optimizer path (#4162)

* optimizer multi-shortest path

* new algorithm

* fix error

Author: nevermore3

src/graph/executor/algo/BFSShortestPathExecutor.cpp

@@ -135,13 +135,12 @@ folly::Future<Status> BFSShortestPathExecutor::conjunctPath() {
   std::vector<folly::Future<DataSet>> futures;
   for (auto& vid : meetVids) {
     batchVids.push_back(vid);
-    if (i == totalSize - 1 || batchVids.size() == batchSize) {
+    if (++i == totalSize || batchVids.size() == batchSize) {
       auto future = folly::via(runner(), [this, vids = std::move(batchVids), oddStep]() {
         return doConjunct(vids, oddStep);
       });
       futures.emplace_back(std::move(future));
     }
-    i++;
   }
 
   return folly::collect(futures).via(runner()).thenValue([this](auto&& resps) {

src/graph/executor/algo/MultiShortestPathExecutor.cpp

@@ -39,10 +39,19 @@ folly::Future<Status> MultiShortestPathExecutor::execute() {
       })
       .thenValue([this](auto&& resp) {
         UNUSED(resp);
-        preLeftPaths_.swap(leftPaths_);
-        preRightPaths_.swap(rightPaths_);
+        preRightPaths_ = rightPaths_;
+        // update history
+        for (auto& iter : leftPaths_) {
+          historyLeftPaths_[iter.first].insert(std::make_move_iterator(iter.second.begin()),
+                                               std::make_move_iterator(iter.second.end()));
+        }
+        for (auto& iter : rightPaths_) {
+          historyRightPaths_[iter.first].insert(std::make_move_iterator(iter.second.begin()),
+                                                std::make_move_iterator(iter.second.end()));
+        }
         leftPaths_.clear();
         rightPaths_.clear();
+
         step_++;
         DataSet ds;
         ds.colNames = pathNode_->colNames();
@@ -58,24 +67,40 @@ void MultiShortestPathExecutor::init() {
   for (; rIter->valid(); rIter->next()) {
     auto& vid = rIter->getColumn(0);
     if (rightVids.emplace(vid).second) {
-      preRightPaths_[vid].push_back({Path(Vertex(vid, {}), {})});
+      std::vector<Path> tmp({Path(Vertex(vid, {}), {})});
+      historyRightPaths_[vid].emplace(vid, tmp);
+      preRightPaths_[vid].emplace(vid, std::move(tmp));
     }
   }
 
   std::set<Value> leftVids;
   for (; lIter->valid(); lIter->next()) {
     auto& vid = lIter->getColumn(0);
+    std::vector<Path> tmp({Path(Vertex(vid, {}), {})});
+    historyLeftPaths_[vid].emplace(vid, std::move(tmp));
     leftVids.emplace(vid);
   }
   for (const auto& leftVid : leftVids) {
     for (const auto& rightVid : rightVids) {
       if (leftVid != rightVid) {
-        terminationMap_.insert({leftVid, {rightVid, true}});
+        terminationMap_.emplace(leftVid, std::make_pair(rightVid, true));
       }
     }
   }
 }
 
