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https://issues.apache.org/jira/browse/DRILL-7442?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16972341#comment-16972341
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ASF GitHub Bot commented on DRILL-7442:
---------------------------------------
vvysotskyi commented on pull request #1897: DRILL-7442: Create multi-batch row
set reader
URL: https://github.com/apache/drill/pull/1897#discussion_r345174090
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/physical/resultSet/ResultSetReader.java
##########
@@ -0,0 +1,50 @@
+/*
+ * 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.resultSet;
+
+import org.apache.drill.exec.physical.impl.protocol.BatchAccessor;
+import org.apache.drill.exec.physical.rowSet.RowSetReader;
+
+/**
+ * Iterates over the set of batches in a result set, providing
+ * a row set reader to iterate over the rows within each batch.
+ * Handles schema changes between batches.
+ * <h4>Protocol</h4>
+ * <ol>
+ * <li>Create an instance.</li>
+ * <li>For each incoming batch:
+ * <ol>
+ * <li>Call {@link #start()} to attach the batch. The provided
+ * {@link BatchAccessor} reports if the schema has changed.</li>
+ * <li>Call {@link #reader()} to obtain a reader.</li>
+ * <li>Iterate over the batch using the reader.</li>
+ * <li>Call {@link #release()} to free the memory for the
+ * incoming batch. Or, to call {@link #detach()} to keep
+ * the batch memory.</li>
+ * </ol>
+ * <li>Call {@link #close()} after all batches are read.</li>
+ * </ol>
+ */
+public interface ResultSetReader {
+
+ void start(BatchAccessor batch);
Review comment:
Could you please add JavaDocs to these methods. Though their purposes are
described in the class JavaDoc, it would be handy also to have their own ones.
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> Create multi-batch row set reader
> ---------------------------------
>
> Key: DRILL-7442
> URL: https://issues.apache.org/jira/browse/DRILL-7442
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
>
> The "row set" work provided a {{RowSetWriter}} and {{RowSetReader}} to write
> to and read from a single batch. The {{ResultSetLoader}} class provided a
> writer that spans multiple batches, handling schema changes across batches
> and so on.
> This ticket introduces a reader equivalent, the {{ResultSetReader}} that
> reads an entire result set of multiple batches, handling schema changes along
> the way.
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