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https://issues.apache.org/jira/browse/FLINK-7243?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16645660#comment-16645660
]
ASF GitHub Bot commented on FLINK-7243:
---------------------------------------
fhueske commented on a change in pull request #6483:
[FLINK-7243][flink-formats] Add parquet input format
URL: https://github.com/apache/flink/pull/6483#discussion_r224235315
##########
File path:
flink-formats/flink-parquet/src/main/java/org/apache/flink/formats/parquet/ParquetInputFormat.java
##########
@@ -0,0 +1,241 @@
+/*
+ * 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.flink.formats.parquet;
+
+import org.apache.flink.api.common.io.CheckpointableInputFormat;
+import org.apache.flink.api.common.io.FileInputFormat;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.typeutils.RowTypeInfo;
+import org.apache.flink.core.fs.FileInputSplit;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.formats.parquet.utils.ParquetRecordReader;
+import org.apache.flink.formats.parquet.utils.ParquetSchemaConverter;
+import org.apache.flink.formats.parquet.utils.RowReadSupport;
+import org.apache.flink.metrics.Counter;
+import org.apache.flink.types.Row;
+import org.apache.flink.util.Preconditions;
+
+import org.apache.parquet.ParquetReadOptions;
+import org.apache.parquet.filter2.compat.FilterCompat;
+import org.apache.parquet.hadoop.ParquetFileReader;
+import org.apache.parquet.hadoop.util.HadoopInputFile;
+import org.apache.parquet.io.InputFile;
+import org.apache.parquet.schema.MessageType;
+import org.apache.parquet.schema.Type;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * The base InputFormat class to read from Parquet files.
+ * For specific return types the {@link #convert(Row)} method need to be
implemented.
+ *
+ * <P>Using {@link ParquetRecordReader} to read files instead of {@link
org.apache.flink.core.fs.FSDataInputStream},
+ * we override {@link #open(FileInputSplit)} and {@link #close()} to change
the behaviors.
+ *
+ * @param <E> The type of record to read.
+ */
+public abstract class ParquetInputFormat<E>
+ extends FileInputFormat<E>
+ implements CheckpointableInputFormat<FileInputSplit, Tuple2<Long,
Long>> {
+
+ private static final long serialVersionUID = 1L;
+
+ private static final Logger LOG =
LoggerFactory.getLogger(ParquetInputFormat.class);
+
+ private transient Counter recordConsumed;
+
+ private final TypeInformation[] fieldTypes;
+
+ private final String[] fieldNames;
+
+ private boolean skipThisSplit = false;
+
+ private transient ParquetRecordReader<Row> parquetRecordReader;
+
+ private transient long recordsReadSinceLastSync;
+
+ private long lastSyncedBlock = -1L;
+
+ /**
+ * Read parquet files with given result parquet schema.
+ *
+ * @param path The path of the file to read.
+ * @param messageType schema of read result
+ */
+
+ protected ParquetInputFormat(Path path, MessageType messageType) {
+ super(path);
+ RowTypeInfo readType = (RowTypeInfo)
ParquetSchemaConverter.fromParquetType(messageType);
+ this.fieldTypes = readType.getFieldTypes();
Review comment:
This uses the message type to define which fields to read but not the
overall schema of the files. In my earlier comments I was thinking of something
like this:
```
// define input format with full schema of files (in whatever Schema
representation Parquet uses).
ParquetRowInputFormat pif = new ParquetRowInputFormat(new Path(...), "name:
String, age: Int, city: String, ...");
// select which fields to read. This is used to build the readSchema.
pif.selectFields("city", "name");
```
The idea is similar to DDL in a DBMS. The input format is defined with all
fields and later is selected which fields to read. This should be useful,
because the full Parquet schema should be usually available and when selecting
the field to read, we would not need to specify the types but just the field
names.
What do you think?
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> Add ParquetInputFormat
> ----------------------
>
> Key: FLINK-7243
> URL: https://issues.apache.org/jira/browse/FLINK-7243
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: godfrey he
> Assignee: Zhenqiu Huang
> Priority: Major
> Labels: pull-request-available
>
> Add a {{ParquetInputFormat}} to read data from a Apache Parquet file.
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