WT-2287: Add support for a WT_SESSION.rebalance method that rebuilds the

underlying btree, correcting any imbalance.

SConstruct

@@ -290,6 +290,7 @@ wtbin = env.Program("wt", [
     "src/utilities/util_misc.c",
     "src/utilities/util_printlog.c",
     "src/utilities/util_read.c",
+    "src/utilities/util_rebalance.c",
     "src/utilities/util_rename.c",
     "src/utilities/util_salvage.c",
     "src/utilities/util_stat.c",

build_posix/Make.base

@@ -31,6 +31,7 @@ wt_SOURCES =\
 	src/utilities/util_misc.c \
 	src/utilities/util_printlog.c \
 	src/utilities/util_read.c \
+	src/utilities/util_rebalance.c \
 	src/utilities/util_rename.c \
 	src/utilities/util_salvage.c \
 	src/utilities/util_stat.c \

build_win/filelist.win

@@ -31,6 +31,7 @@ src/btree/bt_misc.c
 src/btree/bt_ovfl.c
 src/btree/bt_page.c
 src/btree/bt_read.c
+src/btree/bt_rebalance.c
 src/btree/bt_ret.c
 src/btree/bt_slvg.c
 src/btree/bt_split.c

dist/api_data.py

@@ -564,6 +564,7 @@ def __cmp__(self, other):
             'mutex',
             'overflow',
             'read',
+            'rebalance',
             'reconcile',
             'recovery',
             'salvage',
@@ -892,6 +893,7 @@ def __cmp__(self, other):
         type='list'),
 ]),
 
+'WT_SESSION.rebalance' : Method([]),
 'WT_SESSION.rename' : Method([]),
 'WT_SESSION.reset' : Method([]),
 'WT_SESSION.salvage' : Method([

dist/filelist

@@ -31,6 +31,7 @@ src/btree/bt_misc.c
 src/btree/bt_ovfl.c
 src/btree/bt_page.c
 src/btree/bt_read.c
+src/btree/bt_rebalance.c
 src/btree/bt_ret.c
 src/btree/bt_slvg.c
 src/btree/bt_split.c

dist/flags.py

@@ -70,6 +70,7 @@
         'VERB_MUTEX',
         'VERB_OVERFLOW',
         'VERB_READ',
+        'VERB_REBALANCE',
         'VERB_RECONCILE',
         'VERB_RECOVERY',
         'VERB_SALVAGE',

dist/s_string.ok

@@ -254,6 +254,7 @@ RNG
 RPC
 RUNDIR
 Radu
+Rebalance
 RedHat
 Redistributions
 Resize
@@ -857,6 +858,7 @@ readlock
 readonly
 readunlock
 realloc
+rebalance
 rebalancing
 recno
 recnos

examples/c/ex_all.c

@@ -673,6 +673,10 @@ session_ops(WT_SESSION *session)
 	ret = session->compact(session, "table:mytable", NULL);
 	/*! [Compact a table] */
 
+	/*! [Rebalance a table] */
+	ret = session->rebalance(session, "table:old", NULL);
+	/*! [Rebalance a table] */
+
 	/*! [Rename a table] */
 	ret = session->rename(session, "table:old", "table:new", NULL);
 	/*! [Rename a table] */

lang/java/java_doc.i

@@ -36,6 +36,7 @@ COPYDOC(__wt_session, WT_SESSION, drop)
 COPYDOC(__wt_session, WT_SESSION, join)
 COPYDOC(__wt_session, WT_SESSION, log_flush)
 COPYDOC(__wt_session, WT_SESSION, log_printf)
+COPYDOC(__wt_session, WT_SESSION, rebalance)
 COPYDOC(__wt_session, WT_SESSION, rename)
 COPYDOC(__wt_session, WT_SESSION, reset)
 COPYDOC(__wt_session, WT_SESSION, salvage)

src/btree/bt_handle.c

@@ -105,14 +105,23 @@ __wt_btree_open(WT_SESSION_IMPL *session, const char *op_cfg[])
 			WT_ERR(__wt_btree_tree_open(
 			    session, root_addr, root_addr_size));
 
-			/* Warm the cache, if possible. */
-			WT_WITH_PAGE_INDEX(session,
-			    ret = __btree_preload(session));
-			WT_ERR(ret);
-
-			/* Get the last record number in a column-store file. */
-			if (btree->type != BTREE_ROW)
-				WT_ERR(__btree_get_last_recno(session));
+			/*
+			 * Rebalance uses the cache, but only wants the root
+			 * page, nothing else.
+			 */
+			if (!F_ISSET(btree, WT_BTREE_REBALANCE)) {
+				/* Warm the cache, if possible. */
+				WT_WITH_PAGE_INDEX(session,
+				    ret = __btree_preload(session));
+				WT_ERR(ret);
+
+				/*
+				 * Get the last record number in a column-store
+				 * file.
+				 */
+				if (btree->type != BTREE_ROW)
+					WT_ERR(__btree_get_last_recno(session));
+			}
 		}
 	}