Move TablespaceCreateDbspace() call into smgrcreate(), which is where it

probably should have been to begin with; this is to cover cases like
needing to recreate the per-db directory during WAL replay.
Also, fix heap_create to force pg_class.reltablespace to be zero instead
of the database's default tablespace; this makes the world safe for
CREATE DATABASE to handle all tables in the default tablespace alike,
as per previous discussion.  And force pg_class.reltablespace to zero
when creating a relation without physical storage (eg, a view); this
avoids possibly having dangling references in this column after a
subsequent DROP TABLESPACE.

src/backend/storage/smgr/smgr.c

@@ -11,12 +11,13 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/smgr/smgr.c,v 1.75 2004/07/01 00:51:07 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/smgr/smgr.c,v 1.76 2004/07/11 19:52:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
+#include "commands/tablespace.h"
 #include "storage/bufmgr.h"
 #include "storage/freespace.h"
 #include "storage/ipc.h"
@@ -309,6 +310,19 @@ smgrcreate(SMgrRelation reln, bool isTemp, bool isRedo)
 	PendingRelDelete *pending;
 	MemoryContext	old_cxt;
 
+	/*
+	 * We may be using the target table space for the first time in this
+	 * database, so create a per-database subdirectory if needed.
+	 *
+	 * XXX this is a fairly ugly violation of module layering, but this seems
+	 * to be the best place to put the check.  Maybe TablespaceCreateDbspace
+	 * should be here and not in commands/tablespace.c?  But that would imply
+	 * importing a lot of stuff that smgr.c oughtn't know, either.
+	 */
+	TablespaceCreateDbspace(reln->smgr_rnode.spcNode,
+							reln->smgr_rnode.dbNode,
+							isRedo);
+
 	if (! (*(smgrsw[reln->smgr_which].smgr_create)) (reln, isRedo))
 		ereport(ERROR,
 				(errcode_for_file_access(),