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foundationdb/fdbclient/VersionedMap.h

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/*
* VersionedMap.h
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
*
* 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.
*/
#ifndef FDBCLIENT_VERSIONEDMAP_H
#define FDBCLIENT_VERSIONEDMAP_H
#pragma once
#include "flow/flow.h"
#include "flow/IndexedSet.h"
#include "FDBTypes.h"
#include "flow/IRandom.h"
#include "VersionedMap.actor.h"
// PTree is a persistent balanced binary tree implementation. It is based on a treap as a way to guarantee O(1) space for node insertion (rotating is asymptotically cheap),
// but the constant factors are very large.
//
// Each node has three pointers - the first two are its left and right children, respectively, and the third can be set to point to a newer version of the node.
// This third pointer allows us to maintain persistence without full path copying, and is employed to achieve O(1) space node insertion.
//
// PTree also supports efficient finger searches.
namespace PTreeImpl {
#pragma warning(disable: 4800)
template<class T>
struct PTree : public ReferenceCounted<PTree<T>>, FastAllocated<PTree<T>>, NonCopyable {
uint32_t priority;
Reference<PTree> pointer[3];
Version lastUpdateVersion;
bool updated;
bool replacedPointer;
T data;
Reference<PTree> child(bool which, Version at) const {
if (updated && lastUpdateVersion<=at && which == replacedPointer)
return pointer[2];
else
return pointer[which];
}
Reference<PTree> left(Version at) const { return child(false, at); }
Reference<PTree> right(Version at) const { return child(true, at); }
PTree(const T& data, Version ver) : data(data), lastUpdateVersion(ver), updated(false) {
priority = g_random->randomUInt32();
}
PTree( uint32_t pri, T const& data, Reference<PTree> const& left, Reference<PTree> const& right, Version ver ) : priority(pri), data(data), lastUpdateVersion(ver), updated(false) {
pointer[0] = left; pointer[1] = right;
}
private:
PTree(PTree const&);
};
template<class T>
static Reference<PTree<T>> update( Reference<PTree<T>> const& node, bool which, Reference<PTree<T>> const& ptr, Version at ) {
if (ptr.getPtr() == node->child(which, at).getPtr()/* && node->replacedVersion <= at*/) {
return node;
}
if (node->lastUpdateVersion == at) {
//&& (!node->updated || node->replacedPointer==which)) {
if (node->updated && node->replacedPointer != which) {
// We are going to have to copy this node, but its aux pointer will never be used again
// and should drop its reference count
Reference<PTree<T>> r;
if (which)
r = Reference<PTree<T>>( new PTree<T>( node->priority, node->data, node->child(0, at), ptr, at ) );
else
r = Reference<PTree<T>>( new PTree<T>( node->priority, node->data, ptr, node->child(1, at), at ) );
node->pointer[2].clear();
return r;
} else {
if (node->updated)
node->pointer[2] = ptr;
else
node->pointer[which] = ptr;
return node;
}
}
if ( node->updated ) {
if (which)
return Reference<PTree<T>>( new PTree<T>( node->priority, node->data, node->child(0, at), ptr, at ) );
else
return Reference<PTree<T>>( new PTree<T>( node->priority, node->data, ptr, node->child(1, at), at ) );
} else {
node->lastUpdateVersion = at;
node->replacedPointer = which;
node->pointer[2] = ptr;
node->updated = true;
return node;
}
}
template<class T, class X>
bool contains(const Reference<PTree<T>>& p, Version at, const X& x) {
if (!p) return false;
bool less = x < p->data;
if (!less && !(p->data<x)) return true; // x == p->data
return contains(p->child(!less, at), at, x);
}
template<class T, class X>
void lower_bound(const Reference<PTree<T>>& p, Version at, const X& x, std::vector<const PTree<T>*>& f){
if (!p) {
while (f.size() && !(x < f.back()->data))
f.pop_back();
return;
}
f.push_back(p.getPtr());
