From 181271716cae5baf4f91ee320e497b14dd557a71 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nacho=20Cord=C3=B3n?= <nacho.cordon@neotechnology.com>
Date: Wed, 1 Nov 2023 11:48:14 +0000
Subject: [PATCH] [jMd3ZuqI] Fixes arrow stream strategy

---
 .../arrow/ExportArrowStreamStrategy.java      | 60 ++++++++++++-------
 1 file changed, 39 insertions(+), 21 deletions(-)

diff --git a/core/src/main/java/apoc/export/arrow/ExportArrowStreamStrategy.java b/core/src/main/java/apoc/export/arrow/ExportArrowStreamStrategy.java
index ebf8d2d2e..73b2bad24 100644
--- a/core/src/main/java/apoc/export/arrow/ExportArrowStreamStrategy.java
+++ b/core/src/main/java/apoc/export/arrow/ExportArrowStreamStrategy.java
@@ -20,8 +20,6 @@
 
 import apoc.convert.Json;
 import apoc.result.ByteArrayResult;
-import apoc.util.QueueBasedSpliterator;
-import apoc.util.QueueUtil;
 import apoc.util.Util;
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.vector.VectorSchemaRoot;
@@ -38,8 +36,6 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.concurrent.ArrayBlockingQueue;
-import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
@@ -72,34 +68,56 @@ default byte[] writeBatch(BufferAllocator bufferAllocator, List<Map<String, Obje
     }
 
     default Stream<ByteArrayResult> export(IN data, ArrowConfig config) {
-        final BlockingQueue<ByteArrayResult> queue = new ArrayBlockingQueue<>(100);
-        Util.inTxFuture(getExecutorService(), getGraphDatabaseApi(), txInThread -> {
+        class ExportIterator implements Iterator<ByteArrayResult> {
+            ByteArrayResult current;
             int batchCount = 0;
-            List<Map<String, Object>> rows = new ArrayList<>(config.getBatchSize());
-            try {
-                Iterator<Map<String, Object>> it = toIterator(data);
-                while (!Util.transactionIsTerminated(getTerminationGuard()) && it.hasNext()) {
+            Iterator<Map<String, Object>> it;
+
+            public ExportIterator(IN data) {
+                it = toIterator(data);
+                current = null;
+                computeBatch();
+            }
+
+            @Override
+            public boolean hasNext()
+            {
+                return current != null;
+            }
+
+            @Override
+            public ByteArrayResult next()
+            {
+                ByteArrayResult result = current;
+                current = null;
+                computeBatch();
+                return result;
+            }
+
+            private void computeBatch() {
+                boolean keepIterating = true;
+                List<Map<String, Object>> rows = new ArrayList<>(config.getBatchSize());
+
+                while (!Util.transactionIsTerminated(getTerminationGuard()) && it.hasNext() && keepIterating) {
                     rows.add(it.next());
                     if (batchCount > 0 && batchCount % config.getBatchSize() == 0) {
                         final byte[] bytes = writeBatch(getBufferAllocator(), rows);
-                        QueueUtil.put(queue, new ByteArrayResult(bytes), 10);
-                        rows.clear();
+                        current = new ByteArrayResult(bytes);
+                        keepIterating = false;
                     }
                     ++batchCount;
                 }
+
                 if (!rows.isEmpty()) {
                     final byte[] bytes = writeBatch(getBufferAllocator(), rows);
-                    QueueUtil.put(queue, new ByteArrayResult(bytes), 10);
+                    current = new ByteArrayResult(bytes);
                 }
-            } catch (Exception e) {
-                getLogger().error("Exception while extracting Arrow data:", e);
-            } finally {
-                QueueUtil.put(queue, ByteArrayResult.NULL, 10);
             }
-            return true;
-        });
-        QueueBasedSpliterator<ByteArrayResult> spliterator = new QueueBasedSpliterator<>(queue, ByteArrayResult.NULL, getTerminationGuard(), Integer.MAX_VALUE);
-        return StreamSupport.stream(spliterator, false);
+        }
+
+        var streamIterator = new ExportIterator(data);
+        Iterable<ByteArrayResult> iterable = () -> streamIterator;
+        return StreamSupport.stream(iterable.spliterator(), false);
     }
 
     default Object convertValue(Object data) {