+std::vector<Path> MultiShortestPathExecutor::createPaths(const std::vector<Path>& paths,
+                                                         const Edge& edge) {
+  std::vector<Path> newPaths;
+  newPaths.reserve(paths.size());
+  for (const auto& p : paths) {
+    Path path = p;
+    path.steps.emplace_back(Step(Vertex(edge.dst, {}), edge.type, edge.name, edge.ranking, {}));
+    newPaths.emplace_back(std::move(path));
+  }
+  return newPaths;
+}
+
 Status MultiShortestPathExecutor::buildPath(bool reverse) {
   auto iter = reverse ? ectx_->getResult(pathNode_->rightInputVar()).iter()
                       : ectx_->getResult(pathNode_->leftInputVar()).iter();
@@ -96,10 +121,23 @@ Status MultiShortestPathExecutor::buildPath(bool reverse) {
       Path path;
       path.src = Vertex(src, {});
       path.steps.emplace_back(Step(Vertex(dst, {}), edge.type, edge.name, edge.ranking, {}));
-      currentPaths[dst].emplace_back(std::move(path));
+      auto foundDst = currentPaths.find(dst);
+      if (foundDst != currentPaths.end()) {
+        auto foundSrc = foundDst->second.find(src);
+        if (foundSrc != foundDst->second.end()) {
+          // same <src, dst>, different edge type or rank
+          foundSrc->second.emplace_back(std::move(path));
+        } else {
+          std::vector<Path> tmp({std::move(path)});
+          foundDst->second.emplace(src, std::move(tmp));
+        }
+      } else {
+        std::vector<Path> tmp({std::move(path)});
+        currentPaths[dst].emplace(src, std::move(tmp));
+      }
     }
   } else {
-    auto& historyPaths = reverse ? preRightPaths_ : preLeftPaths_;
+    auto& historyPaths = reverse ? historyRightPaths_ : historyLeftPaths_;
     for (; iter->valid(); iter->next()) {
       auto edgeVal = iter->getEdge();
       if (UNLIKELY(!edgeVal.isEdge())) {
@@ -108,50 +146,93 @@ Status MultiShortestPathExecutor::buildPath(bool reverse) {
       auto& edge = edgeVal.getEdge();
       auto& src = edge.src;
       auto& dst = edge.dst;
-      for (const auto& histPath : historyPaths[src]) {
-        Path path = histPath;
-        path.steps.emplace_back(Step(Vertex(dst, {}), edge.type, edge.name, edge.ranking, {}));
-        if (path.hasDuplicateVertices()) {
-          continue;
+      auto& prePaths = historyPaths[src];
+
+      auto foundHistDst = historyPaths.find(dst);
+      if (foundHistDst == historyPaths.end()) {
+        // dst not in history
+        auto foundDst = currentPaths.find(dst);
+        if (foundDst == currentPaths.end()) {
+          // dst not in current, new edge
+          for (const auto& prePath : prePaths) {
+            currentPaths[dst].emplace(prePath.first, createPaths(prePath.second, edge));
+          }
+        } else {
+          // dst in current
+          for (const auto& prePath : prePaths) {
+            auto newPaths = createPaths(prePath.second, edge);
+            auto foundSrc = foundDst->second.find(prePath.first);
+            if (foundSrc == foundDst->second.end()) {
+              foundDst->second.emplace(prePath.first, std::move(newPaths));
+            } else {
+              foundSrc->second.insert(foundSrc->second.begin(),
+                                      std::make_move_iterator(newPaths.begin()),
+                                      std::make_move_iterator(newPaths.end()));
+            }
+          }
+        }
+      } else {
+        // dst in history
+        auto& historyDstPaths = foundHistDst->second;
+        for (const auto& prePath : prePaths) {
+          if (historyDstPaths.find(prePath.first) != historyDstPaths.end()) {
+            // loop: a->b->c->a or a->b->c->b,
+            // filter out path that with duplicate vertex or have already been found before
+            continue;
+          }
+          auto foundDst = currentPaths.find(dst);
+          if (foundDst == currentPaths.end()) {
+            currentPaths[dst].emplace(prePath.first, createPaths(prePath.second, edge));
+          } else {
+            auto newPaths = createPaths(prePath.second, edge);
+            auto foundSrc = foundDst->second.find(prePath.first);
+            if (foundSrc == foundDst->second.end()) {
+              foundDst->second.emplace(prePath.first, std::move(newPaths));
+            } else {
+              foundSrc->second.insert(foundSrc->second.begin(),
+                                      std::make_move_iterator(newPaths.begin()),
+                                      std::make_move_iterator(newPaths.end()));
+            }
+          }
         }
-        currentPaths[dst].emplace_back(std::move(path));
       }
     }
   }
+
   // set nextVid
   const auto& nextVidVar = reverse ? pathNode_->rightVidVar() : pathNode_->leftVidVar();
   setNextStepVid(currentPaths, nextVidVar);
   return Status::OK();
 }
 
