR,
@@ -650,13 +675,13 @@ create_tablespace_directories(const char *location, const Oid tablespaceoid)
        /*
         * In recovery, remove old symlink, in case it points to the wrong place.
         */
-       if (InRecovery)
+       if (!in_place && InRecovery)
                remove_tablespace_symlink(linkloc);
 
        /*
         * Create the symlink under PGDATA
         */
-       if (symlink(location, linkloc) < 0)
+       if (!in_place && symlink(location, linkloc) < 0)
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not create symbolic link \"%s\": %m",

diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index 88faf4dfd724a034f1e8f22657bef024cce91fc0..10b8384ef7082d3231992229fa104cfc867e42c7 100644 (file)
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -15,6 +15,7 @@
 #include "postgres.h"
 
 #include <sys/file.h>
+#include <sys/stat.h>
 #include <dirent.h>
 #include <fcntl.h>
 #include <math.h>
@@ -309,6 +310,9 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
        char            sourcepath[MAXPGPATH];
        char            targetpath[MAXPGPATH];
        int                     rllen;
+#ifndef WIN32
+       struct stat st;
+#endif
 
        /*
         * It's useful to apply this function to pg_class.reltablespace, wherein
@@ -333,6 +337,31 @@ pg_tablespace_location(PG_FUNCTION_ARGS)
         */
        snprintf(sourcepath, sizeof(sourcepath), "pg_tblspc/%u", tablespaceOid);
 
+       /*
+        * Before reading the link, check if the source path is a link or a
+        * junction point.  Note that a directory is possible for a tablespace
+        * created with allow_in_place_tablespaces enabled.  If a directory is
+        * found, a relative path to the data directory is returned.
+        */
+#ifdef WIN32
+       if (!pgwin32_is_junction(sourcepath))
+               PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
+#else
+       if (lstat(sourcepath, &st) < 0)
+       {
+               ereport(ERROR,
+                               (errcode_for_file_access(),
+                                errmsg("could not stat file \"%s\": %m",
+                                               sourcepath)));
+       }
+
+       if (!S_ISLNK(st.st_mode))
+               PG_RETURN_TEXT_P(cstring_to_text(sourcepath));
+#endif
+
+       /*
+        * In presence of a link or a junction point, return the path pointing to.
+        */
        rllen = readlink(sourcepath, targetpath, sizeof(targetpath));
        if (rllen < 0)
                ereport(ERROR,

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index d9346f711db5dfea91a374c11b2314141526e3c4..ef62bb81885494d783e82006335a6e0ad700c6a9 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -46,6 +46,7 @@
 #include "catalog/storage.h"
 #include "commands/async.h"
 #include "commands/prepare.h"
+#include "commands/tablespace.h"
 #include "commands/trigger.h"
 #include "commands/user.h"
 #include "commands/vacuum.h"
@@ -1952,6 +1953,17 @@ static struct config_bool ConfigureNamesBool[] =
                NULL, NULL, NULL
        },
 
+       {
+               {"allow_in_place_tablespaces", PGC_SUSET, DEVELOPER_OPTIONS,
+                       gettext_noop("Allows tablespaces directly inside pg_tblspc, for testing."),
+                       NULL,
+                       GUC_NOT_IN_SAMPLE
+               },
+               &allow_in_place_tablespaces,
+               false,
+               NULL, NULL, NULL
+       },
+
        {
                {"lo_compat_privileges", PGC_SUSET, COMPAT_OPTIONS_PREVIOUS,
                        gettext_noop("Enables backward compatibility mode for privilege checks on large objects."),

diff --git a/src/include/commands/tablespace.h b/src/include/commands/tablespace.h
index 49cfc8479a6117ad4440af5644036b50688772c9..f33ba51bd65006ad3b05bf71657f49aacd3daa0e 100644 (file)
--- a/src/include/commands/tablespace.h
+++ b/src/include/commands/tablespace.h
@@ -19,6 +19,8 @@
 #include "lib/stringinfo.h"
 #include "nodes/parsenodes.h"
 
+extern bool allow_in_place_tablespaces;
+
 /* XLOG stuff */
 #define XLOG_TBLSPC_CREATE             0x00
 #define XLOG_TBLSPC_DROP               0x10