First step in attempt to fix tree at runtime: create upper levels

and new root page if old root one was splitted but new root page
wasn't created.
New code is protected by FixBTree bool flag setted to FALSE, so
nothing should be affected by this untested approach.

src/backend/access/nbtree/nbtpage.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.47 2001/01/24 19:42:48 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtpage.c,v 1.48 2001/01/26 01:24:31 vadim Exp $
  *
  *	NOTES
  *	   Postgres btree pages look like ordinary relation pages.	The opaque
@@ -28,6 +28,8 @@
 #include "miscadmin.h"
 #include "storage/lmgr.h"
 
+extern bool FixBTree;	/* comments in nbtree.c */
+extern Buffer _bt_fixroot(Relation rel, Buffer oldrootbuf, bool release);
 
 /*
  *	We use high-concurrency locking on btrees.	There are two cases in
@@ -237,7 +239,58 @@ _bt_getroot(Relation rel, int access)
 
 	if (! P_ISROOT(rootopaque))
 	{
-		/* it happened, try again */
+		/*
+		 * It happened, but if root page splitter failed to create
+		 * new root page then we'll go in loop trying to call
+		 * _bt_getroot again and again.
+		 */
+		if (FixBTree)
+		{
+			Buffer	newrootbuf;
+
+check_parent:;
+			if (rootopaque->btpo_parent == BTREE_METAPAGE)	/* unupdated! */
+			{
+				LockBuffer(rootbuf, BUFFER_LOCK_UNLOCK);
+				LockBuffer(rootbuf, BT_WRITE);
+
+				/* handle concurrent fix of root page */
+				if (rootopaque->btpo_parent == BTREE_METAPAGE)	/* unupdated! */
+				{
+					newrootbuf = _bt_fixroot(rel, rootbuf, true);
+					LockBuffer(newrootbuf, BUFFER_LOCK_UNLOCK);
+					LockBuffer(newrootbuf, BT_READ);
+					rootbuf = newrootbuf;
+					rootpage = BufferGetPage(rootbuf);
+					rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
+					/* New root might be splitted while changing lock */
+					if (P_ISROOT(rootopaque))
+						return(rootbuf);
+					/* rootbuf is read locked */
+					goto check_parent;
+				}
+				else	/* someone else already fixed root */
+				{
+					LockBuffer(rootbuf, BUFFER_LOCK_UNLOCK);
+					LockBuffer(rootbuf, BT_READ);
+				}
+			}
+			/*
+			 * Ok, here we have old root page with btpo_parent pointing
+			 * to upper level - check parent page because of there is
+			 * good chance that parent is root page.
+			 */
+			newrootbuf = _bt_getbuf(rel, rootopaque->btpo_parent, BT_READ);
+			_bt_relbuf(rel, rootbuf, BT_READ);
+			rootbuf = newrootbuf;
+			rootpage = BufferGetPage(rootbuf);
+			rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
+			if (P_ISROOT(rootopaque))
+				return(rootbuf);
+			/* no luck -:( */
+		}
+
+		/* try again */
 		_bt_relbuf(rel, rootbuf, BT_READ);
 		return _bt_getroot(rel, access);
 	}

src/backend/access/nbtree/nbtree.c

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtree.c,v 1.75 2001/01/24 19:42:48 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtree.c,v 1.76 2001/01/26 01:24:31 vadim Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,13 +26,18 @@
 #include "executor/executor.h"
 #include "miscadmin.h"
 #include "storage/sinval.h"
-
+#include "access/xlogutils.h"
 
 bool		BuildingBtree = false;		/* see comment in btbuild() */
-bool		FastBuild = true;	/* use sort/build instead of insertion
-								 * build */
+bool		FastBuild = true;	/* use sort/build instead */
+								/* of insertion build */
 
-#include "access/xlogutils.h"
+
+/*
+ * TEMPORARY FLAG FOR TESTING NEW FIX TREE
+ * CODE WITHOUT AFFECTING ANYONE ELSE
+ */
+bool		FixBTree = false;
 
 static void _bt_restscan(IndexScanDesc scan);