-DataSet MultiShortestPathExecutor::doConjunct(Interims::iterator startIter,
-                                              Interims::iterator endIter,
-                                              bool oddStep) {
-  auto& rightPaths = oddStep ? preRightPaths_ : rightPaths_;
-  DataSet ds;
-  for (; startIter != endIter; ++startIter) {
-    auto found = rightPaths.find(startIter->first);
-    if (found == rightPaths.end()) {
-      continue;
-    }
-    for (const auto& lPath : startIter->second) {
-      const auto& srcVid = lPath.src.vid;
-      auto range = terminationMap_.equal_range(srcVid);
-      for (const auto& rPath : found->second) {
-        const auto& dstVid = rPath.src.vid;
-        for (auto iter = range.first; iter != range.second; ++iter) {
-          if (iter->second.first == dstVid) {
-            auto forwardPath = lPath;
-            auto backwardPath = rPath;
+DataSet MultiShortestPathExecutor::doConjunct(
+    const std::vector<std::pair<Interims::iterator, Interims::iterator>>& iters) {
+  auto buildPaths =
+      [](const std::vector<Path>& leftPaths, const std::vector<Path>& rightPaths, DataSet& ds) {
+        for (const auto& leftPath : leftPaths) {
+          for (const auto& rightPath : rightPaths) {
+            auto forwardPath = leftPath;
+            auto backwardPath = rightPath;
             backwardPath.reverse();
             forwardPath.append(std::move(backwardPath));
-            if (forwardPath.hasDuplicateVertices()) {
-              continue;
-            }
             Row row;
             row.values.emplace_back(std::move(forwardPath));
             ds.rows.emplace_back(std::move(row));
-            iter->second.second = false;
+          }
+        }
+      };
+
+  DataSet ds;
+  for (const auto& iter : iters) {
+    const auto& leftPaths = iter.first->second;
+    const auto& rightPaths = iter.second->second;
+    for (const auto& leftPath : leftPaths) {
+      auto range = terminationMap_.equal_range(leftPath.first);
+      for (const auto& rightPath : rightPaths) {
+        for (auto found = range.first; found != range.second; ++found) {
+          if (found->second.first == rightPath.first) {
+            buildPaths(leftPath.second, rightPath.second, ds);
+            found->second.second = false;
           }
         }
       }
@@ -161,28 +242,51 @@ DataSet MultiShortestPathExecutor::doConjunct(Interims::iterator startIter,
 }
 
 folly::Future<bool> MultiShortestPathExecutor::conjunctPath(bool oddStep) {
-  size_t batchSize = leftPaths_.size() / static_cast<size_t>(FLAGS_num_operator_threads);
+  auto& rightPaths = oddStep ? preRightPaths_ : rightPaths_;
+  size_t leftPathSize = leftPaths_.size();
+  size_t rightPathSize = rightPaths.size();
   std::vector<folly::Future<DataSet>> futures;
-  size_t i = 0;
+  std::vector<std::pair<Interims::iterator, Interims::iterator>> pathIters;
 
-  auto startIter = leftPaths_.begin();
-  for (auto leftIter = leftPaths_.begin(); leftIter != leftPaths_.end(); ++leftIter) {
-    if (i++ == batchSize) {
-      auto endIter = leftIter;
-      endIter++;
-      auto future = folly::via(runner(), [this, startIter, endIter, oddStep]() {
-        return doConjunct(startIter, endIter, oddStep);
-      });
-      futures.emplace_back(std::move(future));
-      i = 0;
-      startIter = endIter;
+  size_t i = 0;
+  if (leftPathSize > rightPathSize) {
+    size_t batchSize = leftPathSize / static_cast<size_t>(FLAGS_num_operator_threads);
+    pathIters.reserve(batchSize);
+    for (auto leftIter = leftPaths_.begin(); leftIter != leftPaths_.end(); ++leftIter) {
+      auto rightIter = rightPaths.find(leftIter->first);
+      if (rightIter == rightPaths.end()) {
+        continue;
+      }
+      pathIters.emplace_back(leftIter, rightIter);
+      if (++i == batchSize) {
+        auto future = folly::via(
+            runner(), [this, iters = std::move(pathIters)]() { return doConjunct(iters); });
+        futures.emplace_back(std::move(future));
+        pathIters.reserve(batchSize);
+        i = 0;
+      }
+    }
+  } else {
+    size_t batchSize = rightPathSize / static_cast<size_t>(FLAGS_num_operator_threads);
+    pathIters.reserve(batchSize);
+    for (auto rightIter = rightPaths.begin(); rightIter != rightPaths.end(); ++rightIter) {
+      auto leftIter = leftPaths_.find(rightIter->first);
+      if (leftIter == leftPaths_.end()) {
+        continue;
+      }
+      pathIters.emplace_back(leftIter, rightIter);
+      if (++i == batchSize) {
+        auto future = folly::via(
+            runner(), [this, iters = std::move(pathIters)]() { return doConjunct(iters); });
+        futures.emplace_back(std::move(future));
+        pathIters.reserve(batchSize);
+        i = 0;
+      }
     }
   }
   if (i != 0) {
-    auto endIter = leftPaths_.end();
-    auto future = folly::via(runner(), [this, startIter, endIter, oddStep]() {
-      return doConjunct(startIter, endIter, oddStep);
-    });
+    auto future =
+        folly::via(runner(), [this, iters = std::move(pathIters)]() { return doConjunct(iters); });
     futures.emplace_back(std::move(future));
   }
 

