Cannot read row group larger than 2GB
- 主要语言
- Java
- 星标
- 3.1k
- 派生
- 1.6k
- 平均合并
- 3 天 12 小时
- 30 天内合并 PR
- 33
描述
Parquet MR 1.8.2 does not support reading row groups which are larger than 2 GB. See:https://github.com/apache/parquet-mr/blob/parquet-1.8.x/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java#L1064
We are seeing this when writing skewed records. This throws off the estimation of the memory check interval in the InternalParquetRecordWriter. The following spark code illustrates this:
```
/**
* Create a data frame that will make parquet write a file with a row group larger than 2 GB. Parquet
* only checks the size of the row group after writing a number of records. This number is based on
* average row size of the already written records. This is problematic in the following scenario:
* - The initial (100) records in the record group are relatively small.
* - The InternalParquetRecordWriter checks if it needs to write to disk (it should not), it assumes
* that the remaining records have a similar size, and (greatly) increases the check interval (usually
* to 10000).
* - The remaining records are much larger then expected, making the row group larger than 2 GB (which
* makes reading the row group impossible).
*
* The data frame below illustrates such a scenario. This creates a row group of approximately 4GB.
*/
val badDf = spark.range(0, 2200, 1, 1).mapPartitions { iterator =>
var i = 0
val random = new scala.util.Random(42)
val buffer = new Array[Char](750000)
iterator.map { id =>
// the first 200 records have a length of 1K and the remaining 2000 have a length of 750K.
val numChars = if (i < 200) 1000 else 750000
i += 1
// create a random array
var j = 0
while (j < numChars) {
// Generate a char (borrowed from scala.util.Random)
buffer(j) = (random.nextInt(0xD800 - 1) + 1).toChar
j += 1
}
// create a string: the string constructor will copy the buffer.
new String(buffer, 0, numChars)
}
}
badDf.write.parquet("somefile")
val corruptedDf = spark.read.parquet("somefile")
corruptedDf.select(count(lit(1)), max(length($"value"))).show()
```
The latter fails with the following exception:
```
java.lang.NegativeArraySizeException
at org.apache.parquet.hadoop.ParquetFileReader$ConsecutiveChunkList.readAll(ParquetFileReader.java:1064)
at org.apache.parquet.hadoop.ParquetFileReader.readNextRowGroup(ParquetFileReader.java:698)
...
```
-This seems to be fixed by commit https://github.com/apache/parquet-mr/commit/6b605a4ea05b66e1a6bf843353abcb4834a4ced8 in parquet 1.9.x. Is there any chance that we can fix this in 1.8.x?-
**Reporter**: [Herman van Hövell](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=hvanhovell)
**Note**: *This issue was originally created as [PARQUET-980](https://issues.apache.org/jira/browse/PARQUET-980). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*
贡献指南
这个仓库没有索引到贡献指南
调研方向
从 parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java 第 1064 行开始,并将其行为与 commit 6b605a4ea05b66e1a6bf843353abcb4834a4ced8 进行比较。使用报告中的 Spark 示例重现该问题,然后验证 parquet 1.8.x 能够读取生成的 row group,且不会出现 NegativeArraySizeException。
由索引模型根据 Issue 内容生成。
评估
- 技术栈
- java, scala
- 领域
- data-engineering
- Issue 类型
- 缺陷
- 难度
- 4/5
- 预计耗时
- 3-5 天
- 活跃度
- 停滞
- 描述清晰度
- 描述清楚
- 新手友好度
- 35/100