stasis-bLSM/diskTreeComponent.cpp

/*
 * diskTreeComponent.cpp
 *
 * Copyright 2010-2012 Yahoo! Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 *  Created on: Feb 18, 2010
 *      Author: sears
 */

#include <string.h>
#include <assert.h>
#include <math.h>
#include <ctype.h>

#include "merger.h"
#include "diskTreeComponent.h"
#include "regionAllocator.h"

#include "mergeStats.h"
#include <stasis/transactional.h>
#include <stasis/page.h>
#include <stasis/page/slotted.h>

/////////////////////////////////////////////////////////////////
// LOGTREE implementation
/////////////////////////////////////////////////////////////////

//LSM_ROOT_PAGE

const int64_t diskTreeComponent::internalNodes::DEPTH = 0;      //in root this is the slot num where the DEPTH (of tree) is stored
const int64_t diskTreeComponent::internalNodes::COMPARATOR = 1; //in root this is the slot num where the COMPARATOR id is stored
const int64_t diskTreeComponent::internalNodes::FIRST_SLOT = 2; //this is the first unused slot in all index pages
const ssize_t diskTreeComponent::internalNodes::root_rec_size = sizeof(int64_t);
const int64_t diskTreeComponent::internalNodes::PREV_LEAF = 0; //pointer to prev leaf page
const int64_t diskTreeComponent::internalNodes::NEXT_LEAF = 1; //pointer to next leaf page

recordid diskTreeComponent::get_root_rid() { return ltree->get_root_rec(); }
recordid diskTreeComponent::get_datapage_allocator_rid() { return ltree->get_datapage_alloc()->header_rid(); }
recordid diskTreeComponent::get_internal_node_allocator_rid() { return ltree->get_internal_node_alloc()->header_rid(); }



void diskTreeComponent::force(int xid) {
  ltree->get_datapage_alloc()->force_regions(xid);
  ltree->get_internal_node_alloc()->force_regions(xid);
}
void diskTreeComponent::dealloc(int xid) {
  ltree->get_datapage_alloc()->dealloc_regions(xid);
  ltree->get_internal_node_alloc()->dealloc_regions(xid);
}
void diskTreeComponent::list_regions(int xid, pageid_t *internal_node_region_length, pageid_t *internal_node_region_count, pageid_t **internal_node_regions,
          pageid_t *datapage_region_length, pageid_t *datapage_region_count, pageid_t **datapage_regions) {
  *internal_node_regions = ltree->get_internal_node_alloc()->list_regions(xid, internal_node_region_length, internal_node_region_count);
  *datapage_regions      = ltree->get_datapage_alloc()     ->list_regions(xid, datapage_region_length, datapage_region_count);
}


void diskTreeComponent::writes_done() {
  if(dp) {
    ((mergeStats*)stats)->wrote_datapage(dp);
    dp->writes_done();
    delete dp;
    dp = 0;
  }
}

int diskTreeComponent::insertTuple(int xid, datatuple *t)
{
  if(bloom_filter) {
    bloom_filter_insert(bloom_filter, (const char*)t->strippedkey(), t->strippedkeylen());
  }
  int ret = 0; // no error.
  if(dp==0) {
    dp = insertDataPage(xid, t);
    //    stats->stats_num_datapages_out++;
  } else if(!dp->append(t)) {
    //    stats->stats_bytes_out_with_overhead += (PAGE_SIZE * dp->get_page_count());
    ((mergeStats*)stats)->wrote_datapage(dp);
    dp->writes_done();
    delete dp;
    dp = insertDataPage(xid, t);
    //    stats->stats_num_datapages_out++;
  }
  return ret;
}

DataPage* diskTreeComponent::insertDataPage(int xid, datatuple *tuple) {
    //create a new data page -- either the last region is full, or the last data page doesn't want our tuple.  (or both)

    DataPage * dp = 0;
    int count = 0;
    while(dp==0)
    {
      dp = new DataPage(xid, datapage_size, ltree->get_datapage_alloc());

        //insert the record into the data page
        if(!dp->append(tuple))
        {
            // the last datapage must have not wanted the tuple, and then this datapage figured out the region is full.
          ((mergeStats*)stats)->wrote_datapage(dp);
            dp->writes_done();
            delete dp;
            dp = 0;
            assert(count == 0); // only retry once.
            count ++;
        }
    }


    ltree->appendPage(xid,
                        tuple->strippedkey(),
                        tuple->strippedkeylen(),
                        dp->get_start_pid()
                        );


    //return the datapage
    return dp;
}

datatuple * diskTreeComponent::findTuple(int xid, datatuple::key_t key, size_t keySize)
{
    datatuple * tup=0;

    if(bloom_filter) {
      if(!bloom_filter_lookup(bloom_filter, (const char*)key, keySize)) {
        return NULL;
      }
    }
    
