From 310b656a2e1b81c039baf8ee4eeece7468c2b41e Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@symas.com>
Date: Sat, 12 Oct 2013 09:34:40 -0700
Subject: [PATCH] ITS#7589 avoid wasting space in mdb_page_split
Also, check the split point on branch pages as well as leaf pages.
---
libraries/liblmdb/mdb.c | 425 ++++++++++++++++++++--------------------
1 file changed, 209 insertions(+), 216 deletions(-)
diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 91a84f091f..39635117cf 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -7376,10 +7376,11 @@ mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno
unsigned int nflags)
{
unsigned int flags;
- int rc = MDB_SUCCESS, ins_new = 0, new_root = 0, newpos = 1, did_split = 0;
+ int rc = MDB_SUCCESS, new_root = 0, did_split = 0;
indx_t newindx;
pgno_t pgno = 0;
unsigned int i, j, split_indx, nkeys, pmax;
+ MDB_env *env = mc->mc_txn->mt_env;
MDB_node *node;
MDB_val sepkey, rkey, xdata, *rdata = &xdata;
MDB_page *copy;
@@ -7390,10 +7391,11 @@ mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno
mp = mc->mc_pg[mc->mc_top];
newindx = mc->mc_ki[mc->mc_top];
+ nkeys = NUMKEYS(mp);
- DPRINTF(("-----> splitting %s page %"Z"u and adding [%s] at index %i",
+ DPRINTF(("-----> splitting %s page %"Z"u and adding [%s] at index %i/%i",
IS_LEAF(mp) ? "leaf" : "branch", mp->mp_pgno,
- DKEY(newkey), mc->mc_ki[mc->mc_top]));
+ DKEY(newkey), mc->mc_ki[mc->mc_top], nkeys));
/* Create a right sibling. */
if ((rc = mdb_page_new(mc, mp->mp_flags, 1, &rp)))
@@ -7440,141 +7442,148 @@ mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno
sepkey = *newkey;
split_indx = newindx;
nkeys = 0;
- goto newsep;
- }
+ } else {
- nkeys = NUMKEYS(mp);
- split_indx = nkeys / 2;
- if (newindx < split_indx)
- newpos = 0;
-
- if (IS_LEAF2(rp)) {
- char *split, *ins;
- int x;
- unsigned int lsize, rsize, ksize;
- /* Move half of the keys to the right sibling */
- copy = NULL;
- x = mc->mc_ki[mc->mc_top] - split_indx;
- ksize = mc->mc_db->md_pad;
- split = LEAF2KEY(mp, split_indx, ksize);
- rsize = (nkeys - split_indx) * ksize;
- lsize = (nkeys - split_indx) * sizeof(indx_t);
- mp->mp_lower -= lsize;
- rp->mp_lower += lsize;
- mp->mp_upper += rsize - lsize;
- rp->mp_upper -= rsize - lsize;
- sepkey.mv_size = ksize;
- if (newindx == split_indx) {
- sepkey.mv_data = newkey->mv_data;
- } else {
- sepkey.mv_data = split;
- }
- if (x<0) {
- ins = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], ksize);
- memcpy(rp->mp_ptrs, split, rsize);
- sepkey.mv_data = rp->mp_ptrs;
- memmove(ins+ksize, ins, (split_indx - mc->mc_ki[mc->mc_top]) * ksize);
