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/*
* Copyright (c) 2021 AtLarge Research
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package org.opendc.trace.util.parquet
import org.apache.parquet.hadoop.ParquetReader
import org.apache.parquet.hadoop.api.ReadSupport
import org.apache.parquet.io.InputFile
import java.io.File
import java.io.IOException
import java.nio.file.Files
import java.nio.file.Path
import kotlin.io.path.isDirectory
/**
* A helper class to read Parquet files from the filesystem.
*
* This class wraps a [ParquetReader] in order to support reading partitioned Parquet datasets.
*
* @param path The path to the Parquet file or directory to read.
* @param readSupport Helper class to perform conversion from Parquet to [T].
* @param strictTyping A flag to disable strict typing of primitive types.
*/
public class LocalParquetReader<out T>(
path: Path,
private val readSupport: ReadSupport<T>,
private val strictTyping: Boolean = true,
) : AutoCloseable {
/**
* The input files to process.
*/
private val filesIterator =
if (path.isDirectory()) {
Files.list(path)
.filter { !it.isDirectory() }
.sorted()
.map { LocalInputFile(it) }
.iterator()
} else {
listOf(LocalInputFile(path)).iterator()
}
/**
* The Parquet reader to use.
*/
private var reader: ParquetReader<T>? = null
/**
* Construct a [LocalParquetReader] for the specified [file].
*/
public constructor(file: File, readSupport: ReadSupport<T>) : this(file.toPath(), readSupport)
/**
* Read a single entry in the Parquet file.
*/
public fun read(): T? {
return try {
val next = reader?.read()
if (next != null) {
next
} else {
initReader()
if (reader == null) {
null
} else {
read()
}
}
} catch (e: InterruptedException) {
throw IOException(e)
}
}
/**
* Close the Parquet reader.
*/
override fun close() {
reader?.close()
}
/**
* Initialize the next reader.
*/
private fun initReader() {
reader?.close()
try {
this.reader =
if (filesIterator.hasNext()) {
createReader(filesIterator.next())
} else {
null
}
} catch (e: Throwable) {
this.reader = null
throw e
}
}
/**
* Construct a [ParquetReader] for the specified [input] with a custom [ReadSupport].
*/
private fun createReader(input: InputFile): ParquetReader<T> {
return object : ParquetReader.Builder<T>(input) {
override fun getReadSupport(): ReadSupport<@UnsafeVariance T> = this@LocalParquetReader.readSupport
}
.set("parquet.strict.typing", strictTyping.toString())
.build()
}
}
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