bool less = x < p->data;
if (!less && !(p->data<x)) return; // x == p->data
lower_bound(p->child(!less, at), at, x, f);
}
template<class T, class X>
void upper_bound(const Reference<PTree<T>>& p, Version at, const X& x, std::vector<const PTree<T>*>& f){
if (!p) {
while (f.size() && !(x < f.back()->data))
f.pop_back();
return;
}
f.push_back(p.getPtr());
upper_bound(p->child(!(x < p->data), at), at, x, f);
}
template<class T, bool forward>
void move(Version at, std::vector<const PTree<T>*>& f){
ASSERT(f.size());
const PTree<T> *n;
n = f.back();
if (n->child(forward, at)){
n = n->child(forward, at).getPtr();
do {
f.push_back(n);
n = n->child(!forward, at).getPtr();
} while (n);
} else {
do {
n = f.back();
f.pop_back();
} while (f.size() && f.back()->child(forward, at).getPtr() == n);
}
}
template<class T, bool forward>
int halfMove(Version at, std::vector<const PTree<T>*>& f) {
// Post: f[:return_value] is the finger that would have been returned by move<forward>(at,f), and f[:original_length_of_f] is unmodified
ASSERT(f.size());
const PTree<T> *n;
n = f.back();
if (n->child(forward, at)){
n = n->child(forward, at).getPtr();
do {
f.push_back(n);
n = n->child(!forward, at).getPtr();
} while (n);
return f.size();
} else {
int s = f.size();
do {
n = f[s-1];
--s;
} while (s && f[s-1]->child(forward, at).getPtr() == n);
return s;
}
}
template<class T>
void next(Version at, std::vector<const PTree<T>*>& f){
move<T,true>(at, f);
}
template<class T>
void previous(Version at, std::vector<const PTree<T>*>& f){
move<T,false>(at, f);
}
template<class T>
int halfNext(Version at, std::vector<const PTree<T>*>& f){
return halfMove<T,true>(at, f);
}
template<class T>
int halfPrevious(Version at, std::vector<const PTree<T>*>& f){
return halfMove<T,false>(at, f);
}
template<class T>
T get(std::vector<const PTree<T>*>& f){
ASSERT(f.size());
return f.back()->data;
}
// Modifies p to point to a PTree with x inserted
template<class T>
void insert(Reference<PTree<T>>& p, Version at, const T& x) {
if (!p){
p = Reference<PTree<T>>(new PTree<T>(x, at));
} else {
bool direction = !(x < p->data);
Reference<PTree<T>> child = p->child(direction, at);
insert(child, at, x);
p = update(p, direction, child, at);
if (p->child(direction, at)->priority > p->priority)
rotate(p, at, !direction);
}
}
template<class T>
Reference<PTree<T>> firstNode(const Reference<PTree<T>>& p, Version at) {
if (!p) ASSERT(false);
if (!p->left(at)) return p;
return firstNode(p->left(at), at);
}
template<class T>
Reference<PTree<T>> lastNode(const Reference<PTree<T>>& p, Version at) {
if (!p) ASSERT(false);
if (!p->right(at)) return p;
return lastNode(p->right(at), at);
}
template<class T, bool last>
void firstOrLastFinger(const Reference<PTree<T>>& p, Version at, std::vector<const PTree<T>*>& f) {
if (!p) return;
f.push_back(p.getPtr());
firstOrLastFinger<T, last>(p->child(last, at), at, f);
}
template<class T>
void first(const Reference<PTree<T>>& p, Version at, std::vector<const PTree<T>*>& f) {
return firstOrLastFinger<T, false>(p, at, f);
}
template<class T>
void last(const Reference<PTree<T>>& p, Version at, std::vector<const PTree<T>*>& f) {
return firstOrLastFinger<T, true>(p, at, f);
}
// modifies p to point to a PTree with the root of p removed
template<class T>
void removeRoot(Reference<PTree<T>>& p, Version at) {
if (!p->right(at))
p = p->left(at);
else if (!p->left(at))
p = p->right(at);
else {
bool direction = p->right(at)->priority < p->left(at)->priority;
rotate(p,at,direction);
Reference<PTree<T>> child = p->child(direction, at);
removeRoot(child, at);
p = update(p, direction, child, at);
}
}
// changes p to point to a PTree with x removed
template<class T, class X>
void remove(Reference<PTree<T>>& p, Version at, const X& x) {
if (!p) ASSERT(false); // attempt to remove item not present in PTree