    //find the datapage
    pageid_t pid = ltree->findPage(xid, (byte*)key, keySize);

    if(pid!=-1)
    {
        DataPage * dp = new DataPage(xid, 0, pid);
        dp->recordRead(key, keySize, &tup);
        delete dp;
    }
    return tup;
}

recordid diskTreeComponent::internalNodes::create(int xid) {

  pageid_t root = internal_node_alloc->alloc_extent(xid, 1);
  DEBUG("Root = %lld\n", root);
  recordid ret = { root, 0, 0 };

  Page *p = loadPage(xid, ret.page);

  //initialize root node
  stasis_page_slotted_initialize_page(p);
  recordid tmp  = stasis_record_alloc_begin(xid, p, root_rec_size);
  stasis_record_alloc_done(xid,p,tmp);

  assert(tmp.page == ret.page
         && tmp.slot == DEPTH
         && tmp.size == root_rec_size);

  int64_t zero = 0;
  assert(sizeof(zero) == root_rec_size);
  stasis_record_write(xid, p, tmp, (byte*)&zero);

  tmp = stasis_record_alloc_begin(xid, p, root_rec_size);
  stasis_record_alloc_done(xid,p,tmp);

  assert(tmp.page == ret.page
         && tmp.slot == COMPARATOR
         && tmp.size == root_rec_size);

  stasis_record_write(xid, p, tmp, (byte*)&zero);

  stasis_page_lsn_write(xid, p, internal_node_alloc->get_lsn(xid));

  releasePage(p);

  root_rec = ret;

  return ret;
}

void diskTreeComponent::internalNodes::writeNodeRecord(int xid, Page * p, recordid & rid,
                              const byte *key, size_t keylen, pageid_t ptr) {
  DEBUG("writenoderecord:\tp->id\t%lld\tkey:\t%s\tkeylen: %d\tval_page\t%lld\n",
        p->id, datatuple::key_to_str(key).c_str(), keylen, ptr);
  indexnode_rec *nr = (indexnode_rec*)stasis_record_write_begin(xid, p, rid);
  nr->ptr = ptr;
  memcpy(nr+1, key, keylen);
  stasis_record_write_done(xid, p, rid, (byte*)nr);
  stasis_page_lsn_write(xid, p, internal_node_alloc->get_lsn(xid));
}

void diskTreeComponent::internalNodes::initializeNodePage(int xid, Page *p) {
  stasis_page_slotted_initialize_page(p);
  recordid reserved1 = stasis_record_alloc_begin(xid, p, sizeof(indexnode_rec));
  stasis_record_alloc_done(xid, p, reserved1);
  recordid reserved2 = stasis_record_alloc_begin(xid, p, sizeof(indexnode_rec));
  stasis_record_alloc_done(xid, p, reserved2);
}


recordid diskTreeComponent::internalNodes::appendPage(int xid,
                             const byte *key, size_t keySize, pageid_t val_page) {
  recordid tree = root_rec;

  Page *p = loadPage(xid, tree.page);

  tree.slot = DEPTH;
  tree.size = 0;

  readlock(p->rwlatch,0);
  const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid, p, tree);
  int64_t depth = *((int64_t*)nr);
  stasis_record_read_done(xid, p, tree, (const byte*)nr);
  unlock(p->rwlatch);
  if(lastLeaf == -1) {
    lastLeaf = findLastLeaf(xid, p, depth);
  }

  Page *lastLeafPage;

  if(lastLeaf != tree.page) {
    lastLeafPage= loadPage(xid, lastLeaf);
  } else {
    lastLeafPage = p;
  }

  writelock(lastLeafPage->rwlatch, 0);

  recordid ret = stasis_record_alloc_begin(xid, lastLeafPage,
                                           sizeof(indexnode_rec)+keySize);

  if(ret.size == INVALID_SLOT) {
    unlock(lastLeafPage->rwlatch);
    if(lastLeafPage->id != p->id) {  // is the root the last leaf page?
      assert(lastLeaf != tree.page);
      releasePage(lastLeafPage); // don't need that page anymore...
      lastLeafPage = 0;
    }
    // traverse down the root of the tree.

    tree.slot = 0;

    assert(tree.page == p->id);

    ret = appendInternalNode(xid, p, depth, key, keySize, val_page);

    if(ret.size == INVALID_SLOT) {
      DEBUG("Need to split root; depth = %d\n", depth);

      pageid_t child = internal_node_alloc->alloc_extent(xid, 1);
      slotid_t numslots = stasis_record_last(xid, p).slot+1;
      {
        Page *lc = loadPage(xid, child);

        initializeNodePage(xid, lc);

