NextGraph
/
lmdb
mirror of https://github.com/nextgraph-org/lmdb.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

ITS#7589 avoid wasting space in mdb_page_split

Browse Source 
Also, check the split point on branch pages as well as leaf pages.
vmware
Howard Chu 11 years ago
parent 01dfb2083d
commit 310b656a2e
1 changed files with 209 additions and 216 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Show Stats Download Patch File Download Diff File
  1. 217
      libraries/liblmdb/mdb.c

217
libraries/liblmdb/mdb.c
Unescape View File

@ -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)))
@ -7440,13 +7442,9 @@ 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;
split_indx = (nkeys+1) / 2;
if (IS_LEAF2(rp)) {
char *split, *ins;
@ -7488,93 +7486,104 @@ mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno
mc->mc_ki[mc->mc_top] = x;
mc->mc_pg[mc->mc_top] = rp;
}
goto newsep;
} else {
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;
/* 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];
}
/* 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.
/* 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.
*/
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;
}
else
split_indx = i;
break;
}
*
* 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 {
psize = nsize;
for (i=nkeys-1; i>=split_indx; i--) {
node = NODEPTR(mp, i);
psize += NODESIZE + NODEKSZ(node) + sizeof(indx_t);
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))
psize += sizeof(pgno_t);
tsize += 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;
break;
}
tsize += NODEDSZ(node);
}
tsize += tsize & 1;
}
if (psize + tsize > pmax) {
split_indx = i + (j<0);
break;
}
psize += tsize;
}
/* 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.
/* 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 == split_indx && newpos) {
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 = NODEPTR(mp, split_indx);
node = (MDB_node *)((char *)mp + copy->mp_ptrs[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;
@ -7619,36 +7628,13 @@ 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. */
/* 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 = 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)) {
j = 0;
} else if (!IS_LEAF2(mp)) {
/* Move nodes */
mc->mc_pg[mc->mc_top] = rp;
}
}
if (i == newindx && !ins_new) {
/* Insert the original entry that caused the split. */
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)) {
@ -7656,15 +7642,10 @@ newsep:
} 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);
node = (MDB_node *)((char *)mp + copy->mp_ptrs[i]);
rkey.mv_data = NODEKEY(node);
rkey.mv_size = node->mn_ksize;
if (IS_LEAF(mp)) {
@ -7674,8 +7655,6 @@ newsep:
} else
pgno = NODEPGNO(node);
flags = node->mn_flags;
i++;
}
if (!IS_LEAF(mp) && j == 0) {
@ -7684,8 +7663,20 @@ newsep:
}
rc = mdb_node_add(mc, j, &rkey, rdata, pgno, flags);
if (rc) break;
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] = copy;
} else {
i++;
j++;
}
} while (i != split_indx);
nkeys = NUMKEYS(copy);
for (i=0; i<nkeys; i++)
@ -7693,10 +7684,10 @@ newsep:
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);
env->me_psize - copy->mp_upper);
/* reset back to original page */
if (newindx < split_indx || (!newpos && newindx == split_indx)) {
if (newindx < split_indx) {
mc->mc_pg[mc->mc_top] = mp;
if (nflags & MDB_RESERVE) {
node = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
@ -7704,6 +7695,7 @@ newsep:
newdata->mv_data = NODEDATA(node);
}
} else {
mc->mc_pg[mc->mc_top] = rp;
mc->mc_ki[ptop]++;
/* Make sure mc_ki is still valid.
*/
@ -7717,10 +7709,10 @@ newsep:
mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
}
}
/* return tmp page to freelist */
mdb_page_free(mc->mc_txn->mt_env, copy);
done:
mdb_page_free(env, copy);
}
{
/* 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;
}

Write Preview
Loading…
Cancel
Save