Ensure that creation of an empty relfile is fsync'd at checkpoint.

If you create a table and don't insert any data into it, the relation file
is never fsync'd. You don't lose data, because an empty table doesn't have
any data to begin with, but if you crash and lose the file, subsequent
operations on the table will fail with "could not open file" error.

To fix, register an fsync request in mdcreate(), like we do for mdwrite().

Per discussion, we probably should also fsync the containing directory
after creating a new file. But that's a separate and much wider issue.

Backpatch to all supported versions.

Reviewed-by: Andres Freund, Thomas Munro
Discussion: https://www.postgresql.org/message-id/d47d8122-415e-425c-d0a2-e0160829702d%40iki.fi

diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 51617e17c189889ef5c9dacf8be147a1a62f9433..825b58dc416f20d1467c8a6eb958af878161b4a6 100644 (file)
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -225,6 +225,9 @@ mdcreate(SMgrRelation reln, ForkNumber forkNum, bool isRedo)
    mdfd = &reln->md_seg_fds[forkNum][0];
    mdfd->mdfd_vfd = fd;
    mdfd->mdfd_segno = 0;
+
+   if (!SmgrIsTemp(reln))
+       register_dirty_segment(reln, forkNum, mdfd);
 }
 
 /*