add log in offset operator

server/src/main/java/org/apache/iotdb/db/mpp/execution/operator/process/OffsetOperator.java

diff --git a/server/src/main/java/org/apache/iotdb/db/mpp/execution/operator/process/OffsetOperator.java b/server/src/main/java/org/apache/iotdb/db/mpp/execution/operator/process/OffsetOperator.java
index 37127e8..debd350 100644
--- a/server/src/main/java/org/apache/iotdb/db/mpp/execution/operator/process/OffsetOperator.java
+++ b/server/src/main/java/org/apache/iotdb/db/mpp/execution/operator/process/OffsetOperator.java
@@ -23,12 +23,16 @@
 import org.apache.iotdb.tsfile.read.common.block.TsBlock;
 
 import com.google.common.util.concurrent.ListenableFuture;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static java.util.Objects.requireNonNull;
 
 public class OffsetOperator implements ProcessOperator {
 
+  private static final Logger LOGGER = LoggerFactory.getLogger(OffsetOperator.class);
+
   private final OperatorContext operatorContext;
   private long remainingOffset;
   private final Operator child;
@@ -59,6 +63,7 @@
     if (remainingOffset > 0) {
       int offset = Math.min((int) remainingOffset, block.getPositionCount());
       remainingOffset -= offset;
+      LOGGER.info("current remaining offset: {}", remainingOffset);
       return block.getRegion(offset, block.getPositionCount() - offset);
     } else {
       return block;