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 <[email protected]>
Author: Michaël Paquier <[email protected]>
Author: Álvaro Herrera <[email protected]>
Discussion: https://postgr.es/m/20220722081858[email protected]

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 657cc7ed1a58d23e2e1a56a19287372824a234c6..29d88e37f0fee4112e88cc58bfa5b6035b07f370 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -8319,6 +8319,25 @@ 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 ef5ce8c1caac28c4fd279ba87dca0e47b9a0d002..00fef8c1f424e7d3df2da9d66c68b65715b497f7 100644 (file)
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -10781,6 +10781,9 @@ do_pg_start_backup(const char *backupidstr, bool fast, TimeLineID *starttli_p,
            int         rllen;
            StringInfoData buflinkpath;
            char       *s = linkpath;
+#ifndef WIN32
+           struct stat st;
+#endif
 
            /* Skip special stuff */
            if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
@@ -10788,6 +10791,23 @@ 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.
+            */
+#ifndef WIN32
+           if (lstat(fullpath, &st) < 0)
+               ereport(LOG,
+                       (errcode_for_file_access(),
+                        errmsg("could not stat file \"%s\": %m",
+                               fullpath)));
+           else if (!S_ISLNK(st.st_mode))
+#else          /* WIN32 */
+           if (!pgwin32_is_junction(fullpath))
+#endif
+               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 350c21912a0d7dbe6e9e99d27b6b1aafdca50162..1e707988a0f2a7a257f80827415bc79693aa565c 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")));
@@ -565,16 +570,36 @@ 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 (mkdir(linkloc, S_IRWXU) < 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, S_IRWXU) != 0)
+   if (!in_place && chmod(location, S_IRWXU) != 0)
    {
        if (errno == ENOENT)
            ereport(ERROR,
@@ -623,13 +648,13 @@ 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 7ceb7d5cfc05dd9f625e9ed55a7be89e0ba63900..f886544f541f71523de2411174beb2c9ad004e7d 100644 (file)
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -16,6 +16,7 @@
 
 #include <sys/file.h>
 #include <signal.h>
+#include <sys/stat.h>
 #include <dirent.h>
 #include <fcntl.h>
 #include <math.h>
@@ -480,6 +481,9 @@ 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
@@ -504,6 +508,31 @@ 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 d4734cf133e349c5ebcd12c2717fc85d4195d003..5445a6ee5ead56e0c7d3ff6034424bfbb639dac8 100644 (file)
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -37,6 +37,7 @@
 #include "catalog/pg_authid.h"
 #include "commands/async.h"
 #include "commands/prepare.h"
+#include "commands/tablespace.h"
 #include "commands/user.h"
 #include "commands/vacuum.h"
 #include "commands/variable.h"
@@ -1605,6 +1606,17 @@ 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 ba8de32c7b050d2549eb37462c5f95e5d2acdc21..4c631798e36ce9b2d2aacaeb5729791088bdd041 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