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Don't choke on files that are removed while pg_rewind runs.

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If a file is removed from the source server, while pg_rewind is running, the
invocation of pg_read_binary_file() will fail. Use the just-added missing_ok
option to that function, to have it return NULL instead, and handle that
gracefully. And similarly for pg_ls_dir and pg_stat_file.

Reported by Fujii Masao, fix by Michael Paquier.
This commit is contained in:
Heikki Linnakangas 2015-06-28 21:35:51 +03:00
parent cb2acb1081
commit b36805f3c5
1 changed files with 30 additions and 7 deletions
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37
src/bin/pg_rewind/libpq_fetch.c
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@ -149,14 +149,14 @@ libpqProcessFileList(void)
sql =
"WITH RECURSIVE files (path, filename, size, isdir) AS (\n"
" SELECT '' AS path, filename, size, isdir FROM\n"
" (SELECT pg_ls_dir('.') AS filename) AS fn,\n"
" pg_stat_file(fn.filename) AS this\n"
" (SELECT pg_ls_dir('.', true, false) AS filename) AS fn,\n"
" pg_stat_file(fn.filename, true) AS this\n"
" UNION ALL\n"
" SELECT parent.path || parent.filename || '/' AS path,\n"
" fn, this.size, this.isdir\n"
" FROM files AS parent,\n"
" pg_ls_dir(parent.path || parent.filename) AS fn,\n"
" pg_stat_file(parent.path || parent.filename || '/' || fn) AS this\n"
" pg_ls_dir(parent.path || parent.filename, true, false) AS fn,\n"
" pg_stat_file(parent.path || parent.filename || '/' || fn, true) AS this\n"
" WHERE parent.isdir = 't'\n"
")\n"
"SELECT path || filename, size, isdir,\n"
@ -183,6 +183,15 @@ libpqProcessFileList(void)
char *link_target = PQgetvalue(res, i, 3);
file_type_t type;
if (PQgetisnull(res, 0, 1))
{
/*
* The file was removed from the server while the query was
* running. Ignore it.
*/
continue;
}
if (link_target[0])
type = FILE_TYPE_SYMLINK;
else if (isdir)
@ -259,8 +268,7 @@ receiveFileChunks(const char *sql)
}
if (PQgetisnull(res, 0, 0) ||
PQgetisnull(res, 0, 1) ||
PQgetisnull(res, 0, 2))
PQgetisnull(res, 0, 1))
{
pg_fatal("unexpected null values in result while fetching remote files\n");
}
@ -280,6 +288,21 @@ receiveFileChunks(const char *sql)
chunk = PQgetvalue(res, 0, 2);
/*
* It's possible that the file was deleted on remote side after we
* created the file map. In this case simply ignore it, as if it was
* not there in the first place, and move on.
*/
if (PQgetisnull(res, 0, 2))
{
pg_log(PG_DEBUG,
"received NULL chunk for file \"%s\", file has been deleted\n",
filename);
pg_free(filename);
PQclear(res);
continue;
}
pg_log(PG_DEBUG, "received chunk for file \"%s\", offset %d, size %d\n",
filename, chunkoff, chunksize);
@ -445,7 +468,7 @@ libpq_executeFileMap(filemap_t *map)
*/
sql =
"SELECT path, begin, \n"
" pg_read_binary_file(path, begin, len) AS chunk\n"
" pg_read_binary_file(path, begin, len, true) AS chunk\n"
"FROM fetchchunks\n";
receiveFileChunks(sql);