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Fix pg_basebackup with in-place tablespaces some more.

Browse Source 
Commit c6f2f01611 purported to make
this work, but problems remained. In a plain-format backup, the
files from an in-place tablespace got included in the tar file for
the main tablespace, which is wrong but it's not clear that it
has any user-visible consequences. In a tar-format backup, the
TABLESPACE_MAP option is used, and so we never iterated over
pg_tblspc and thus never backed up the in-place tablespaces
anywhere at all.

To fix this, reverse the changes in that commit, so that when we scan
pg_tblspc during a backup, we create tablespaceinfo objects even for
in-place tablespaces. We set the field that would normally contain the
absolute pathname to the relative path pg_tblspc/${TSOID}, and that's
good enough to make basebackup.c happy without any further changes.

However, pg_basebackup needs a couple of adjustments to make it work.
First, it needs to understand that a relative path for a tablespace
means it's an in-place tablespace.  Second, it needs to tolerate the
situation where restoring the main tablespace tries to create
pg_tblspc or a subdirectory and finds that it already exists, because
we restore user-defined tablespaces before the main tablespace.

Since in-place tablespaces are only intended for use in development
and testing, no back-patch.

Patch by me, reviewed by Thomas Munro and Michael Paquier.

Discussion: http://postgr.es/m/CA+TgmobwvbEp+fLq2PykMYzizcvuNv0a7gPMJtxOTMOuuRLMHg@mail.gmail.com
This commit is contained in:
Robert Haas
2023-04-18 11:23:34 -04:00
parent f180290847
commit 363e8f9115
4 changed files with 162 additions and 69 deletions
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116
src/backend/access/transam/xlog.c
View File

@@ -8454,9 +8454,8 @@ do_pg_backup_start(const char *backupidstr, bool fast, List **tablespaces,
char fullpath[MAXPGPATH + 10];
char linkpath[MAXPGPATH];
char *relpath = NULL;
int rllen;
StringInfoData escapedpath;
char *s;
PGFileType de_type;
/* Skip anything that doesn't look like a tablespace */
if (strspn(de->d_name, "0123456789") != strlen(de->d_name))
@@ -8464,66 +8463,83 @@ do_pg_backup_start(const char *backupidstr, bool fast, List **tablespaces,
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;
de_type = get_dirent_type(fullpath, de, false, ERROR);
rllen = readlink(fullpath, linkpath, sizeof(linkpath));
if (rllen < 0)
if (de_type == PGFILETYPE_LNK)
{
ereport(WARNING,
(errmsg("could not read symbolic link \"%s\": %m",
fullpath)));
StringInfoData escapedpath;
int rllen;
rllen = readlink(fullpath, linkpath, sizeof(linkpath));
if (rllen < 0)
{
ereport(WARNING,
(errmsg("could not read symbolic link \"%s\": %m",
fullpath)));
continue;
}
else if (rllen >= sizeof(linkpath))
{
ereport(WARNING,
(errmsg("symbolic link \"%s\" target is too long",
fullpath)));
continue;
}
linkpath[rllen] = '\0';
/*
* Relpath holds the relative path of the tablespace directory
* when it's located within PGDATA, or NULL if it's located
* elsewhere.
*/
if (rllen > datadirpathlen &&
strncmp(linkpath, DataDir, datadirpathlen) == 0 &&
IS_DIR_SEP(linkpath[datadirpathlen]))
relpath = pstrdup(linkpath + datadirpathlen + 1);
/*
* Add a backslash-escaped version of the link path to the
* tablespace map file.
*/
initStringInfo(&escapedpath);
for (s = linkpath; *s; s++)
{
if (*s == '\n' || *s == '\r' || *s == '\\')
appendStringInfoChar(&escapedpath, '\\');
appendStringInfoChar(&escapedpath, *s);
}
appendStringInfo(tblspcmapfile, "%s %s\n",
de->d_name, escapedpath.data);
pfree(escapedpath.data);
}
else if (de_type == PGFILETYPE_DIR)
{
/*
* It's possible to use allow_in_place_tablespaces to create
* directories directly under pg_tblspc, for testing purposes
* only.
*
* In this case, we store a relative path rather than an
* absolute path into the tablespaceinfo.
*/
snprintf(linkpath, sizeof(linkpath), "pg_tblspc/%s",
de->d_name);
relpath = pstrdup(linkpath);
}
else
{
/* Skip any other file type that appears here. */
continue;
}
else if (rllen >= sizeof(linkpath))
{
ereport(WARNING,
(errmsg("symbolic link \"%s\" target is too long",
fullpath)));
continue;
}
linkpath[rllen] = '\0';
/*
* Build a backslash-escaped version of the link path to include
* in the tablespace map file.
*/
initStringInfo(&escapedpath);
for (s = linkpath; *s; s++)
{
if (*s == '\n' || *s == '\r' || *s == '\\')
appendStringInfoChar(&escapedpath, '\\');
appendStringInfoChar(&escapedpath, *s);
}
/*
* Relpath holds the relative path of the tablespace directory
* when it's located within PGDATA, or NULL if it's located
* elsewhere.
*/
if (rllen > datadirpathlen &&
strncmp(linkpath, DataDir, datadirpathlen) == 0 &&
IS_DIR_SEP(linkpath[datadirpathlen]))
relpath = linkpath + datadirpathlen + 1;
ti = palloc(sizeof(tablespaceinfo));
ti->oid = pstrdup(de->d_name);
ti->path = pstrdup(linkpath);
ti->rpath = relpath ? pstrdup(relpath) : NULL;
ti->rpath = relpath;
ti->size = -1;
if (tablespaces)
*tablespaces = lappend(*tablespaces, ti);
appendStringInfo(tblspcmapfile, "%s %s\n",
ti->oid, escapedpath.data);
pfree(escapedpath.data);
}
FreeDir(tblspcdir);