Hi all,
Looks like data frame parquet writing is very broken in Spark 1.4.0. We had no
problems with Spark 1.3.
When trying to save a data frame with 569610608 rows.
dfc.write.format("parquet").save(“/data/map_parquet_file")
We get random results between runs. Caching the data frame in memory makes no
difference. It looks like the write out misses some of the RDD partitions. We
have an RDD with 6750 partitions. When we write out we get less files out than
the number of partitions. When reading the data back in and running a count, we
get smaller number of rows.
I’ve tried counting the rows in all different ways. All return the same result,
560214031 rows, missing about 9.4 million rows (0.15%).
qc.read.parquet("/data/map_parquet_file").count
qc.read.parquet("/data/map_parquet_file").rdd.count
qc.read.parquet("/data/map_parquet_file").mapPartitions{itr => var c = 0;
itr.foreach(_ => c = c + 1); Seq(c).toIterator }.reduce(_ + _)
Looking on HDFS the files, there are 6643 .parquet files. 107 missing
partitions (about 0.15%).
Then writing out the same cached DF again to a new file gives 6717 files on
hdfs (about 33 files missing or 0.5%);
dfc.write.parquet(“/data/map_parquet_file_2")
And we get 566670107 rows back (about 3million missing ~0.5%);
qc.read.parquet("/data/map_parquet_file_2").count
Writing the same df out to json writes the expected number (6750) of parquet
files and returns the right number of rows 569610608.
dfc.write.format("json").save("/data/map_parquet_file_3")
qc.read.format("json").load("/data/map_parquet_file_3").count
One thing to note is that the parquet part files on HDFS are not the normal
sequential part numbers like for the json output and parquet output in Spark
1.3.
part-r-06151.gz.parquet part-r-118401.gz.parquet part-r-146249.gz.parquet
part-r-196755.gz.parquet part-r-35811.gz.parquet part-r-55628.gz.parquet
part-r-73497.gz.parquet part-r-97237.gz.parquet
part-r-06161.gz.parquet part-r-118406.gz.parquet part-r-146254.gz.parquet
part-r-196763.gz.parquet part-r-35826.gz.parquet part-r-55647.gz.parquet
part-r-73500.gz.parquet _SUCCESS
We are using MapR 4.0.2 for hdfs.
Any ideas?
Cheers,
Nathan
