Our bulk insert(not just bulk insert, all operations infact) does dataset to rdd conversion in HoodieSparkSqlWriter and our HoodieClient deals with JavaRDD<HoodieRecord>s. We are trying to see if we can improve our performance by avoiding the rdd conversion. We will first start off w/ bulk insert and get end to end working before we decide if we wanna do this for other operations too after doing some perf analysis.
On a high level, this is the idea
1. Dataset<Row> will be passed in all the way from spark sql writer to the storage writer. We do not convert to HoodieRecord at any point in time.
2. We need to use [ParquetWriteSupport|https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetWriteSupport.scala] to write to Parquet as InternalRows.
3. So, gist of what we wanna do is, with the Dataset<Rows>s, sort by partition path and record keys, repartition by parallelism config, and do mapPartitions. Within MapPartitions, we will iterate through the Rows, encode to InternalRows and write to Parquet using the write support linked above.
We first wanted to check if our strategy will actually improve the perf. So, I did a quick hack of just the mapPartition func in HoodieSparkSqlWriter just to see how the numbers look like. Check for operation "bulk_insert_direct_parquet_write_support" here].
These are the numbers I got. (1) is existing hoodie bulk insert which does the rdd conversion to JavaRdd<HoodieRecords>. (2) is writing directly to parquet in spark. Code given below. (3) is the modified hoodie code i.e. operation bulk_insert_direct_parquet_write_support)
|5M records 100 parallelism input size 2.5 GB|
|(1) Orig hoodie(unmodified)||169 secs. output size 2.7 GB|
|(2) Parquet||62 secs. output size 2.5 GB|
|(3) Modified hudi code. Direct Parquet Write||73 secs. output size 2.5 GB|
So, essentially our existing code for bulk insert is > 2x that of parquet. Our modified hudi code (i.e. operation bulk_insert_direct_parquet_write_support) is close to direct Parquet write in spark, which shows that our strategy should work.
// This is the Parquet write in spark. (2) above.