Added offset tracker

contrib/storage-druid/src/main/java/org/apache/drill/exec/store/druid/DruidBatchRecordReader.java

@@ -51,8 +51,7 @@ public class DruidBatchRecordReader implements ManagedReader<SchemaNegotiator> {
   private final List<String> columns;
   private final DruidFilter filter;
   private final DruidQueryClient druidQueryClient;
-
-  private BigInteger nextOffset = BigInteger.ZERO;
+  private final DruidOffsetTracker offsetTracker;
   private int maxRecordsToRead = -1;
   private JsonLoaderBuilder jsonBuilder;
   private JsonLoaderImpl jsonLoader;
@@ -64,13 +63,14 @@ public DruidBatchRecordReader(DruidSubScan subScan,
                                 DruidSubScanSpec subScanSpec,
                                 List<SchemaPath> projectedColumns,
                                 int maxRecordsToRead,
-                                DruidStoragePlugin plugin) {
+                                DruidStoragePlugin plugin, DruidOffsetTracker offsetTracker) {
     this.columns = new ArrayList<>();
     this.maxRecordsToRead = maxRecordsToRead;
     this.plugin = plugin;
     this.scanSpec = subScanSpec;
     this.filter = subScanSpec.getFilter();
     this.druidQueryClient = plugin.getDruidQueryClient();
+    this.offsetTracker = offsetTracker;
   }
 
   @Override
@@ -118,10 +118,6 @@ public void close() {
       jsonLoader.close();
       jsonLoader = null;
     }
-
-    if (! nextOffset.equals(BigInteger.ZERO)) {
-      nextOffset = BigInteger.ZERO;
-    }
   }
 
   private String getQuery() throws JsonProcessingException {
@@ -135,7 +131,7 @@ private String getQuery() throws JsonProcessingException {
         scanSpec.dataSourceName,
         columns,
         filter,
-        nextOffset,
+        offsetTracker.getOffset(),
         queryThreshold,
         scanSpec.getMinTime(),
         scanSpec.getMaxTime()
@@ -144,6 +140,7 @@ private String getQuery() throws JsonProcessingException {
   }
 
   private void setNextOffset(DruidScanResponse druidScanResponse) {
-    nextOffset = nextOffset.add(BigInteger.valueOf(druidScanResponse.getEvents().size()));
+    //nextOffset = nextOffset.add(BigInteger.valueOf(druidScanResponse.getEvents().size()));
+    offsetTracker.setNextOffset(BigInteger.valueOf(druidScanResponse.getEvents().size()));
   }
 }

contrib/storage-druid/src/main/java/org/apache/drill/exec/store/druid/DruidOffsetTracker.java

@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.exec.store.druid;
+
+import java.math.BigInteger;
+
+public class DruidOffsetTracker {
+  private BigInteger nextOffset;
+
+  public DruidOffsetTracker() {
+    this.nextOffset = BigInteger.ZERO;
+  }
+
+  public BigInteger getOffset() {
+    return nextOffset;
+  }
+
+  public void setNextOffset(BigInteger offset) {
+    nextOffset = nextOffset.add(offset);
+  }
+}

contrib/storage-druid/src/main/java/org/apache/drill/exec/store/druid/DruidScanBatchCreator.java

@@ -72,12 +72,13 @@ private ScanFrameworkBuilder createBuilder(OptionManager options, DruidSubScan s
 
   private static class DruidReaderFactory implements ReaderFactory {
     private final DruidSubScan subScan;
-
+    private final DruidOffsetTracker offsetTracker;
     private final Iterator<DruidSubScanSpec> scanSpecIterator;
 
     public DruidReaderFactory(DruidSubScan subScan) {
       this.subScan = subScan;
       this.scanSpecIterator = subScan.getScanSpec().listIterator();
+      this.offsetTracker = new DruidOffsetTracker();
     }
 
     @Override
@@ -89,7 +90,7 @@ public void bind(ManagedScanFramework framework) {
     public ManagedReader<? extends SchemaNegotiator> next() {
       if (scanSpecIterator.hasNext()) {
         DruidSubScanSpec scanSpec = scanSpecIterator.next();
-        return new DruidBatchRecordReader(subScan, scanSpec, subScan.getColumns(), subScan.getMaxRecordsToRead(), subScan.getStorageEngine());
+        return new DruidBatchRecordReader(subScan, scanSpec, subScan.getColumns(), subScan.getMaxRecordsToRead(), subScan.getStorageEngine(), offsetTracker);
       }
       return null;
     }