Further fixes for per-tablespace options patch.

Add missing varlena header to TableSpaceOpts structure.  And, per
Tom Lane, instead of calling tablespace_reloptions in CacheMemoryContext,
call it in the caller's memory context and copy the value over
afterwards, to reduce the chances of a session-lifetime memory leak.

src/backend/utils/cache/spccache.c

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/spccache.c,v 1.3 2010/01/06 23:00:02 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/spccache.c,v 1.4 2010/01/07 03:53:08 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -142,7 +142,6 @@ get_tablespace(Oid spcid)
 	{
 		Datum	datum;
 		bool	isNull;
-		MemoryContext octx;
 
 		datum = SysCacheGetAttr(TABLESPACEOID,
 								tp,
@@ -152,10 +151,9 @@ get_tablespace(Oid spcid)
 			opts = NULL;
 		else
 		{
-			/* XXX should NOT do the parsing work in CacheMemoryContext */
-			octx = MemoryContextSwitchTo(CacheMemoryContext);
-			opts = (TableSpaceOpts *) tablespace_reloptions(datum, false);
-			MemoryContextSwitchTo(octx);
+			bytea *bytea_opts = tablespace_reloptions(datum, false);
+			opts = MemoryContextAlloc(CacheMemoryContext, VARSIZE(bytea_opts));
+			memcpy(opts, bytea_opts, VARSIZE(bytea_opts));
 		}
 		ReleaseSysCache(tp);
 	}

src/include/commands/tablespace.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/tablespace.h,v 1.22 2010/01/05 21:53:59 rhaas Exp $
+ * $PostgreSQL: pgsql/src/include/commands/tablespace.h,v 1.23 2010/01/07 03:53:08 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -34,6 +34,7 @@ typedef struct xl_tblspc_drop_rec
 
 typedef struct TableSpaceOpts
 {
+	int32		vl_len_;		/* varlena header (do not touch directly!) */
 	float8		random_page_cost;
 	float8		seq_page_cost;
 } TableSpaceOpts;