Costi Muraru created PARQUET-964:
------------------------------------
Summary: Using ProtoParquet with Hive / AWS Athena:
ParquetDecodingException: totalValueCount '0' <= 0
Key: PARQUET-964
URL: https://issues.apache.org/jira/browse/PARQUET-964
Project: Parquet
Issue Type: Bug
Reporter: Costi Muraru
Hi folks!
We're working on adding support for ProtoParquet to work with Hive / AWS Athena
(Presto) \[1\]. The problem we've encountered appears whenever we declare a
repeated field (array) or a map in the protobuf schema and we then try to
convert it to parquet. The conversion works fine, but when we try to query the
data with Hive/Presto, we get some freaky errors.
We've noticed though that AvroToParquet works great, even when we declare such
fields (arrays, maps)!
Comparing the parquet schema generated by avro vs protobuf, we've noticed a few
differences.
Take the simple schema below (protobuf):
{code}
message ListOfList {
string top_field = 1;
repeated MyInnerMessage first_array = 2;
}
message MyInnerMessage {
int32 inner_field = 1;
repeated int32 second_array = 2;
}
{code}
After using ProtoParquetWriter, the resulting parquet schema is the following:
{code}
message TestProtobuf.ListOfList {
optional binary top_field (UTF8);
repeated group first_array {
optional int32 inner_field;
repeated int32 second_array;
}
}
{code}
When we try to query this data, we get parsing errors from Hive/Athena. The
parsing errors are related to the array/map fields.
However, if we create a similar avro schema, the parquet result of the
AvroParquetWriter is the following:
{code}
message TestProtobuf.ListOfList {
optional binary top_field (UTF8);
required group first_array (LIST) {
repeated group array {
optional int32 inner_field;
required group second_array (LIST) {
repeated int32 array;
}
}
}
}
{code}
This works beautifully wit Hive/Athena. Too bad our systems are stuck with
protobuf :-) .
You can see the additional wrappers which are missing from protobuf: {{required
group first_array (LIST)}}.
Our goal is to make the ProtoParquetWriter generate a parquet schema similar to
what Avro is doing. We basically want to add these wrappers around lists/maps.
Everything seemed to work great, until we've bumped into an issue. We tuned
ProtoParquetWriter to generate the same parquet schema as AvroParquetWriter.
However, one difference between protobuf and avro is that in protobuf we can
have a bunch of Optional fields. When combining an optional field with a list,
we got an error:
{noformat}
parquet-tools cat /tmp/test23.parquet
org.apache.parquet.io.ParquetDecodingException: Can not read value at 0 in
block -1 in file file:/tmp/test23.parquet
at
org.apache.parquet.hadoop.InternalParquetRecordReader.nextKeyValue(InternalParquetRecordReader.java:223)
at org.apache.parquet.hadoop.ParquetReader.read(ParquetReader.java:122)
at org.apache.parquet.hadoop.ParquetReader.read(ParquetReader.java:126)
at
org.apache.parquet.tools.command.CatCommand.execute(CatCommand.java:79)
at org.apache.parquet.proto.tools.Main.main(Main.java:214)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: org.apache.parquet.io.ParquetDecodingException: totalValueCount '0'
<= 0
at
org.apache.parquet.column.impl.ColumnReaderImpl.<init>(ColumnReaderImpl.java:349)
at
org.apache.parquet.column.impl.ColumnReadStoreImpl.newMemColumnReader(ColumnReadStoreImpl.java:82)
at
org.apache.parquet.column.impl.ColumnReadStoreImpl.getColumnReader(ColumnReadStoreImpl.java:77)
at
org.apache.parquet.io.RecordReaderImplementation.<init>(RecordReaderImplementation.java:272)
at
org.apache.parquet.io.MessageColumnIO$1.visit(MessageColumnIO.java:145)
at
org.apache.parquet.io.MessageColumnIO$1.visit(MessageColumnIO.java:107)
at
org.apache.parquet.filter2.compat.FilterCompat$NoOpFilter.accept(FilterCompat.java:155)
at
org.apache.parquet.io.MessageColumnIO.getRecordReader(MessageColumnIO.java:107)
at
org.apache.parquet.hadoop.InternalParquetRecordReader.checkRead(InternalParquetRecordReader.java:136)
at
org.apache.parquet.hadoop.InternalParquetRecordReader.nextKeyValue(InternalParquetRecordReader.java:194)
... 9 more
org.apache.parquet.io.ParquetDecodingException: Can not read value at 0 in
block -1 in file file:/tmp/test23.parquet
Process finished with exit code 1
{noformat}
Basically this errors occurs whenever the {{first_array.inner_field}} is not
populated, but {{first_array.second_array}} is.
I'm attaching the code used to generate the parquet files.
Going through the code, I've noticed that the errors stops and everything seems
work once I change this condition in ColumnReaderImpl:
From:
{code}
if (totalValueCount <= 0) {
throw new ParquetDecodingException("totalValueCount '" + totalValueCount
+ "' <= 0");
}
{code}
To:
{code}
if (totalValueCount < 0) {
throw new ParquetDecodingException("totalValueCount '" + totalValueCount
+ "' < 0");
}
{code}
https://github.com/apache/parquet-mr/blob/master/parquet-column/src/main/java/org/apache/parquet/column/impl/ColumnReaderImpl.java#L355
--->
{noformat}
[main] INFO org.apache.parquet.hadoop.InternalParquetRecordReader -
RecordReader initialized will read a total of 10 records.
[main] INFO org.apache.parquet.hadoop.InternalParquetRecordReader - at row 0.
reading next block
[main] INFO org.apache.parquet.hadoop.InternalParquetRecordReader - block read
in memory in 27 ms. row count = 10
top_field = top_field
first_array:
.array:
..second_array:
...array = 20
top_field = top_field
first_array:
.array:
..second_array:
...array = 20
{noformat}
I am wondering what are your thoughts on this? Should we change this condition
to {{if (totalValueCount < 0)}}?
Any feedback is gladly appreciated!
Thanks,
Costi
\[1\] https://aws.amazon.com/athena/
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