[DISCUSS] Support subdirectories when accessing partitioned Parquet Hive table

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[DISCUSS] Support subdirectories when accessing partitioned Parquet Hive table

Lotkowski, Michael

Hi all,

 

Reviving this thread, we still have this issue and we have been using our updated jar which seems to work. It would be great to get some feedback whether this is the correct approach.

 

Kind regards,

Michael

 

From: "Lotkowski, Michael" <[hidden email]>
Date: Tuesday, December 3, 2019 at 10:28 AM
To: "[hidden email]" <[hidden email]>
Subject: Support subdirectories when accessing partitioned Parquet Hive table

 

Originally https://issues.apache.org/jira/browse/SPARK-30024

 

Hi all,

We have ran in to issues when trying to read parquet partitioned table created by Hive. I think I have narrowed down the cause to how InMemoryFileIndex created a parent -> file mapping.

The folder structure created by Hive is as follows:

s3://bucket/table/date=2019-11-25/subdir1/data1.parquet

s3://bucket/table/date=2019-11-25/subdir2/data2.parquet

Looking through the code it seems that InMemoryFileIndex is creating a mapping of leaf files to their parents yielding the following mapping:

 val leafDirToChildrenFiles = Map(

    s3://bucket/table/date=2019-11-25/subdir1 -> s3://bucket/table/date=2019-11-25/subdir1/data1.parquet,

    s3://bucket/table/date=2019-11-25/subdir2 -> s3://bucket/table/date=2019-11-25/subdir2/data2.parquet

)

Which then in turn is used in PartitioningAwareFileIndex

to prune the partitions. From my understanding pruning works by looking up the partition path in leafDirToChildrenFiles which in this case is s3://bucket/table/date=2019-11-25/ and therefore it fails to find any files for this partition.

My suggested fix is to update how the InMemoryFileIndex builds the mapping, instead of having a map between parent dir to file, is to have a map of rootPath to file. More concretely https://gist.github.com/lotkowskim/76e8ff265493efd0b2b7175446805a82

I have tested this by updating the jar running on EMR and we correctly can now read the data from these partitioned tables. It's also worth noting that we can read the data, without any modifications to the code, if we use the following settings:

"spark.sql.hive.convertMetastoreParquet" to "false",
"spark.hive.mapred.supports.subdirectories" to "true",
"spark.hadoop.mapreduce.input.fileinputformat.input.dir.recursive" to "true"

However with these settings we lose the ability to prune partitions causing us to read the entire table every time as we aren't using a Spark relation.

I want to start discussion on whether this is a correct change, or if we are missing something more obvious. In either case I would be happy to fully implement the change.

Thanks,

Michael

 




Amazon Development Centre (Scotland) Limited registered office: Waverley Gate, 2-4 Waterloo Place, Edinburgh EH1 3EG, Scotland. Registered in Scotland Registration number SC26867






Amazon Development Centre (Scotland) Limited registered office: Waverley Gate, 2-4 Waterloo Place, Edinburgh EH1 3EG, Scotland. Registered in Scotland Registration number SC26867


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Re: [DISCUSS] Support subdirectories when accessing partitioned Parquet Hive table

cloud0fan
Isn't your directory structure malformed? The directory name under the table path should be in the form of "partitionCol=value". And AFAIK this is the Hive standard.



On Mon, Jan 6, 2020 at 6:59 PM Lotkowski, Michael <[hidden email]> wrote:

Hi all,

 

Reviving this thread, we still have this issue and we have been using our updated jar which seems to work. It would be great to get some feedback whether this is the correct approach.

 

Kind regards,

Michael

 

From: "Lotkowski, Michael" <[hidden email]>
Date: Tuesday, December 3, 2019 at 10:28 AM
To: "[hidden email]" <[hidden email]>
Subject: Support subdirectories when accessing partitioned Parquet Hive table

 

Originally https://issues.apache.org/jira/browse/SPARK-30024

 

Hi all,

We have ran in to issues when trying to read parquet partitioned table created by Hive. I think I have narrowed down the cause to how InMemoryFileIndex created a parent -> file mapping.

The folder structure created by Hive is as follows:

s3://bucket/table/date=2019-11-25/subdir1/data1.parquet

s3://bucket/table/date=2019-11-25/subdir2/data2.parquet

Looking through the code it seems that InMemoryFileIndex is creating a mapping of leaf files to their parents yielding the following mapping:

 val leafDirToChildrenFiles = Map(

    s3://bucket/table/date=2019-11-25/subdir1 -> s3://bucket/table/date=2019-11-25/subdir1/data1.parquet,

    s3://bucket/table/date=2019-11-25/subdir2 -> s3://bucket/table/date=2019-11-25/subdir2/data2.parquet

)

Which then in turn is used in PartitioningAwareFileIndex

to prune the partitions. From my understanding pruning works by looking up the partition path in leafDirToChildrenFiles which in this case is s3://bucket/table/date=2019-11-25/ and therefore it fails to find any files for this partition.

My suggested fix is to update how the InMemoryFileIndex builds the mapping, instead of having a map between parent dir to file, is to have a map of rootPath to file. More concretely https://gist.github.com/lotkowskim/76e8ff265493efd0b2b7175446805a82

I have tested this by updating the jar running on EMR and we correctly can now read the data from these partitioned tables. It's also worth noting that we can read the data, without any modifications to the code, if we use the following settings:

"spark.sql.hive.convertMetastoreParquet" to "false",
"spark.hive.mapred.supports.subdirectories" to "true",
"spark.hadoop.mapreduce.input.fileinputformat.input.dir.recursive" to "true"

However with these settings we lose the ability to prune partitions causing us to read the entire table every time as we aren't using a Spark relation.

I want to start discussion on whether this is a correct change, or if we are missing something more obvious. In either case I would be happy to fully implement the change.

Thanks,

Michael

 




Amazon Development Centre (Scotland) Limited registered office: Waverley Gate, 2-4 Waterloo Place, Edinburgh EH1 3EG, Scotland. Registered in Scotland Registration number SC26867






Amazon Development Centre (Scotland) Limited registered office: Waverley Gate, 2-4 Waterloo Place, Edinburgh EH1 3EG, Scotland. Registered in Scotland Registration number SC26867