- memcpy(ins, newkey->mv_data, ksize);
- mp->mp_lower += sizeof(indx_t);
- mp->mp_upper -= ksize - sizeof(indx_t);
+ split_indx = (nkeys+1) / 2;
+
+ if (IS_LEAF2(rp)) {
+ char *split, *ins;
+ int x;
+ unsigned int lsize, rsize, ksize;
+ /* Move half of the keys to the right sibling */
+ copy = NULL;
+ x = mc->mc_ki[mc->mc_top] - split_indx;
+ ksize = mc->mc_db->md_pad;
+ split = LEAF2KEY(mp, split_indx, ksize);
+ rsize = (nkeys - split_indx) * ksize;
+ lsize = (nkeys - split_indx) * sizeof(indx_t);
+ mp->mp_lower -= lsize;
+ rp->mp_lower += lsize;
+ mp->mp_upper += rsize - lsize;
+ rp->mp_upper -= rsize - lsize;
+ sepkey.mv_size = ksize;
+ if (newindx == split_indx) {
+ sepkey.mv_data = newkey->mv_data;
+ } else {
+ sepkey.mv_data = split;
+ }
+ if (x<0) {
+ ins = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], ksize);
+ memcpy(rp->mp_ptrs, split, rsize);
+ sepkey.mv_data = rp->mp_ptrs;
+ memmove(ins+ksize, ins, (split_indx - mc->mc_ki[mc->mc_top]) * ksize);
+ memcpy(ins, newkey->mv_data, ksize);
+ mp->mp_lower += sizeof(indx_t);
+ mp->mp_upper -= ksize - sizeof(indx_t);
+ } else {
+ if (x)
+ memcpy(rp->mp_ptrs, split, x * ksize);
+ ins = LEAF2KEY(rp, x, ksize);
+ memcpy(ins, newkey->mv_data, ksize);
+ memcpy(ins+ksize, split + x * ksize, rsize - x * ksize);
+ rp->mp_lower += sizeof(indx_t);
+ rp->mp_upper -= ksize - sizeof(indx_t);
+ mc->mc_ki[mc->mc_top] = x;
+ mc->mc_pg[mc->mc_top] = rp;
+ }
} else {
- if (x)
- memcpy(rp->mp_ptrs, split, x * ksize);
- ins = LEAF2KEY(rp, x, ksize);
- memcpy(ins, newkey->mv_data, ksize);
- memcpy(ins+ksize, split + x * ksize, rsize - x * ksize);
- rp->mp_lower += sizeof(indx_t);
- rp->mp_upper -= ksize - sizeof(indx_t);
- mc->mc_ki[mc->mc_top] = x;
- mc->mc_pg[mc->mc_top] = rp;
- }
- goto newsep;
- }
+ unsigned int psize, nsize, tsize;
+ int k;
+ /* Maximum free space in an empty page */
+ pmax = env->me_psize - PAGEHDRSZ;
+ if (IS_LEAF(mp))
+ nsize = mdb_leaf_size(env, newkey, newdata);
+ else
+ nsize = mdb_branch_size(env, newkey);
+ nsize += nsize & 1;
- /* For leaf pages, check the split point based on what
- * fits where, since otherwise mdb_node_add can fail.
- *
- * This check is only needed when the data items are
- * relatively large, such that being off by one will
- * make the difference between success or failure.
- *
- * It's also relevant if a page happens to be laid out
- * such that one half of its nodes are all "small" and
- * the other half of its nodes are "large." If the new
- * item is also "large" and falls on the half with
- * "large" nodes, it also may not fit.