src/graph/executor/algo/MultiShortestPathExecutor.h

@@ -57,24 +57,27 @@ class MultiShortestPathExecutor final : public Executor {
   folly::Future<Status> execute() override;
 
  private:
-  // k: dst, v: paths to dst
-  using Interims = std::unordered_map<Value, std::vector<Path>>;
+  // key: dst, value: {key : src, value: paths}
+  using Interims = std::unordered_map<Value, std::unordered_map<Value, std::vector<Path>>>;
 
   void init();
+  std::vector<Path> createPaths(const std::vector<Path>& paths, const Edge& edge);
   Status buildPath(bool reverse);
   folly::Future<bool> conjunctPath(bool oddStep);
-  DataSet doConjunct(Interims::iterator startIter, Interims::iterator endIter, bool oddStep);
+  DataSet doConjunct(const std::vector<std::pair<Interims::iterator, Interims::iterator>>& iters);
   void setNextStepVid(const Interims& paths, const string& var);
 
  private:
   const MultiShortestPath* pathNode_{nullptr};
   size_t step_{1};
   std::string terminationVar_;
+  // {src, <dst, true>}
   std::unordered_multimap<Value, std::pair<Value, bool>> terminationMap_;
   Interims leftPaths_;
-  Interims preLeftPaths_;
-  Interims preRightPaths_;
   Interims rightPaths_;
+  Interims preRightPaths_;
+  Interims historyLeftPaths_;
+  Interims historyRightPaths_;
   DataSet currentDs_;
 };
 

src/graph/executor/algo/ProduceAllPathsExecutor.cpp

@@ -132,7 +132,7 @@ folly::Future<Status> ProduceAllPathsExecutor::conjunctPath() {
 
   auto startIter = leftPaths_.begin();
   for (auto leftIter = leftPaths_.begin(); leftIter != leftPaths_.end(); ++leftIter) {
-    if (i++ == batchSize) {
+    if (++i == batchSize) {
       auto endIter = leftIter;
       endIter++;
       auto oddStepFuture = folly::via(

src/graph/executor/test/FindPathTest.cpp

@@ -710,7 +710,7 @@ TEST_F(FindPathTest, multiSourceShortestPath) {
     {
       DataSet expectLeftVid;
       expectLeftVid.colNames = {nebula::kVid};
-      for (const auto& vid : {"a", "b", "c", "f", "g"}) {
+      for (const auto& vid : {"b", "f", "g"}) {
         Row row;
         row.values.emplace_back(vid);
         expectLeftVid.rows.emplace_back(std::move(row));

src/graph/service/GraphFlags.cpp

@@ -18,7 +18,7 @@ DEFINE_int32(num_netio_threads,
              "The number of networking threads, 0 for number of physical CPU cores");
 DEFINE_int32(num_accept_threads, 1, "Number of threads to accept incoming connections");
 DEFINE_int32(num_worker_threads, 0, "Number of threads to execute user queries");
-DEFINE_int32(num_operator_threads, 5, "Number of threads to execute a single operator");
+DEFINE_int32(num_operator_threads, 2, "Number of threads to execute a single operator");
 DEFINE_bool(reuse_port, true, "Whether to turn on the SO_REUSEPORT option");
 DEFINE_int32(listen_backlog, 1024, "Backlog of the listen socket");
 DEFINE_string(listen_netdev, "any", "The network device to listen on");