ITS#8311 add comment

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 3f48891f257eace04d52f57cda92bf70ac1b341f..fc0340c51e2e33fe22eb62adc3b5b779e13e9588 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -8251,6 +8251,11 @@ mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno
        rp->mp_pad = mp->mp_pad;
        DPRINTF(("new right sibling: page %"Z"u", rp->mp_pgno));
 
+       /* Usually when splitting the root page, the cursor
+        * height is 1. But when called from mdb_update_key,
+        * the cursor height may be greater because it walks
+        * up the stack while finding the branch slot to update.
+        */
        if (mc->mc_top < 1) {
                if ((rc = mdb_page_new(mc, P_BRANCH, 1, &pp)))
                        goto done;