In pg_upgrade, add C comment about why we don't try to do shared file

writes for logging.

diff --git a/contrib/pg_upgrade/pg_upgrade.h b/contrib/pg_upgrade/pg_upgrade.h
index df884bd684b6f4cbf0a2ab9cdecd6da28f738f60..6def748ae81f796e2053e520a5718d6dd7f3d7f3 100644 (file)
--- a/contrib/pg_upgrade/pg_upgrade.h
+++ b/contrib/pg_upgrade/pg_upgrade.h
@@ -207,6 +207,10 @@ typedef struct
         * because it is being used by another process." so we have to send all
         * other output to 'nul'.  Therefore, we set this to DEVNULL on Win32, and
         * it equals 'filename' on all other platforms.
+        *
+        * We could use the Windows pgwin32_open() flags to allow shared file
+        * writes but is unclear how all other tools would use those flags, so
+        * we just avoid it and log a little less on Windows.
         */
        char       *filename2;
        FILE       *fd;                         /* log FILE */