        //creates a copy of the root page records in the
        //newly allocated child page
        recordid rid;
        rid.page = p->id;
        // XXX writelock lc here?  no need, since it's not installed in the tree yet
        for(rid.slot = FIRST_SLOT; rid.slot < numslots; rid.slot++) {
          //read the record from the root page
          rid.size = stasis_record_length_read(xid, p, rid);
          const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid, p, rid);
          recordid cnext = stasis_record_alloc_begin(xid, lc,rid.size);

          assert(rid.slot == cnext.slot);
          assert(cnext.size != INVALID_SLOT);

          stasis_record_alloc_done(xid, lc, cnext);
          stasis_record_write(xid, lc, cnext, (byte*)nr);
          stasis_record_read_done(xid, p, rid, (const byte*)nr);
        }

        if(!depth) {
            lastLeaf = lc->id;
            pageid_t tmpid = -1;
            recordid rid = { lc->id, PREV_LEAF, root_rec_size };
            stasis_record_write(xid, lc, rid, (byte*)&tmpid);
            rid.slot = NEXT_LEAF;
            stasis_record_write(xid, lc, rid, (byte*)&tmpid);
        }

        stasis_page_lsn_write(xid, lc, internal_node_alloc->get_lsn(xid));
        releasePage(lc);
      } // lc is now out of scope.

      // deallocate old entries, and update pointer on parent node.
      // NOTE: stasis_record_free call goes to slottedFree in slotted.c
      // this function only reduces the numslots when you call it
      // with the last slot. so thats why i go backwards here.
      DEBUG("slots %d (%d) keysize=%lld\n", (int)last_slot+1, (int)FIRST_SLOT+1, (long long int)keySize);
      assert(numslots >= FIRST_SLOT+1);

      writelock(p->rwlatch,0);
      // Note that we leave the first slot in place.
      for(int i = numslots-1; i>FIRST_SLOT; i--) {
        recordid tmp_rec= {p->id, i, INVALID_SIZE};
        stasis_record_free(xid, p, tmp_rec);
      }
      recordid pFirstSlot = stasis_record_last(xid, p);
      assert(pFirstSlot.slot == FIRST_SLOT);
      //TODO: could change with stasis_slotted_page_initialize(...);
      // TODO: fsck?

      // reinsert first.

      indexnode_rec *nr
          = (indexnode_rec*)stasis_record_write_begin(xid, p, pFirstSlot);

      // don't overwrite key...
      nr->ptr = child;
      stasis_record_write_done(xid,p,pFirstSlot,(byte*)nr);

      //update the depth info at the root
      depth ++;
      recordid depth_rid = { p->id, DEPTH, root_rec_size };
      stasis_record_write(xid, p, depth_rid, (byte*)(&depth));
      unlock(p->rwlatch);
      assert(tree.page == p->id);
      ret = appendInternalNode(xid, p, depth, key, keySize, val_page);

      assert(ret.size != INVALID_SLOT);

    } else {
      DEBUG("Appended new internal node tree depth = %lld key = %s\n",
            depth, datatuple::key_to_str(key).c_str());
    }

    lastLeaf = ret.page;
    DEBUG("lastleaf is %lld\n", lastLeaf);

  } else {
    // write the new value to an existing page
    DEBUG("Writing %s\t%d to existing page# %lld\n", datatuple::key_to_str(key).c_str(),
          val_page, lastLeafPage->id);
    stasis_record_alloc_done(xid, lastLeafPage, ret);

    writeNodeRecord(xid, lastLeafPage, ret, key, keySize, val_page);
    unlock(lastLeafPage->rwlatch);

    if(lastLeafPage->id != p->id) {
      assert(lastLeaf != tree.page);
      releasePage(lastLeafPage);
    }
  }

  stasis_page_lsn_write(xid, p, internal_node_alloc->get_lsn(xid));

  releasePage(p);

  return ret;
}

diskTreeComponent::internalNodes::internalNodes(int xid, pageid_t internal_region_size, pageid_t datapage_region_size, pageid_t datapage_size)
: lastLeaf(-1),
  internal_node_alloc(new RegionAllocator(xid, internal_region_size)),
  datapage_alloc(new RegionAllocator(xid, datapage_region_size))
{ create(xid); }

diskTreeComponent::internalNodes::internalNodes(int xid, recordid root, recordid internal_node_state, recordid datapage_state)
: lastLeaf(-1),
  root_rec(root),
  internal_node_alloc(new RegionAllocator(xid, internal_node_state)),
  datapage_alloc(new RegionAllocator(xid, datapage_state))
{ }

diskTreeComponent::internalNodes::~internalNodes() {
  delete internal_node_alloc;
  delete datapage_alloc;
}

/* adding pages:

  1) Try to append value to lsmTreeState->lastLeaf

  2) If that fails, traverses down the root of the tree, split pages while
     traversing back up.

