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 8723c7a9cfb1e836a972ac4cc0de6e6b350d87a5..f14c48da6cf057aed2c62773d64234ebda110135 100644 (file)
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -229,6 +229,9 @@ 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);
 }
 
 /*