if (x < p->data) {
Reference<PTree<T>> child = p->child(0, at);
remove(child, at, x);
p = update(p, 0, child, at);
} else if (p->data < x) {
Reference<PTree<T>> child = p->child(1, at);
remove(child, at, x);
p = update(p, 1, child, at);
} else
removeRoot(p, at);
}
template<class T, class X>
void remove(Reference<PTree<T>>& p, Version at, const X& begin, const X& end) {
if (!p) return;
int beginDir, endDir;
if (begin < p->data) beginDir = -1;
else if (p->data < begin) beginDir = +1;
else beginDir = 0;
if (!(p->data < end)) endDir = -1;
else endDir = +1;
if (beginDir == endDir) {
Reference<PTree<T>> child = p->child(beginDir==+1, at);
remove( child, at, begin, end );
p = update(p, beginDir==+1, child, at);
} else {
if (beginDir==-1) {
Reference<PTree<T>> left = p->child(0, at);
removeBeyond(left, at, begin, 1);
p = update(p, 0, left, at);
}
if (endDir==+1) {
Reference<PTree<T>> right = p->child(1, at);
removeBeyond(right, at, end, 0);
p = update(p, 1, right, at);
}
if (beginDir < endDir)
removeRoot(p, at);
}
}
template <class T, class X>
void removeBeyond(Reference<PTree<T>>& p, Version at, const X& pivot, bool dir) {
if (!p) return;
if ( (p->data < pivot)^dir ) {
p = p->child(!dir, at);
removeBeyond(p, at, pivot, dir );
} else {
Reference<PTree<T>> child = p->child(dir, at);
removeBeyond(child, at, pivot, dir);
p = update(p, dir, child, at);
}
}
/*template<class T, class X>
void remove(Reference<PTree<T>>& p, Version at, const X& begin, const X& end) {
Reference<PTree<T>> left, center, right;
split(p, begin, left, center, at);
split(center, end, center, right, at);
p = append(left, right, at);
}*/
// inputs a PTree with the root node potentially violating the heap property
// modifies p to point to a valid PTree
template<class T>
void demoteRoot(Reference<PTree<T>>& p, Version at){
if (!p) ASSERT(false);
uint32_t priority[2];
for (int i=0;i<2;i++)
if (p->child(i, at)) priority[i] = p->child(i, at)->priority;
else priority[i] = 0;
bool higherDirection = priority[1] > priority[0];
if (priority[higherDirection] < p->priority) return;
// else, child(higherDirection) is a greater priority than us and the other child...
rotate(p, at, !higherDirection);
Reference<PTree<T>> child = p->child(!higherDirection, at);
demoteRoot(child, at);
p = update(p, !higherDirection, child, at);
}
template<class T>
Reference<PTree<T>> append(const Reference<PTree<T>>& left, const Reference<PTree<T>>& right, Version at) {
if (!left) return right;
if (!right) return left;
Reference<PTree<T>> r = Reference<PTree<T>>(new PTree<T>(lastNode(left, at)->data, at));
ASSERT( r->data < firstNode(right, at)->data);
Reference<PTree<T>> a = left;
remove(a, at, r->data);
r->pointer[0] = a;
r->pointer[1] = right;
demoteRoot(r, at);
return r;
}
template<class T, class X>
void split(Reference<PTree<T>> p, const X& x, Reference<PTree<T>>& left, Reference<PTree<T>>& right, Version at) {
if (!p){
left = Reference<PTree<T>>();
right = Reference<PTree<T>>();
return;
}
if (p->data < x){
left = p;
Reference<PTree<T>> lr = left->right(at);
split(lr, x, lr, right, at);
left = update(left, 1, lr, at);
} else {
right = p;
Reference<PTree<T>> rl = right->left(at);
split(rl, x, left, rl, at);
right = update(right, 0, rl, at);
}
}
template<class T>
void rotate(Reference<PTree<T>>& p, Version at, bool right){
auto r = p->child(!right, at);
auto n1 = r->child(!right, at);
auto n2 = r->child(right, at);
auto n3 = p->child(right, at);
auto newC = update( p, !right, n2, at );
newC = update( newC, right, n3, at );
p = update( r, !right, n1, at );
p = update( p, right, newC, at );
}
template <class T>
void printTree(const Reference<PTree<T>>& p, Version at, int depth = 0) {
if (p->left(at)) printTree(p->left(at), at, depth+1);
for (int i=0;i<depth;i++)
printf(" ");
printf(":%s\n", describe(p->data).c_str());
