From 4b8dacfcef7ad16939ec8695019747fb45a80847 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Wed, 5 Sep 2012 18:10:15 -0700
Subject: [PATCH] Fix WAL file replacement during cascading replication on
Windows.
When the startup process restores a WAL file from the archive, it deletes
any old file with the same name and renames the new file in its place. On
Windows, however, when a file is deleted, it still lingers as long as a
process holds a file handle open on it. With cascading replication, a
walsender process can hold the old file open, so the rename() in the startup
process would fail. To fix that, rename the old file to a temporary name, to
make the original file name available for reuse, before deleting the old
file.
---
src/backend/access/transam/xlog.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 83d8f53a9a7..98d16f62bdf 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2844,7 +2844,33 @@ XLogFileRead(uint32 log, uint32 seg, int emode, TimeLineID tli,
XLogFilePath(xlogfpath, tli, log, seg);
if (stat(xlogfpath, &statbuf) == 0)
{
- if (unlink(xlogfpath) != 0)
+ char oldpath[MAXPGPATH];
+#ifdef WIN32
+ static unsigned int deletedcounter = 1;
+ /*
+ * On Windows, if another process (e.g a walsender process) holds
+ * the file open in FILE_SHARE_DELETE mode, unlink will succeed,
+ * but the file will still show up in directory listing until the
+ * last handle is closed, and we cannot rename the new file in its
+ * place until that. To avoid that problem, rename the old file to
+ * a temporary name first. Use a counter to create a unique
+ * filename, because the same file might be restored from the
+ * archive multiple times, and a walsender could still be holding
+ * onto an old deleted version of it.
+ */
+ snprintf(oldpath, MAXPGPATH, "%s.deleted%u",
+ xlogfpath, deletedcounter++);
+ if (rename(xlogfpath, oldpath) != 0)
+ {
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not rename file \"%s\" to \"%s\": %m",
+ xlogfpath, oldpath)));
+ }
+#else
+ strncpy(oldpath, xlogfpath, MAXPGPATH);
+#endif
+ if (unlink(oldpath) != 0)
ereport(FATAL,
(errcode_for_file_access(),
errmsg("could not remove file \"%s\": %m",
--
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