- */
- if (IS_LEAF(mp)) {
- unsigned int psize, nsize;
- /* Maximum free space in an empty page */
- pmax = mc->mc_txn->mt_env->me_psize - PAGEHDRSZ;
- nsize = mdb_leaf_size(mc->mc_txn->mt_env, newkey, newdata);
- if ((nkeys < 20) || (nsize > pmax/16)) {
- if (newindx <= split_indx) {
- psize = nsize;
- newpos = 0;
- for (i=0; i<split_indx; i++) {
- node = NODEPTR(mp, i);
- psize += NODESIZE + NODEKSZ(node) + sizeof(indx_t);
- if (F_ISSET(node->mn_flags, F_BIGDATA))
- psize += sizeof(pgno_t);
- else
- psize += NODEDSZ(node);
- psize += psize & 1;
- if (psize > pmax) {
- if (i <= newindx) {
- split_indx = newindx;
- if (i < newindx)
- newpos = 1;
+ /* grab a page to hold a temporary copy */
+ copy = mdb_page_malloc(mc->mc_txn, 1);
+ if (copy == NULL)
+ return ENOMEM;
+ copy->mp_pgno = mp->mp_pgno;
+ copy->mp_flags = mp->mp_flags;
+ copy->mp_lower = PAGEHDRSZ;
+ copy->mp_upper = env->me_psize;
+
+ /* prepare to insert */
+ for (i=0, j=0; i<nkeys; i++) {
+ if (i == newindx) {
+ copy->mp_ptrs[j++] = 0;
+ }
+ copy->mp_ptrs[j++] = mp->mp_ptrs[i];
+ }
+
+ /* When items are relatively large the split point needs
+ * to be checked, because being off-by-one will make the
+ * difference between success or failure in mdb_node_add.
+ *
+ * It's also relevant if a page happens to be laid out
+ * such that one half of its nodes are all "small" and
+ * the other half of its nodes are "large." If the new
+ * item is also "large" and falls on the half with
+ * "large" nodes, it also may not fit.
+ *
+ * As a final tweak, if the new item goes on the last
+ * spot on the page (and thus, onto the new page), bias
+ * the split so the new page is emptier than the old page.
+ * This yields better packing during sequential inserts.
+ */
+ if (nkeys < 20 || nsize > pmax/16 || newindx >= nkeys) {
+ /* Find split point */
+ psize = 0;
+ if (newindx <= split_indx || newindx >= nkeys) {
+ i = 0; j = 1;
+ k = newindx >= nkeys ? nkeys : split_indx+1;
+ } else {
+ i = nkeys; j = -1;
+ k = split_indx-1;
+ }
+ for (; i!=k; i+=j) {
+ if (i == newindx) {
+ tsize = nsize;
+ node = NULL;
+ } else {
+ node = (MDB_node *)((char *)mp + copy->mp_ptrs[i]);
+ tsize = NODESIZE + NODEKSZ(node) + sizeof(indx_t);
+ if (IS_LEAF(mp)) {
+ if (F_ISSET(node->mn_flags, F_BIGDATA))
+ tsize += sizeof(pgno_t);
+ else
+ tsize += NODEDSZ(node);
}
- else
- split_indx = i;
- break;
+ tsize += tsize & 1;
}
- }
- } else {
- psize = nsize;
- for (i=nkeys-1; i>=split_indx; i--) {
- node = NODEPTR(mp, i);
- psize += NODESIZE + NODEKSZ(node) + sizeof(indx_t);
- if (F_ISSET(node->mn_flags, F_BIGDATA))
- psize += sizeof(pgno_t);
- else
- psize += NODEDSZ(node);
- psize += psize & 1;
- if (psize > pmax) {
- if (i >= newindx) {
- split_indx = newindx;
- newpos = 0;
- } else
- split_indx = i+1;
+ if (psize + tsize > pmax) {
+ split_indx = i + (j<0);
break;
}
+ psize += tsize;
}
+ /* special case: when the new node was on the last
+ * slot we may not have tripped the break inside the loop.
+ * In all other cases we either hit the break condition,
+ * or the original split_indx was already safe.
+ */
+ if (newindx >= nkeys && i == k)
+ split_indx = nkeys-1;
+ }
+ if (split_indx == newindx) {
+ sepkey.mv_size = newkey->mv_size;
+ sepkey.mv_data = newkey->mv_data;
+ } else {
+ node = (MDB_node *)((char *)mp + copy->mp_ptrs[split_indx]);
+ sepkey.mv_size = node->mn_ksize;
+ sepkey.mv_data = NODEKEY(node);
}
}
}
- /* First find the separating key between the split pages.
- * The case where newindx == split_indx is ambiguous; the
- * new item could go to the new page or stay on the original
- * page. If newpos == 1 it goes to the new page.