  3) Split is done by adding new page at end of row (no key
     redistribution), except at the root, where root contents are
     pushed into the first page of the next row, and a new path from root to
     leaf is created starting with the root's immediate second child.

*/

recordid diskTreeComponent::internalNodes::appendInternalNode(int xid, Page *p,
                                     int64_t depth,
                                     const byte *key, size_t key_len,
                                     pageid_t val_page) {

  assert(p->pageType == SLOTTED_PAGE);

  recordid ret;

  if(!depth) {
    // leaf node.
    writelock(p->rwlatch, 0);
    ret = stasis_record_alloc_begin(xid, p, sizeof(indexnode_rec)+key_len);
    if(ret.size != INVALID_SLOT) {
      stasis_record_alloc_done(xid, p, ret);
      writeNodeRecord(xid,p,ret,key,key_len,val_page);
      stasis_page_lsn_write(xid, p, internal_node_alloc->get_lsn(xid)); // XXX remove this (writeNodeRecord calls it for us)
    }
    unlock(p->rwlatch);
  } else {
    
    // recurse
    recordid last_rid = stasis_record_last(xid, p);

    assert(last_rid.slot >= FIRST_SLOT); // there should be no empty nodes
    const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid, p, last_rid);

    pageid_t child_id = nr->ptr;
    stasis_record_read_done(xid, p, last_rid, (const byte*)nr);
    nr = 0;
    {
      Page *child_page = loadPage(xid, child_id);
      ret = appendInternalNode(xid, child_page, depth-1, key, key_len,
                               val_page);
      releasePage(child_page);
    }

    if(ret.size == INVALID_SLOT) { // subtree is full; split
      ret = stasis_record_alloc_begin(xid, p, sizeof(indexnode_rec)+key_len);
      DEBUG("keylen %d\tnumslots %d for page id %lld ret.size %lld  prv rec len %d\n",
            key_len,
            stasis_record_last(xid, p).slot+1,
            p->id,
            ret.size,
            readRecordLength(xid, p, slot));
      if(ret.size != INVALID_SLOT) {
        writelock(p->rwlatch, 0); // XXX we hold this longer than necessary.  push latching into buildPathToLeaf().
        stasis_record_alloc_done(xid, p, ret);
        ret = buildPathToLeaf(xid, ret, p, depth, key, key_len, val_page);
        unlock(p->rwlatch);
        DEBUG("split tree rooted at %lld, wrote value to {%d %d %lld}\n",
              p->id, ret.page, ret.slot, ret.size);
      } else {
          // ret is NULLRID; this is the root of a full tree. Return
          // NULLRID to the caller.
      }
    } else {
      // we inserted the value in to a subtree rooted here.
    }
  }
  return ret;
}

recordid diskTreeComponent::internalNodes::buildPathToLeaf(int xid, recordid root, Page *root_p,
                                  int64_t depth, const byte *key, size_t key_len,
                                  pageid_t val_page) {

  // root is the recordid on the root page that should point to the
  // new subtree.
  assert(depth);
  DEBUG("buildPathToLeaf(depth=%lld) (lastleaf=%lld) called\n",depth, lastLeaf);

  pageid_t child = internal_node_alloc->alloc_extent(xid, 1);
  DEBUG("new child = %lld internal? %lld\n", child, depth-1);

  Page *child_p = loadPage(xid, child);
  initializeNodePage(xid, child_p);

  recordid ret;

  if(depth-1) {
    // recurse: the page we just allocated is not a leaf.
    recordid child_rec = stasis_record_alloc_begin(xid, child_p, sizeof(indexnode_rec)+key_len);
    assert(child_rec.size != INVALID_SLOT);
    stasis_record_alloc_done(xid, child_p, child_rec);

    ret = buildPathToLeaf(xid, child_rec, child_p, depth-1, key, key_len,
                          val_page);

    releasePage(child_p);

  } else {
    // set leaf

    // backward link. records were alloced by page initialization
    recordid prev_leaf_rid = { child_p->id, PREV_LEAF, root_rec_size };
    stasis_record_write(xid, child_p, prev_leaf_rid, (byte*)&lastLeaf);

    // forward link (initialize to -1)
    pageid_t tmp_pid = -1;
    recordid next_leaf_rid = { child_p->id, NEXT_LEAF, root_rec_size };
    stasis_record_write(xid, child_p, next_leaf_rid, (byte*)&tmp_pid);

    recordid leaf_rec = stasis_record_alloc_begin(xid, child_p,
                                     sizeof(indexnode_rec)+key_len);

    assert(leaf_rec.slot == FIRST_SLOT);

    stasis_record_alloc_done(xid, child_p, leaf_rec);
    writeNodeRecord(xid,child_p,leaf_rec,key,key_len,val_page);

    ret = leaf_rec;

    stasis_page_lsn_write(xid, child_p, internal_node_alloc->get_lsn(xid));
    releasePage(child_p);
    if(lastLeaf != -1 && lastLeaf != root_rec.page) {
      // install forward link in previous page
      Page *lastLeafP = loadPage(xid, lastLeaf);
      writelock(lastLeafP->rwlatch,0);
      recordid last_next_leaf_rid = {lastLeaf, NEXT_LEAF, root_rec_size };
      stasis_record_write(xid,lastLeafP,last_next_leaf_rid,(byte*)&child);
      stasis_page_lsn_write(xid, lastLeafP, internal_node_alloc->get_lsn(xid));
      unlock(lastLeafP->rwlatch);
      releasePage(lastLeafP);
    }

