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kuzudb · May 14, 2023 · ae70e7f · ae70e7f
1 parent ba5aa84
commit ae70e7f
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Showing 2 changed files with 22 additions and 11 deletions.
diff --git a/src/include/processor/operator/recursive_extend/path_scanner.h b/src/include/processor/operator/recursive_extend/path_scanner.h
@@ -5,11 +5,15 @@
 namespace kuzu {
 namespace processor {
 
+// FixedSizePathScanner scans all path for a fixed length.
 struct FixedSizePathScanner {
     const BaseBFSMorsel& bfsMorsel;
+    // Number of extension performed during recursive join
     size_t depth;
-
+    // Current path. TODO(Xiyang): we can remove this and directly read from cursor and nbrs.
     std::vector<common::offset_t> path;
+
+    // States
     std::vector<size_t> cursorPerDepth;
     std::vector<std::vector<common::offset_t>*> nbrsPerDepth;
     common::offset_t currentDstOffset;
@@ -32,17 +36,10 @@ struct FixedSizePathScanner {
 private:
     bool dfs(size_t currentDepth);
 
-    void initDfs(common::offset_t offset, size_t currentDepth) {
-        path[currentDepth] = offset;
-        if (currentDepth == 0) {
-            return;
-        }
-        nbrsPerDepth[currentDepth - 1] = &bfsMorsel.frontiers[currentDepth]->bwdEdges.at(offset);
-        cursorPerDepth[currentDepth - 1] = 0;
-        initDfs(nbrsPerDepth[currentDepth - 1]->at(0), currentDepth - 1);
-    }
+    void initDfs(common::offset_t offset, size_t currentDepth);
 };
 
+// PathScanner scans path whose length falls into [lowerBound, upperBound].
 struct PathScanner {
     size_t lowerBound;
     size_t upperBound;

diff --git a/src/processor/operator/recursive_extend/path_scanner.cpp b/src/processor/operator/recursive_extend/path_scanner.cpp
@@ -4,12 +4,14 @@ namespace kuzu {
 namespace processor {
 
 bool FixedSizePathScanner::getNext() {
-    if (depth >= bfsMorsel.frontiers.size()) { // BFS terminate before current depth
+    if (depth >= bfsMorsel.frontiers.size()) {
+        // BFS terminate before current depth. No need to scan.
         return false;
     }
     auto frontier = bfsMorsel.frontiers[depth].get();
     auto& cursor = cursorPerDepth[depth];
     if (dfs(0)) {
+        // Find a path for currentDstOffset;
         return true;
     }
     while (cursor < frontier->nodeOffsets.size()) {
@@ -19,6 +21,8 @@ bool FixedSizePathScanner::getNext() {
             !bfsMorsel.targetDstNodeOffsets.contains(currentDstOffset)) {
             continue;
         }
+        // Init nbrs and first path. We guarantee (from BFS computation) to have at least one path
+        // that reaches currentDstOffset.
         initDfs(currentDstOffset, depth);
         return true;
     }
@@ -49,6 +53,16 @@ bool FixedSizePathScanner::dfs(size_t currentDepth) {
     }
 }
 
+void FixedSizePathScanner::initDfs(common::offset_t offset, size_t currentDepth) {
+    path[currentDepth] = offset;
+    if (currentDepth == 0) {
+        return;
+    }
+    nbrsPerDepth[currentDepth - 1] = &bfsMorsel.frontiers[currentDepth]->bwdEdges.at(offset);
+    cursorPerDepth[currentDepth - 1] = 0;
+    initDfs(nbrsPerDepth[currentDepth - 1]->at(0), currentDepth - 1);
+}
+
 bool PathScanner::getNext() {
     while (cursor < scanners.size()) {
         if (scanners[cursor]->getNext()) {