]> git.sur5r.net Git - openldap/commitdiff
ITS#7589 avoid wasting space in mdb_page_split
authorHoward Chu <hyc@symas.com>
Sat, 12 Oct 2013 16:34:40 +0000 (09:34 -0700)
committerHoward Chu <hyc@symas.com>
Sat, 12 Oct 2013 16:34:40 +0000 (09:34 -0700)
Also, check the split point on branch pages as well as leaf pages.

libraries/liblmdb/mdb.c

index 91a84f091f17a213d33d3d074802dc497c76251a..39635117cf93be5c7a9e78d1fdd8ecb55ef7dbbe 100644 (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)))
@@ -7440,141 +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;
 }