    DEBUG("%lld <-> %lld\n", lastLeaf, child);
  }

  // Crucially, this happens *after* the recursion.  Therefore, we can query the
  // tree with impunity while the leaf is being built and don't have to worry
  // about dangling pointers to pages that are in the process of being allocated.

  // XXX set bool on recursive call, and only grab the write latch at the first level of recursion.
  writeNodeRecord(xid, root_p, root, key, key_len, child);

  return ret;

}

/**
 * Traverse from the root of the page to the right most leaf (the one
 * with the higest base key value).
 **/
pageid_t diskTreeComponent::internalNodes::findLastLeaf(int xid, Page *root, int64_t depth) {
  if(!depth) {
    DEBUG("Found last leaf = %lld\n", root->id);
    return root->id;
  } else {
    readlock(root->rwlatch,0);
    recordid last_rid = stasis_record_last(xid, root);

    const indexnode_rec * nr = (const indexnode_rec*)stasis_record_read_begin(xid, root, last_rid);
    pageid_t ptr = nr->ptr;
    stasis_record_read_done(xid, root, last_rid, (const byte*)nr);
    unlock(root->rwlatch);

    Page *p = loadPage(xid, ptr);
    pageid_t ret = findLastLeaf(xid,p,depth-1);
    releasePage(p);

    return ret;
  }
}

/**
 *  Traverse from the root of the tree to the left most (lowest valued
 *  key) leaf.
 */
pageid_t diskTreeComponent::internalNodes::findFirstLeaf(int xid, Page *root, int64_t depth) {

  if(!depth) { //if depth is 0, then returns the id of the page
    return root->id;
  } else {
    recordid rid = {root->id, FIRST_SLOT, 0};

    readlock(root->rwlatch,0);
    const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid, root, rid);
    pageid_t ptr = nr->ptr;
    unlock(root->rwlatch);
    Page *p = loadPage(xid, ptr);
    pageid_t ret = findFirstLeaf(xid,p,depth-1);
    releasePage(p);
    return ret;
  }
}


pageid_t diskTreeComponent::internalNodes::findPage(int xid, const byte *key, size_t keySize) {

  Page *p = loadPage(xid, root_rec.page);

  recordid depth_rid = {p->id, DEPTH, 0};
  readlock(p->rwlatch,0);
  const int64_t * depthp = (const int64_t*)stasis_record_read_begin(xid, p, depth_rid);
  int64_t depth = *depthp;
  stasis_record_read_done(xid, p, depth_rid, (const byte*)depthp);
  unlock(p->rwlatch);

  recordid rid = lookup(xid, p, depth, key, keySize);

  pageid_t ret = lookupLeafPageFromRid(xid,rid);
  releasePage(p);

  return ret;

}

pageid_t diskTreeComponent::internalNodes::lookupLeafPageFromRid(int xid, recordid rid) {

  pageid_t pid = -1;
  if(rid.page != NULLRID.page || rid.slot != NULLRID.slot) {
    Page * p2 = loadPage(xid, rid.page);
    readlock(p2->rwlatch,0);
    const indexnode_rec * nr = (const indexnode_rec*)stasis_record_read_begin(xid, p2, rid);
    pid = nr->ptr;
    stasis_record_read_done(xid, p2, rid, (const byte*)nr);
    unlock(p2->rwlatch);
    releasePage(p2);
  }
  return pid;
}

recordid diskTreeComponent::internalNodes::lookup(int xid,
                            Page *node,
                            int64_t depth,
                            const byte *key, size_t keySize ) {

  //DEBUG("lookup: pid %lld\t depth %lld\n", node->id, depth);
  readlock(node->rwlatch,0);
  slotid_t numslots = stasis_record_last(xid, node).slot + 1;

  if(numslots == FIRST_SLOT) {
    unlock(node->rwlatch);
    return NULLRID;
  }
  assert(numslots > FIRST_SLOT);