if (p->right(at)) printTree(p->right(at), at, depth+1);
}
template <class T>
void printTreeDetails(const Reference<PTree<T>>& p, int depth = 0) {
printf("Node %p (depth %d): %s\n", p.getPtr(), depth, describe(p->data).c_str());
printf(" Left: %p\n", p->pointer[0].getPtr());
printf(" Right: %p\n", p->pointer[1].getPtr());
if (p->pointer[2])
printf(" Version %lld %s: %p\n", p->lastUpdateVersion, p->replacedPointer ? "Right" : "Left", p->pointer[2].getPtr());
for(int i=0; i<3; i++)
if (p->pointer[i]) printTreeDetails(p->pointer[i], depth+1);
}
/*static int depth(const Reference<PTree<int>>& p, Version at) {
if (!p) return 0;
int d1 = depth(p->left(at), at) + 1;
int d2 = depth(p->right(at), at) + 1;
return d1 > d2 ? d1 : d2;
}*/
template <class T>
void validate(const Reference<PTree<T>>& p, Version at, T* min, T* max, int& count, int& height, int depth=0) {
if (!p) { height=0; return; }
ASSERT( (!min || *min <= p->data) && (!max || p->data <= *max) );
for (int i=0;i<2;i++){
if (p->child(i, at))
ASSERT(p->child(i, at)->priority <= p->priority);
}
++count;
int h1, h2;
validate(p->left(at), at, min, &p->data, count, h1, depth+1);
validate(p->right(at), at, &p->data, max, count, h2, depth+1);
height = std::max(h1, h2) + 1;
}
template<class T>
void check(const Reference<PTree<T>>& p){
int count=0, height;
validate(p, (T*)0, (T*)0, count, height);
if (count && height > 4.3 * log(double(count))){
//printf("height %d; count %d\n", height, count);
ASSERT(false);
}
}
}
// VersionedMap provides an interface to a partially persistent tree, allowing you to read the values at a particular version,
// create new versions, modify the current version of the tree, and forget versions prior to a specific version.
template <class K, class T>
class VersionedMap : NonCopyable {
//private:
public:
typedef PTreeImpl::PTree<MapPair<K,std::pair<T,Version>>> PTreeT;
typedef Reference< PTreeT > Tree;
Version oldestVersion, latestVersion;
std::map<Version, Tree> roots;
Tree *latestRoot;
Tree const& getRoot( Version v ) const {
auto r = roots.upper_bound(v);
--r;
return r->second;
}
static const int overheadPerItem = 128*4;
struct iterator;
VersionedMap() : oldestVersion(0), latestVersion(0) {
latestRoot = &roots[0];
}
VersionedMap( VersionedMap&& v ) noexcept(true) : oldestVersion(v.oldestVersion), latestVersion(v.latestVersion), roots(std::move(v.roots)) {
latestRoot = &roots[latestVersion];
}
void operator = (VersionedMap && v) noexcept(true) {
oldestVersion = v.oldestVersion;
latestVersion = v.latestVersion;
roots = std::move(v.roots);
latestRoot = &roots[latestVersion];
}
Version getLatestVersion() const { return latestVersion; }
Version getOldestVersion() const { return oldestVersion; }
Version getNextOldestVersion() const { return roots.upper_bound(oldestVersion)->first; }
void forgetVersionsBefore(Version newOldestVersion) {
ASSERT( newOldestVersion <= latestVersion );
roots[newOldestVersion] = getRoot(newOldestVersion);
roots.erase(roots.begin(), roots.lower_bound(newOldestVersion));
oldestVersion = newOldestVersion;
}
Future<Void> forgetVersionsBeforeAsync( Version newOldestVersion, int taskID = 7000 ) {
ASSERT( newOldestVersion <= latestVersion );
roots[newOldestVersion] = getRoot(newOldestVersion);
vector<Tree> toFree;
auto newBegin = roots.lower_bound(newOldestVersion);
for(auto root = roots.begin(); root != roots.end() && root != newBegin; ++root) {
if(root->second && root->second->isSoleOwner())
toFree.push_back(root->second);
}
roots.erase(roots.begin(), newBegin);
oldestVersion = newOldestVersion;
return deferredCleanupActor(toFree, taskID);
}
public:
void createNewVersion(Version version) { // following sets and erases are into the given version, which may now be passed to at(). Must be called in monotonically increasing order.
