From ee26517b5d909ab37bfddc5b91f59585e2512726 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Wed, 4 Nov 2015 20:38:30 +0000
Subject: [PATCH] mdbx: backpost - ITS#8300 fix rebalance after node_move.

ITS#8258, ITS#7829 fixes checked parent index to see if we were moving
from a left neighbor. Should have just checked to see if current index
was 0, meaning we added on the left. (Parent index may not tell us
anything meaningful after a nested rebalance.)

Includes:

 - ITS#8300 fix node_move
   Don't adjust other cursors when we added a node on the right.

 - ITS#8300 more for node_move fixups
   When moving a node from the right neighbor, a different
   adjustment is needed.

 - ITS#8300 simplify

 - ITS#8300 more for node_move
   When moving a node from one page to another, make sure other cursors'
   parent index gets adjusted too.
---
 CHANGES |  1 +
 mdb.c   | 67 ++++++++++++++++++++++++++++++++++++---------------------
 2 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/CHANGES b/CHANGES
index 05976ffa..0b63a13d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -9,6 +9,7 @@ LMDB 0.9.17 Release Engineering
 	Fix ITS#8263 cursor_put cursor tracking
 	Fix ITS#8264 cursor_del cursor tracking
 	Fix ITS#8299 mdb_del cursor tracking
+	Fix ITS#8300 mdb_del cursor tracking
 	Fix ITS#7771 fakepage cursor tracking
 	Fix ITS#7789 ensure mapsize >= pages in use
 	Fix ITS#7971 mdb_txn_renew0() new reader slots
diff --git a/mdb.c b/mdb.c
index 671e5312..7840d16e 100644
--- a/mdb.c
+++ b/mdb.c
@@ -7738,32 +7738,48 @@ mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst)
 		/* Adjust other cursors pointing to mp */
 		MDB_cursor *m2, *m3;
 		MDB_dbi dbi = csrc->mc_dbi;
-		MDB_page *mp;
+		MDB_page *mpd, *mps;
 
-		mp = cdst->mc_pg[csrc->mc_top];
-		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
-			if (csrc->mc_flags & C_SUB)
-				m3 = &m2->mc_xcursor->mx_cursor;
-			else
-				m3 = m2;
-			if (m3 == cdst) continue;
-			if (m3->mc_pg[csrc->mc_top] == mp && m3->mc_ki[csrc->mc_top] >=
-				cdst->mc_ki[csrc->mc_top]) {
-				m3->mc_ki[csrc->mc_top]++;
+		mps = csrc->mc_pg[csrc->mc_top];
+		/* If we're adding on the left, bump others up */
+		if (!cdst->mc_ki[csrc->mc_top]) {
+			mpd = cdst->mc_pg[csrc->mc_top];
+			for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				if (csrc->mc_flags & C_SUB)
+					m3 = &m2->mc_xcursor->mx_cursor;
+				else
+					m3 = m2;
+				if (m3 != cdst &&
+					m3->mc_pg[csrc->mc_top] == mpd &&
+					m3->mc_ki[csrc->mc_top] >= cdst->mc_ki[csrc->mc_top]) {
+					m3->mc_ki[csrc->mc_top]++;
+				}
+				if (m3 !=csrc &&
+					m3->mc_pg[csrc->mc_top] == mps &&
+					m3->mc_ki[csrc->mc_top] == csrc->mc_ki[csrc->mc_top]) {
+					m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
+					m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+					m3->mc_ki[csrc->mc_top-1]++;
+				}
 			}
-		}
-
-		mp = csrc->mc_pg[csrc->mc_top];
-		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
-			if (csrc->mc_flags & C_SUB)
-				m3 = &m2->mc_xcursor->mx_cursor;
-			else
-				m3 = m2;
-			if (m3 == csrc) continue;
-			if (m3->mc_pg[csrc->mc_top] == mp && m3->mc_ki[csrc->mc_top] ==
-				csrc->mc_ki[csrc->mc_top]) {
-				m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
-				m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+		} else
+		/* Adding on the right, bump others down */
+		{
+			for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
+				if (csrc->mc_flags & C_SUB)
+					m3 = &m2->mc_xcursor->mx_cursor;
+				else
+					m3 = m2;
+				if (m3 == csrc) continue;
+				if (m3->mc_pg[csrc->mc_top] == mps) {
+					if (!m3->mc_ki[csrc->mc_top]) {
+						m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
+						m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
+						m3->mc_ki[csrc->mc_top-1]--;
+					} else {
+						m3->mc_ki[csrc->mc_top]--;
+					}
+				}
 			}
 		}
 	}
@@ -8151,7 +8167,8 @@ mdb_rebalance(MDB_cursor *mc)
 	 */
 	if (PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) >= thresh && NUMKEYS(mn.mc_pg[mn.mc_top]) > minkeys) {
 		rc = mdb_node_move(&mn, mc);
-		if (mc->mc_ki[mc->mc_top-1]) {
+		if (!mc->mc_ki[mc->mc_top]) {
+			/* if we inserted on left, bump position up */
 			oldki++;
 		}
 	} else {