[GitHub] arina-ielchiieva commented on a change in pull request #1618: DRILL-6950: Row set-based scan framework

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arina-ielchiieva commented on a change in pull request #1618: DRILL-6950: Row set-based scan framework
URL: https://github.com/apache/drill/pull/1618#discussion_r250575132
 
 

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 File path: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/scan/ReaderState.java
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+/*
+ * 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.physical.impl.scan;
+
+import org.apache.drill.common.exceptions.UserException;
+import org.apache.drill.exec.record.VectorContainer;
+
+/**
+ * Manages a row batch reader through its lifecycle. Created when the reader
+ * is opened, discarded when the reader is closed. Encapsulates state that
+ * follows the life of the reader. This moves common scanner state out of
+ * each reader in order to make the reader as simple as possible.
+ * <p>
+ * This class is private to the scan operator and is not meant to be used,
+ * or even visible, outside of that operator itself. Instead, all reader-specific
+ * functionality should be in the {@link RowBatchReader} subclass.
+ */
+
+class ReaderState {
+  static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ReaderState.class);
+
+  private enum State { START, LOOK_AHEAD, LOOK_AHEAD_WITH_EOF, ACTIVE, EOF, CLOSED };
 
 Review comment:
   Could you please add java-doc for each state, describing its purpose?

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