Add some comments about the safety of accessing rolpassword without using

the normal heap_getattr() machinery.  Per Greg Stark.

diff --git a/src/backend/utils/init/flatfiles.c b/src/backend/utils/init/flatfiles.c
index e388d1edfdc0e6a532775a2a86c7f4a5f8b6f861..992fc70bb448ab4fb3c1bc55a901b3f93ffe999f 100644 (file)
--- a/src/backend/utils/init/flatfiles.c
+++ b/src/backend/utils/init/flatfiles.c
@@ -23,7 +23,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/utils/init/flatfiles.c,v 1.25 2007/04/06 04:21:43 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/init/flatfiles.c,v 1.26 2007/06/12 17:16:52 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -441,7 +441,10 @@ write_auth_file(Relation rel_authid, Relation rel_authmem)
         * We can't use heap_getattr() here because during startup we will not
         * have any tupdesc for pg_authid.  Fortunately it's not too hard to
         * work around this.  rolpassword is the first possibly-null field so
-        * we can compute its offset directly.
+        * we can compute its offset directly.  Note that this only works
+        * reliably because the preceding field (rolconnlimit) is int4, and
+        * therefore rolpassword is always 4-byte-aligned, and will be at
+        * the same offset no matter whether it uses 1-byte or 4-byte header.
         */
        tp = (char *) tup + tup->t_hoff;
        off = offsetof(FormData_pg_authid, rolpassword);
@@ -460,6 +463,10 @@ write_auth_file(Relation rel_authid, Relation rel_authmem)
            /*
             * The password probably shouldn't ever be out-of-line toasted; if
             * it is, ignore it, since we can't handle that in startup mode.
+            *
+            * It is entirely likely that it's 1-byte format not 4-byte, and
+            * theoretically possible that it's compressed inline, but textout
+            * should be able to handle those cases even in startup mode.
             */
            if (VARATT_IS_EXTERNAL(DatumGetPointer(datum)))
                auth_info[curr_role].rolpassword = pstrdup("");