- */
- if (newindx == split_indx && newpos) {
- sepkey.mv_size = newkey->mv_size;
- sepkey.mv_data = newkey->mv_data;
- } else {
- node = NODEPTR(mp, split_indx);
- sepkey.mv_size = node->mn_ksize;
- sepkey.mv_data = NODEKEY(node);
- }
-
-newsep:
- DPRINTF(("separator is [%s]", DKEY(&sepkey)));
+ DPRINTF(("separator is %d [%s]", split_indx, DKEY(&sepkey)));
/* Copy separator key to the parent.
*/
- if (SIZELEFT(mn.mc_pg[ptop]) < mdb_branch_size(mc->mc_txn->mt_env, &sepkey)) {
+ if (SIZELEFT(mn.mc_pg[ptop]) < mdb_branch_size(env, &sepkey)) {
mn.mc_snum--;
mn.mc_top--;
did_split = 1;
@@ -7619,108 +7628,91 @@ newsep:
return rc;
for (i=0; i<mc->mc_top; i++)
mc->mc_ki[i] = mn.mc_ki[i];
- goto done;
- }
- if (IS_LEAF2(rp)) {
- goto done;
- }
-
- /* Move half of the keys to the right sibling. */
+ } else if (!IS_LEAF2(mp)) {
+ /* Move nodes */
+ mc->mc_pg[mc->mc_top] = rp;
+ i = split_indx;
+ j = 0;
+ do {
+ if (i == newindx) {
+ rkey.mv_data = newkey->mv_data;
+ rkey.mv_size = newkey->mv_size;
+ if (IS_LEAF(mp)) {
+ rdata = newdata;
+ } else
+ pgno = newpgno;
+ flags = nflags;
+ /* Update index for the new key. */
+ mc->mc_ki[mc->mc_top] = j;
+ } else {
+ node = (MDB_node *)((char *)mp + copy->mp_ptrs[i]);
+ rkey.mv_data = NODEKEY(node);
+ rkey.mv_size = node->mn_ksize;
+ if (IS_LEAF(mp)) {
+ xdata.mv_data = NODEDATA(node);
+ xdata.mv_size = NODEDSZ(node);
+ rdata = &xdata;
+ } else
+ pgno = NODEPGNO(node);
+ flags = node->mn_flags;
+ }
- /* grab a page to hold a temporary copy */
- copy = mdb_page_malloc(mc->mc_txn, 1);
- if (copy == NULL)
- return ENOMEM;
+ if (!IS_LEAF(mp) && j == 0) {
+ /* First branch index doesn't need key data. */
+ rkey.mv_size = 0;
+ }
- copy->mp_pgno = mp->mp_pgno;
- copy->mp_flags = mp->mp_flags;
- copy->mp_lower = PAGEHDRSZ;
- copy->mp_upper = mc->mc_txn->mt_env->me_psize;
- mc->mc_pg[mc->mc_top] = copy;
- for (i = j = 0; i <= nkeys; j++) {
- if (i == split_indx) {
- /* Insert in right sibling. */
- /* Reset insert index for right sibling. */
- if (i != newindx || (newpos ^ ins_new)) {
+ rc = mdb_node_add(mc, j, &rkey, rdata, pgno, flags);
+ if (rc) {
+ /* return tmp page to freelist */
+ mdb_page_free(env, copy);
+ return rc;
+ }
+ if (i == nkeys) {
+ i = 0;
j = 0;
- mc->mc_pg[mc->mc_top] = rp;
+ mc->mc_pg[mc->mc_top] = copy;
+ } else {
+ i++;
+ j++;
+ }
+ } while (i != split_indx);
+
+ nkeys = NUMKEYS(copy);
+ for (i=0; i<nkeys; i++)
+ mp->mp_ptrs[i] = copy->mp_ptrs[i];
+ mp->mp_lower = copy->mp_lower;
+ mp->mp_upper = copy->mp_upper;
+ memcpy(NODEPTR(mp, nkeys-1), NODEPTR(copy, nkeys-1),
+ env->me_psize - copy->mp_upper);
+
+ /* reset back to original page */
+ if (newindx < split_indx) {
+ mc->mc_pg[mc->mc_top] = mp;
+ if (nflags & MDB_RESERVE) {