  // don't need to compare w/ first item in tree, since we need to position ourselves at the the max tree value <= key.
  // positioning at FIRST_SLOT puts us "before" the first value
  int match = FIRST_SLOT; // (so match is now < key)
  recordid rid;
  rid.page = node->id;
  rid.size = 0;
  for(rid.slot = FIRST_SLOT+1; rid.slot < numslots; rid.slot++) {
    rid.size = stasis_record_length_read(xid, node, rid);

    const indexnode_rec *rec = (const indexnode_rec*)stasis_record_read_begin(xid,node,rid);
    int cmpval = datatuple::compare((datatuple::key_t) (rec+1), rid.size-sizeof(*rec),
                                    (datatuple::key_t) key, keySize);
    stasis_record_read_done(xid,node,rid,(const byte*)rec);

    // key of current node is too big; there can be no matches under it.
    if(cmpval>0) break;

    match = rid.slot; // only increment match after comparing with the current node.
  }
  rid.slot = match;
  rid.size = 0;

  if(depth) {
    const indexnode_rec* nr = (const indexnode_rec*)stasis_record_read_begin(xid, node, rid);
    pageid_t child_id = nr->ptr;
    stasis_record_read_done(xid, node, rid, (const byte*)nr);

    unlock(node->rwlatch);
    Page* child_page = loadPage(xid, child_id);
    recordid ret = lookup(xid,child_page,depth-1,key,keySize);

    releasePage(child_page);
    return ret;
  } else {
    unlock(node->rwlatch);
    recordid ret = {node->id, match, keySize};
    return ret;
  }
}

void diskTreeComponent::internalNodes::print_tree(int xid) {
  Page *p = loadPage(xid, root_rec.page);
  readlock(p->rwlatch,0);
  recordid depth_rid = {p->id, DEPTH, 0};
  const indexnode_rec *depth_nr = (const indexnode_rec*)stasis_record_read_begin(xid, p , depth_rid);

  int64_t depth = depth_nr->ptr;
  stasis_record_read_done(xid,p,depth_rid,(const byte*)depth_nr);

  print_tree(xid, root_rec.page, depth); // XXX expensive latching!

  unlock(p->rwlatch);
  releasePage(p);

}

void diskTreeComponent::internalNodes::print_tree(int xid, pageid_t pid, int64_t depth) {

  Page *node = loadPage(xid, pid);
  readlock(node->rwlatch,0);

  slotid_t numslots = stasis_record_last(xid,node).slot + 1;

  printf("page_id:%lld\tnum_slots:%d\t\n", node->id, numslots);

  if(numslots == FIRST_SLOT) {
    return;
  }

  assert(numslots > FIRST_SLOT);

  recordid rid = { node->id, 0, 0 };

  if(depth) {
    printf("\tnot_leaf\n");

    for(int i = FIRST_SLOT; i < numslots; i++) {
      rid.slot = i;
      const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid,node,rid);
      printf("\tchild_page_id:%lld\tkey:%s\n", nr->ptr,
             datatuple::key_to_str((byte*)(nr+1)).c_str());
      stasis_record_read_done(xid, node, rid, (const byte*)nr);
    }

    for(int i = FIRST_SLOT; i < numslots; i++) {
      rid.slot = i;
      const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid,node,rid);
      print_tree(xid, nr->ptr, depth-1);
      stasis_record_read_done(xid, node, rid, (const byte*)nr);
    }

  } else {
    printf("\tis_leaf\t\n");

    rid.slot = FIRST_SLOT;
    const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid,node,rid);
    printf("\tdata_page_id:%lld\tkey:%s\n", nr->ptr,
           datatuple::key_to_str((byte*)(nr+1)).c_str());
    stasis_record_read_done(xid, node, rid, (const byte*)nr);

    printf("\t...\n");

    rid.slot= numslots - 1;
    nr = (const indexnode_rec*)stasis_record_read_begin(xid,node,rid);
    printf("\tdata_page_id:%lld\tkey:%s\n", nr->ptr,
           datatuple::key_to_str((byte*)(nr+1)).c_str());
    stasis_record_read_done(xid, node, rid, (const byte*)nr);
}
  unlock(node->rwlatch);
  releasePage(node);
}

/////////////////////////////////////////////////
//diskTreeComponentIterator implementation
/////////////////////////////////////////////////

diskTreeComponent::internalNodes::iterator::iterator(int xid, RegionAllocator* ro_alloc, recordid root) {
  ro_alloc_ = ro_alloc;
  if(root.page == 0 && root.slot == 0 && root.size == -1) abort();
  p = ro_alloc_->load_page(xid,root.page);