if (version > latestVersion) {
latestVersion = version;
Tree r = getRoot(version);
latestRoot = &roots[version];
*latestRoot = r;
} else ASSERT( version == latestVersion );
}
// insert() and erase() invalidate atLatest() and all iterators into it
void insert(const K& k, const T& t) {
insert( k, t, latestVersion );
}
void insert(const K& k, const T& t, Version insertAt) {
if (PTreeImpl::contains( *latestRoot, latestVersion, k )) PTreeImpl::remove( *latestRoot, latestVersion, k ); // FIXME: Make PTreeImpl::insert do this automatically (see also WriteMap.h FIXME)
PTreeImpl::insert( *latestRoot, latestVersion, MapPair<K,std::pair<T,Version>>(k,std::make_pair(t,insertAt)) );
}
void erase(const K& begin, const K& end) {
PTreeImpl::remove( *latestRoot, latestVersion, begin, end );
}
void erase(const K& key ) { // key must be present
PTreeImpl::remove( *latestRoot, latestVersion, key );
}
void erase(iterator const& item) { // iterator must be in latest version!
// SOMEDAY: Optimize to use item.finger and avoid repeated search
K key = item.key();
erase(key);
}
// for(auto i = vm.at(version).lower_bound(range.begin); i < range.end; ++i)
struct iterator{
explicit iterator(Tree const& root, Version at) : root(root), at(at) {}
K const& key() const { return finger.back()->data.key; }
Version insertVersion() const { return finger.back()->data.value.second; } // Returns the version at which the current item was inserted
operator bool() const { return finger.size()!=0; }
bool operator < (const K& key) const { return this->key() < key; }
T const& operator*() { return finger.back()->data.value.first; }
T const* operator->() { return &finger.back()->data.value.first; }
void operator++() { if (finger.size()) PTreeImpl::next( at, finger ); else PTreeImpl::first(root, at, finger); }
void operator--() { if (finger.size()) PTreeImpl::previous( at, finger ); else PTreeImpl::last(root, at, finger); }
bool operator == ( const iterator& r ) const { if (finger.size() && r.finger.size()) return finger.back() == r.finger.back(); else return finger.size()==r.finger.size(); }
bool operator != ( const iterator& r ) const { if (finger.size() && r.finger.size()) return finger.back() != r.finger.back(); else return finger.size()!=r.finger.size(); }
private:
friend class VersionedMap<K,T>;
Tree root;
Version at;
vector< PTreeT const* > finger;
};
class ViewAtVersion {
public:
ViewAtVersion(Tree const& root, Version at) : root(root), at(at) {}
iterator begin() const { iterator i(root,at); PTreeImpl::first( root, at, i.finger ); return i; }
iterator end() const { return iterator(root,at); }
// Returns x such that key==*x, or end()
template <class X>
iterator find(const X &key) const {
iterator i(root,at);
PTreeImpl::lower_bound( root, at, key, i.finger );
if (i && i.key() == key)
return i;
else
return end();
}
// Returns the smallest x such that *x>=key, or end()
template <class X>
iterator lower_bound(const X &key) const {
iterator i(root,at);
PTreeImpl::lower_bound( root, at, key, i.finger );
return i;
}
// Returns the smallest x such that *x>key, or end()
template <class X>
iterator upper_bound(const X &key) const {
iterator i(root,at);
PTreeImpl::upper_bound( root, at, key, i.finger );
return i;
}
// Returns the largest x such that *x<=key, or end()
template <class X>
iterator lastLessOrEqual( const X &key ) const {
iterator i(root,at);
PTreeImpl::upper_bound( root, at, key, i.finger );
--i;
return i;
}
// Returns the largest x such that *x<key, or end()
template <class X>
iterator lastLess( const X &key ) const {
iterator i(root,at);
PTreeImpl::lower_bound( root, at, key, i.finger );
--i;
return i;
}
void validate() {
int count=0, height=0;
PTreeImpl::validate<MapPair<K,std::pair<T,Version>>>( root, at, NULL, NULL, count, height );
if ( height > 100 )
TraceEvent(SevWarnAlways, "DiabolicalPTreeSize").detail("size", count).detail("height", height);
}
private:
Tree root;
Version at;
};
ViewAtVersion at( Version v ) const { return ViewAtVersion(getRoot(v), v); }
ViewAtVersion atLatest() const { return ViewAtVersion(*latestRoot, latestVersion); }
// TODO: getHistory?
};
#endif
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