Fix issue with file handle retention during CREATE DATABASE in pg_restore

During upgrades, when pg_restore performs CREATE DATABASE, the
bgwriter or checkpointer may flush buffers and hold a file handle
for the table. This causes issues if the table needs to be re-created
later (e.g., after a TRUNCATE command), especially on OSes like older
versions of Windows, where unlinked files aren't fully removed until
they are no longer open.

This commit fixes the issue by checking for STATUS_DELETE_PENDING and
calling WaitForProcSignalBarrier, ensuring that all smgr file descriptors
are closed across all backends before retrying the file operation.

Author: vigneshwaran-c

src/backend/storage/smgr/md.c

@@ -35,6 +35,7 @@
 #include "storage/bufmgr.h"
 #include "storage/fd.h"
 #include "storage/md.h"
+#include "storage/procsignal.h"
 #include "storage/relfilelocator.h"
 #include "storage/smgr.h"
 #include "storage/sync.h"
@@ -214,6 +215,9 @@ mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo)
 	MdfdVec    *mdfd;
 	RelPathStr	path;
 	File		fd;
+#if defined(WIN32) && !defined(__CYGWIN__)
+	bool		retryattempted = false;
+#endif
 
 	if (isRedo && reln->md_num_open_segs[forknum] > 0)
 		return;					/* created and opened already... */
@@ -235,6 +239,9 @@ mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo)
 
 	path = relpath(reln->smgr_rlocator, forknum);
 
+#if defined(WIN32) && !defined(__CYGWIN__)
+retry:
+#endif
 	fd = PathNameOpenFile(path.str, _mdfd_open_flags() | O_CREAT | O_EXCL);
 
 	if (fd < 0)
@@ -245,6 +252,15 @@ mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo)
 			fd = PathNameOpenFile(path.str, _mdfd_open_flags());
 		if (fd < 0)
 		{
+#if defined(WIN32) && !defined(__CYGWIN__)
+			if (!retryattempted && pg_RtlGetLastNtStatus() == STATUS_DELETE_PENDING)
+			{
+				retryattempted = true;
+				WaitForProcSignalBarrier(EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SMGRRELEASE));
+				goto retry;
+			}
+#endif
+
 			/* be sure to report the error reported by create, not open */
 			errno = save_errno;
 			ereport(ERROR,