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lmdb: ITS#8221 don't merge branch pages needlessly.

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Change-Id: I6b535f70392e081027d8803b6623b0c51f21ec8b
This commit is contained in:
Howard Chu 2015-09-26 16:50:28 +01:00 committed by Leo Yuriev
parent 8e7fbfa063
commit ef72fbaea6
1 changed files with 10 additions and 5 deletions
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15
mdb.c
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@ -7888,17 +7888,23 @@ mdb_rebalance(MDB_cursor *mc)
{ {
MDB_node *node; MDB_node *node;
int rc; int rc;
unsigned ptop, minkeys; unsigned ptop, minkeys, thresh;
MDB_cursor mn; MDB_cursor mn;
indx_t oldki; indx_t oldki;
minkeys = 1 + (IS_BRANCH(mc->mc_pg[mc->mc_top])); if (IS_BRANCH(mc->mc_pg[mc->mc_top])) {
minkeys = 2;
thresh = 1;
} else {
minkeys = 1;
thresh = FILL_THRESHOLD;
}
mdb_debug("rebalancing %s page %zu (has %u keys, %.1f%% full)", mdb_debug("rebalancing %s page %zu (has %u keys, %.1f%% full)",
IS_LEAF(mc->mc_pg[mc->mc_top]) ? "leaf" : "branch", IS_LEAF(mc->mc_pg[mc->mc_top]) ? "leaf" : "branch",
mdb_dbg_pgno(mc->mc_pg[mc->mc_top]), NUMKEYS(mc->mc_pg[mc->mc_top]), mdb_dbg_pgno(mc->mc_pg[mc->mc_top]), NUMKEYS(mc->mc_pg[mc->mc_top]),
(float)PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) / 10); (float)PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) / 10);
if (PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) >= FILL_THRESHOLD && if (PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) >= thresh &&
NUMKEYS(mc->mc_pg[mc->mc_top]) >= minkeys) { NUMKEYS(mc->mc_pg[mc->mc_top]) >= minkeys) {
mdb_debug("no need to rebalance page %zu, above fill threshold", mdb_debug("no need to rebalance page %zu, above fill threshold",
mdb_dbg_pgno(mc->mc_pg[mc->mc_top])); mdb_dbg_pgno(mc->mc_pg[mc->mc_top]));
@ -8032,8 +8038,7 @@ mdb_rebalance(MDB_cursor *mc)
* move one key from it. Otherwise we should try to merge them. * move one key from it. Otherwise we should try to merge them.
* (A branch page must never have less than 2 keys.) * (A branch page must never have less than 2 keys.)
*/ */
minkeys = 1 + (IS_BRANCH(mn.mc_pg[mn.mc_top])); if (PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) >= thresh && NUMKEYS(mn.mc_pg[mn.mc_top]) > minkeys) {
if (PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) >= FILL_THRESHOLD && NUMKEYS(mn.mc_pg[mn.mc_top]) > minkeys) {
rc = mdb_node_move(&mn, mc); rc = mdb_node_move(&mn, mc);
if (mc->mc_ki[ptop]) { if (mc->mc_ki[ptop]) {
oldki++; oldki++;