+ node = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
+ if (!(node->mn_flags & F_BIGDATA))
+ newdata->mv_data = NODEDATA(node);
}
- }
-
- if (i == newindx && !ins_new) {
- /* Insert the original entry that caused the split. */
- rkey.mv_data = newkey->mv_data;
- rkey.mv_size = newkey->mv_size;
- if (IS_LEAF(mp)) {
- rdata = newdata;
- } else
- pgno = newpgno;
- flags = nflags;
-
- ins_new = 1;
-
- /* Update index for the new key. */
- mc->mc_ki[mc->mc_top] = j;
- } else if (i == nkeys) {
- break;
} else {
- node = NODEPTR(mp, i);
- rkey.mv_data = NODEKEY(node);
- rkey.mv_size = node->mn_ksize;
- if (IS_LEAF(mp)) {
- xdata.mv_data = NODEDATA(node);
- xdata.mv_size = NODEDSZ(node);
- rdata = &xdata;
- } else
- pgno = NODEPGNO(node);
- flags = node->mn_flags;
-
- i++;
- }
-
- if (!IS_LEAF(mp) && j == 0) {
- /* First branch index doesn't need key data. */
- rkey.mv_size = 0;
- }
-
- rc = mdb_node_add(mc, j, &rkey, rdata, pgno, flags);
- if (rc) break;
- }
-
- nkeys = NUMKEYS(copy);
- for (i=0; i<nkeys; i++)
- mp->mp_ptrs[i] = copy->mp_ptrs[i];
- mp->mp_lower = copy->mp_lower;
- mp->mp_upper = copy->mp_upper;
- memcpy(NODEPTR(mp, nkeys-1), NODEPTR(copy, nkeys-1),
- mc->mc_txn->mt_env->me_psize - copy->mp_upper);
-
- /* reset back to original page */
- if (newindx < split_indx || (!newpos && newindx == split_indx)) {
- mc->mc_pg[mc->mc_top] = mp;
- if (nflags & MDB_RESERVE) {
- node = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
- if (!(node->mn_flags & F_BIGDATA))
- newdata->mv_data = NODEDATA(node);
- }
- } else {
- mc->mc_ki[ptop]++;
- /* Make sure mc_ki is still valid.
- */
- if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
- mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
- for (i=0; i<ptop; i++) {
- mc->mc_pg[i] = mn.mc_pg[i];
- mc->mc_ki[i] = mn.mc_ki[i];
+ mc->mc_pg[mc->mc_top] = rp;
+ mc->mc_ki[ptop]++;
+ /* Make sure mc_ki is still valid.
+ */
+ if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
+ mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
+ for (i=0; i<ptop; i++) {
+ mc->mc_pg[i] = mn.mc_pg[i];
+ mc->mc_ki[i] = mn.mc_ki[i];
+ }
+ mc->mc_pg[ptop] = mn.mc_pg[ptop];
+ mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
}
- mc->mc_pg[ptop] = mn.mc_pg[ptop];
- mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
}
+ /* return tmp page to freelist */
+ mdb_page_free(env, copy);
}
- /* return tmp page to freelist */
- mdb_page_free(mc->mc_txn->mt_env, copy);
-done:
{
/* Adjust other cursors pointing to mp */
MDB_cursor *m2, *m3;
@@ -7768,6 +7760,7 @@ done:
}
}
}
+ DPRINTF(("mp left: %d, rp left: %d", SIZELEFT(mp), SIZELEFT(rp)));
return rc;
}
--
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