Tom Lane wrote:
"Heikki Linnakangas" <[EMAIL PROTECTED]> writes:
Attached is an updated version of my patch to refactor the
XLogOpenRelation/XLogReadBuffer interface, in preparation for the relation forks patch, and subsequently the FSM rewrite patch.


The code motion in md.c looks fairly bogus; was that a copy-and-paste
error?

This one?

*** a/src/backend/storage/smgr/md.c
--- b/src/backend/storage/smgr/md.c
***************
*** 208,216 **** mdcreate(SMgrRelation reln, bool isRedo)
        char       *path;
        File            fd;
- if (isRedo && reln->md_fd != NULL)
-               return;                                 /* created and opened 
already... */
- Assert(reln->md_fd == NULL); path = relpath(reln->smgr_rnode);
--- 208,213 ----

That's intentional. That check has been moved to smgrcreate(), so that it's done before calling TablespaceCreateDbSpace(). The reason for that is that smgrcreate() is now called for every XLogReadBuffer() invocation, so we want to make it exit quickly if there's nothing to do.

On second look though, I think we should actually leave that check in mdcreate(). Even though it'd be dead code since we do the same check in smgrcreate already, removing it changes the semantics of mdcreate(): it'd no longer be acceptable to call mdcreate() if the file is open already.

Otherwise it looks pretty sane, but I have one stylistic gripe:
I'm dubious about your willingness to assume that pfree() is enough for
getting rid of a fake relcache entry.  Relcache entries are complex
beasts and it may not continue to work to do that.  It's also possible
that we'd have additional resources attached to them someday.  So
I think it'd be worth having a FreeFakeRelcacheEntry() routine to
localize the knowledge of how to get rid of them.

Yeah, I guess you're right.

--
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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