Skip next row vector free when clear row container (facebookincubator…

…#11101)

Summary: Pull Request resolved: facebookincubator#11101

Reviewed By: Yuhta

Differential Revision: D63442387

fbshipit-source-id: 9166e485ec1605913c3706256a9a9f532d914a45

velox/exec/RowContainer.cpp

@@ -336,7 +336,7 @@ char* RowContainer::initializeRow(char* row, bool reuse) {
 }
 
 void RowContainer::eraseRows(folly::Range<char**> rows) {
-  freeRowsExtraMemory(rows, false);
+  freeRowsExtraMemory(rows, /*freeNextRowVector=*/true);
   for (auto* row : rows) {
     VELOX_CHECK(!bits::isBitSet(row, freeFlagOffset_), "Double free of row");
     bits::setBit(row, freeFlagOffset_);
@@ -457,31 +457,11 @@ void RowContainer::freeAggregates(folly::Range<char**> rows) {
   }
 }
 
-void RowContainer::freeNextRowVectors(folly::Range<char**> rows, bool clear) {
+void RowContainer::freeNextRowVectors(folly::Range<char**> rows) {
   if (!nextOffset_ || !hasDuplicateRows_) {
     return;
   }
 
-  if (clear) {
-    for (auto row : rows) {
-      auto vector = getNextRowVector(row);
-      if (vector) {
-        // Clear all rows, we can clear the nextOffset_ slots and delete the
-        // next-row-vector.
-        for (auto& next : *vector) {
-          getNextRowVector(next) = nullptr;
-        }
-        // Because of 'parallelJoinBuild', the memory for the next row vector
-        // may not be allocated from the RowContainer to which the row belongs,
-        // hence we need to release memory through the vector's allocator.
-        auto allocator = vector->get_allocator().allocator();
-        std::destroy_at(vector);
-        allocator->free(HashStringAllocator::headerOf(vector));
-      }
-    }
-    return;
-  }
-
   for (auto row : rows) {
     auto vector = getNextRowVector(row);
     if (vector) {
@@ -500,10 +480,14 @@ void RowContainer::freeNextRowVectors(folly::Range<char**> rows, bool clear) {
   }
 }
 
-void RowContainer::freeRowsExtraMemory(folly::Range<char**> rows, bool clear) {
+void RowContainer::freeRowsExtraMemory(
+    folly::Range<char**> rows,
+    bool freeNextRowVector) {
   freeVariableWidthFields(rows);
   freeAggregates(rows);
-  freeNextRowVectors(rows, clear);
+  if (freeNextRowVector) {
+    freeNextRowVectors(rows);
+  }
   numRows_ -= rows.size();
 }
 
@@ -959,7 +943,9 @@ void RowContainer::clear() {
     std::vector<char*> rows(kBatch);
     RowContainerIterator iter;
     while (auto numRows = listRows(&iter, kBatch, rows.data())) {
-      freeRowsExtraMemory(folly::Range<char**>(rows.data(), numRows), true);
+      freeRowsExtraMemory(
+          folly::Range<char**>(rows.data(), numRows),
+          /*freeNextRowVector=*/false);
     }
   }
   hasDuplicateRows_ = false;

velox/exec/RowContainer.h

@@ -1368,9 +1368,9 @@ class RowContainer {
   void freeAggregates(folly::Range<char**> rows);
 
   // Free next row vectors associated with the 'rows'.
-  void freeNextRowVectors(folly::Range<char**> rows, bool clear);
+  void freeNextRowVectors(folly::Range<char**> rows);
 
-  void freeRowsExtraMemory(folly::Range<char**> rows, bool clear);
+  void freeRowsExtraMemory(folly::Range<char**> rows, bool freeNextRowVector);
 
   // Updates the specific column's columnHasNulls_ flag, if 'hasNulls' is true.
   // columnHasNulls_ flag is false by default.