mdb_drop optimization

If we know there are no sub-DBs and no overflow pages, skip leaf scan.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 2e4a3d0011b0dfaebc0a2b09c9f259632cadd8ee..6c0ee3f0fc1d8a556d344c9090d8263956b1ab92 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -9660,8 +9660,11 @@ mdb_drop0(MDB_cursor *mc, int subs)
 
                /* DUPSORT sub-DBs have no ovpages/DBs. Omit scanning leaves.
                 * This also avoids any P_LEAF2 pages, which have no nodes.
+                * Also if the DB doesn't have sub-DBs and has no overflow
+                * pages, omit scanning leaves.
                 */
-               if (mc->mc_flags & C_SUB)
+               if ((mc->mc_flags & C_SUB) ||
+                       (!subs && !mc->mc_db->md_overflow_pages))
                        mdb_cursor_pop(mc);
 
                mdb_cursor_copy(mc, &mx);
@@ -9683,6 +9686,9 @@ mdb_drop0(MDB_cursor *mc, int subs)
                                                        pg, omp->mp_pages);
                                                if (rc)
                                                        goto done;
+                                               mc->mc_db->md_overflow_pages -= omp->mp_pages;
+                                               if (!mc->mc_db->md_overflow_pages && !subs)
+                                                       break;
                                        } else if (subs && (ni->mn_flags & F_SUBDATA)) {
                                                mdb_xcursor_init1(mc, ni);
                                                rc = mdb_drop0(&mc->mc_xcursor->mx_cursor, 0);
@@ -9690,6 +9696,8 @@ mdb_drop0(MDB_cursor *mc, int subs)
                                                        goto done;
                                        }
                                }
+                               if (!subs && !mc->mc_db->md_overflow_pages)
+                                       goto pop;
                        } else {
                                if ((rc = mdb_midl_need(&txn->mt_free_pgs, n)) != 0)
                                        goto done;
@@ -9711,6 +9719,7 @@ mdb_drop0(MDB_cursor *mc, int subs)
                                /* no more siblings, go back to beginning
                                 * of previous level.
                                 */
+pop:
                                mdb_cursor_pop(mc);
                                mc->mc_ki[0] = 0;
                                for (i=1; i<mc->mc_snum; i++) {