  DEBUG("ROOT_REC_SIZE %d\n", diskTreeComponent::internalNodes::root_rec_size);
  recordid rid = {p->id, diskTreeComponent::internalNodes::DEPTH, diskTreeComponent::internalNodes::root_rec_size};

  readlock(p->rwlatch, 0);
  const indexnode_rec* nr = (const indexnode_rec*)stasis_record_read_begin(xid,p, rid);

  int64_t depth = nr->ptr;
  justOnePage = (depth == 0);
  DEBUG("DEPTH = %lld\n", depth);
  stasis_record_read_done(xid,p,rid,(const byte*)nr);
  // NOTE: The root page is not append only.  We need to hold onto
  // this latch throughout the iteration to protect ourselves from
  // root tree splits.  For multi-level trees, this is not the case,
  // as everything below the root is append-only, so we can release
  // and reacquire the latches if need be.
  if(!justOnePage) unlock(p->rwlatch);

  pageid_t leafid = diskTreeComponent::internalNodes::findFirstLeaf(xid, p, depth);
  if(leafid != root.page) {

    releasePage(p);
    p = ro_alloc_->load_page(xid,leafid);
    assert(depth != 0);
  } else {
    assert(depth == 0);
  }

  {
    // Position just before the first slot.
    // The first call to next() will increment us to the first slot, or return NULL.
    recordid rid = { p->id, diskTreeComponent::internalNodes::FIRST_SLOT-1, 0};
    current = rid;
  }

  DEBUG("keysize = %d, slot = %d\n", keySize, current.slot);
  xid_ = xid;
  done = false;
  t = 0;
  if(!justOnePage) readlock(p->rwlatch,0);
}

diskTreeComponent::internalNodes::iterator::iterator(int xid, RegionAllocator* ro_alloc, recordid root, const byte* key, len_t keylen) {
  if(root.page == NULLRID.page && root.slot == NULLRID.slot) abort();
  ro_alloc_ = ro_alloc;
  p = ro_alloc_->load_page(xid,root.page);

  recordid rid = {p->id, diskTreeComponent::internalNodes::DEPTH, diskTreeComponent::internalNodes::root_rec_size};


  readlock(p->rwlatch,0);
  const indexnode_rec* nr = (const indexnode_rec*)stasis_record_read_begin(xid,p,rid);
  int64_t depth = nr->ptr;
  justOnePage = (depth==0);
  stasis_record_read_done(xid,p,rid,(const byte*)nr);

  recordid lsm_entry_rid = diskTreeComponent::internalNodes::lookup(xid,p,depth,key,keylen);

  if(lsm_entry_rid.page == NULLRID.page && lsm_entry_rid.slot == NULLRID.slot) {
    unlock(p->rwlatch);
    releasePage(p);
    p = NULL;
    done = true;
  } else {

    if(!justOnePage) unlock(p->rwlatch);

    assert(lsm_entry_rid.size != INVALID_SLOT);

    if(root.page != lsm_entry_rid.page)
    {
      releasePage(p);
      p = ro_alloc->load_page(xid,lsm_entry_rid.page);
      assert(!justOnePage);
    } else {
      assert(justOnePage);
    }

    done = false;
    current.page = lsm_entry_rid.page;
    current.slot = lsm_entry_rid.slot-1;  // this is current rid, which is one less than the first thing next will return (so subtract 1)
    current.size = lsm_entry_rid.size;

    xid_ = xid;

    DEBUG("diskTreeComponentIterator: index root %lld index page %lld data page %lld key %s\n", root.page, current.page, rec->ptr, key);
    DEBUG("entry = %s key = %s\n", (char*)(rec+1), (char*)key);

    if(!justOnePage) readlock(p->rwlatch,0);
  }
  t = 0; // must be zero so free() doesn't croak.
}

/**
 * move to the next page
 **/
int diskTreeComponent::internalNodes::iterator::next()
{
  if(done) return 0;

  current = stasis_record_next(xid_, p, current);

  if(current.size == INVALID_SLOT) {

    recordid next_leaf_rid = {p->id, diskTreeComponent::internalNodes::NEXT_LEAF,0};
    const indexnode_rec *nr = (const indexnode_rec*)stasis_record_read_begin(xid_, p, next_leaf_rid);
    pageid_t next_rec = nr->ptr;
    stasis_record_read_done(xid_,p,next_leaf_rid,(const byte*)nr);

    unlock(p->rwlatch);
    releasePage(p);

    DEBUG("done with page %lld next = %lld\n", p->id, next_rec.ptr);

    if(next_rec != -1 && ! justOnePage) {
      p = ro_alloc_->load_page(xid_, next_rec);
      readlock(p->rwlatch,0);
      current.page = next_rec;
      current.slot = 2;
      current.size = stasis_record_length_read(xid_, p, current);
    } else {
      p = 0;
      current.size = INVALID_SLOT;
    }

  }

  if(current.size != INVALID_SLOT) {
    if(t != NULL) { free(t); t = NULL; }

    t = (indexnode_rec*)malloc(current.size);
    const byte * buf = stasis_record_read_begin(xid_, p, current);
    memcpy(t, buf, current.size);
    stasis_record_read_done(xid_, p, current, buf);

    return 1;
  } else {
    assert(!p);
    if(t != NULL) { free(t); t = NULL; }
    return 0;
  }
}

void diskTreeComponent::internalNodes::iterator::close() {

  if(p) {
    unlock(p->rwlatch);
    releasePage(p);
    p = NULL;
  }
  if(t) {
    free(t);
    t = NULL;
  }
}


