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https://issues.apache.org/jira/browse/DRILL-5356?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15959866#comment-15959866
]
ASF GitHub Bot commented on DRILL-5356:
---------------------------------------
Github user ppadma commented on a diff in the pull request:
https://github.com/apache/drill/pull/789#discussion_r110266898
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/columnreaders/BatchReader.java
---
@@ -0,0 +1,164 @@
+/*
+ * 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.parquet.columnreaders;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+import com.google.common.base.Stopwatch;
+import com.google.common.collect.Lists;
+
+/**
+ * Base strategy for reading a batch of Parquet records.
+ */
+public abstract class BatchReader {
+
+ protected final ReadState readState;
+
+ public BatchReader(ReadState readState) {
+ this.readState = readState;
+ }
+
+ public int readBatch() throws Exception {
+ ColumnReader<?> firstColumnStatus = readState.getFirstColumnReader();
+ long recordsToRead = Math.min(getReadCount(firstColumnStatus),
readState.getRecordsToRead());
+ int readCount = readRecords(firstColumnStatus, recordsToRead);
+ readState.fillNullVectors(readCount);
+ return readCount;
+ }
+
+ protected abstract long getReadCount(ColumnReader<?> firstColumnStatus);
+
+ protected abstract int readRecords(ColumnReader<?> firstColumnStatus,
long recordsToRead) throws Exception;
+
+ protected void readAllFixedFields(long recordsToRead) throws Exception {
+ Stopwatch timer = Stopwatch.createStarted();
+ if(readState.useAsyncColReader()){
+ readAllFixedFieldsParallel(recordsToRead);
+ } else {
+ readAllFixedFieldsSerial(recordsToRead);
+ }
+
readState.parquetReaderStats().timeFixedColumnRead.addAndGet(timer.elapsed(TimeUnit.NANOSECONDS));
+ }
+
+ protected void readAllFixedFieldsSerial(long recordsToRead) throws
IOException {
+ for (ColumnReader<?> crs : readState.getColumnReaders()) {
+ crs.processPages(recordsToRead);
+ }
+ }
+
+ protected void readAllFixedFieldsParallel(long recordsToRead) throws
Exception {
+ ArrayList<Future<Long>> futures = Lists.newArrayList();
+ for (ColumnReader<?> crs : readState.getColumnReaders()) {
+ Future<Long> f = crs.processPagesAsync(recordsToRead);
+ futures.add(f);
+ }
+ Exception exception = null;
+ for(Future<Long> f: futures){
+ if (exception != null) {
+ f.cancel(true);
+ } else {
+ try {
+ f.get();
+ } catch (Exception e) {
+ f.cancel(true);
+ exception = e;
+ }
+ }
+ }
+ if (exception != null) {
+ throw exception;
+ }
+ }
+
+ /**
+ * Strategy for reading mock records. (What are these?)
+ */
--- End diff --
Please add brief explanation what these are instead of "what are these ?"
> Refactor Parquet Record Reader
> ------------------------------
>
> Key: DRILL-5356
> URL: https://issues.apache.org/jira/browse/DRILL-5356
> Project: Apache Drill
> Issue Type: Improvement
> Affects Versions: 1.10.0, 1.11.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Priority: Minor
> Fix For: 1.11.0
>
>
> The Parquet record reader class is a key part of Drill that has evolved over
> time to become somewhat hard to follow.
> A number of us are working on Parquet-related tasks and find we have to spend
> an uncomfortable amount of time trying to understand the code. In particular,
> this writer needs to figure out how to convince the reader to provide
> higher-density record batches.
> Rather than continue to decypher the complex code multiple times, this ticket
> requests to refactor the code to make it functionally identical, but
> structurally cleaner. The result will be faster time to value when working
> with this code.
> This is a lower-priority change and will be coordinated with others working
> on this code base. This ticket is only for the record reader class itself; it
> does not include the various readers and writers that Parquet uses since
> another project is actively modifying those classes.
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