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vesoft-inc · Mar 20, 2023 · 5875f89 · 5875f89
1 parent d4d552b
commit 5875f89
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Showing 3 changed files with 27 additions and 4 deletions.
diff --git a/src/graph/executor/algo/AllPathsExecutor.cpp b/src/graph/executor/algo/AllPathsExecutor.cpp
@@ -7,8 +7,11 @@
 #include "graph/planner/plan/Algo.h"
 #include "graph/service/GraphFlags.h"
 
-DEFINE_uint32(path_threshold_size, 100, "");
-DEFINE_uint32(path_threshold_ratio, 2, "");
+DEFINE_uint32(
+    path_threshold_size,
+    100,
+    "the number of vids to expand, when this threshold is exceeded, use heuristic expansion");
+DEFINE_uint32(path_threshold_ratio, 2, "threshold for heuristics expansion");
 DEFINE_uint32(path_batch_size, 5000, "number of paths constructed by each thread");
 
 namespace nebula {
@@ -402,7 +405,7 @@ folly::Future<std::vector<Row>> AllPathsExecutor::doBuildPath(
     }
   }
   return folly::collect(futures).via(runner()).thenValue(
-      [this, pathPtr = std::move(currentPathPtr), step](std::vector<std::vector<Row>>&& paths) {
+      [pathPtr = std::move(currentPathPtr)](std::vector<std::vector<Row>>&& paths) {
         memory::MemoryCheckGuard guard;
         std::vector<Row> result = std::move(*pathPtr);
         for (auto& path : paths) {

diff --git a/src/graph/executor/algo/AllPathsExecutor.h b/src/graph/executor/algo/AllPathsExecutor.h
@@ -7,6 +7,26 @@
 
 #include "graph/executor/PathBaseExecutor.h"
 
+// Using the two-way BFS algorithm, a heuristic algorithm is used in the expansion process
+// when the number of vid to be expanded on the left and right
+// exceeds the threshold(FLAGS_path_threshold_size)
+
+// if size(leftVids) / size(rightVids) >= FLAGS_path_threshold_ratio(default 2)
+//    expandFromRight
+// else if size(rightVids) / size(leftVids) >= FLAGS_path_threshold_ratio(default 2)
+//    expandFromLeft
+// else
+//    expandFromLeft
+//    expandFromRight
+// this way can avoid uneven calculation distribution due to data skew
+// finally the path is constructed using an asynchronous process in the adjacency list
+
+// adjList is an adjacency list structure
+// which saves the vids and all adjacent edges that expand one step
+// when expanding, if the vid has already been visited, do not visit again
+// leftAdjList_ save result of forward expansion
+// rightAdjList_ save result of backward expansion
+
 namespace nebula {
 namespace graph {
 class AllPaths;

diff --git a/src/graph/executor/query/TraverseExecutor.h b/src/graph/executor/query/TraverseExecutor.h
@@ -5,7 +5,7 @@
 #ifndef EXECUTOR_QUERY_TRAVERSEEXECUTOR_H_
 #define EXECUTOR_QUERY_TRAVERSEEXECUTOR_H_
 
-// #include <robin_hood.h>
+#include <robin_hood.h>
 
 #include "graph/executor/StorageAccessExecutor.h"
 #include "graph/planner/plan/Query.h"