/////////////////////////////////////////////////////////////////////
// tree iterator implementation
/////////////////////////////////////////////////////////////////////

void diskTreeComponent::iterator::init_iterators(datatuple * key1, datatuple * key2) {
    assert(!key2); // unimplemented
    if(tree_.size == INVALID_SIZE) {
        lsmIterator_ = NULL;
    } else {
        if(key1) {
            lsmIterator_ = new diskTreeComponent::internalNodes::iterator(-1, ro_alloc_, tree_, key1->strippedkey(), key1->strippedkeylen());
        } else {
            lsmIterator_ = new diskTreeComponent::internalNodes::iterator(-1, ro_alloc_, tree_);
        }
    }
  }

diskTreeComponent::iterator::iterator(diskTreeComponent::internalNodes *tree, mergeManager * mgr, double target_progress_delta, bool * flushing) :
    ro_alloc_(new RegionAllocator()),
    tree_(tree ? tree->get_root_rec() : NULLRID),
    mgr_(mgr),
    target_progress_delta_(target_progress_delta),
    flushing_(flushing)
{
    init_iterators(NULL, NULL);
    init_helper(NULL);
}

diskTreeComponent::iterator::iterator(diskTreeComponent::internalNodes *tree, datatuple* key) :
    ro_alloc_(new RegionAllocator()),
    tree_(tree ? tree->get_root_rec() : NULLRID),
    mgr_(NULL),
    target_progress_delta_(0.0),
    flushing_(NULL)
{
    init_iterators(key,NULL);
    init_helper(key);

}

diskTreeComponent::iterator::~iterator() {
  if(lsmIterator_) {
      lsmIterator_->close();
      delete lsmIterator_;
  }

  delete curr_page;
  curr_page = 0;

  delete ro_alloc_;
}

void diskTreeComponent::iterator::init_helper(datatuple* key1)
{
    if(!lsmIterator_)
    {
        DEBUG("treeIterator:\t__error__ init_helper():\tnull lsmIterator_");
        curr_page = 0;
        dp_itr = 0;
    }
    else
    {
        if(lsmIterator_->next() == 0)
        {
            DEBUG("diskTreeIterator:\t__error__ init_helper():\tlogtreeIteratr::next returned 0." );
            curr_page = 0;
            dp_itr = 0;
        }
        else
        {
            pageid_t * pid_tmp;
            pageid_t ** hack = &pid_tmp;
            lsmIterator_->value((byte**)hack);

            curr_pageid = *pid_tmp;
            curr_page = new DataPage(-1, ro_alloc_, curr_pageid);

            DEBUG("opening datapage iterator %lld at key %s\n.", curr_pageid, key1 ? (char*)key1->key() : "NULL");
            dp_itr = new DPITR_T(curr_page, key1);
        }

    }
}

datatuple * diskTreeComponent::iterator::next_callerFrees()
{
    if(!this->lsmIterator_) { return NULL; }

    if(dp_itr == 0)
        return 0;

    datatuple* readTuple = dp_itr->getnext();


    if(!readTuple)
    {
        delete dp_itr;
        dp_itr = 0;
        delete curr_page;
        curr_page = 0;

        if(lsmIterator_->next())
        {
            pageid_t *pid_tmp;

            pageid_t **hack = &pid_tmp;
            size_t ret = lsmIterator_->value((byte**)hack);
            assert(ret == sizeof(pageid_t));
            curr_pageid = *pid_tmp;
            curr_page = new DataPage(-1, ro_alloc_, curr_pageid);
            DEBUG("opening datapage iterator %lld at beginning\n.", curr_pageid);
            dp_itr = new DPITR_T(curr_page->begin());


            readTuple = dp_itr->getnext();
            assert(readTuple);
        }
      // else readTuple is null.  We're done.
    }

    if(readTuple && mgr_) {
      // c1_c2_progress_delta() is c1's out progress - c2's in progress.  We want to stop processing c2 if we are too far ahead (ie; c2 >> c1; delta << 0).
      while(mgr_->c1_c2_progress_delta() < -target_progress_delta_ && ((!flushing_) || (! *flushing_))) {  // TODO: how to pick this threshold?
        DEBUG("Input is too far behind.  Delta is %f\n", mgr_->c1_c2_progress_delta());
        struct timespec ts;
        mergeManager::double_to_ts(&ts, 0.01);
        nanosleep(&ts, 0);
        mgr_->update_progress(mgr_->get_merge_stats(1), 0);
      }
    }

    return readTuple;
}