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 62d56ec52dddcfc6fd291f898836bae687baba3f..5418452261d5df81bba3bc9bfff64d0bbe3638e0 100644 (file)
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -334,6 +334,9 @@ 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);
 }
 
 /*