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https://issues.apache.org/jira/browse/PARQUET-152?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14596763#comment-14596763
]
Sergio Peña commented on PARQUET-152:
-------------------------------------
A fixed length byte array is still written as a BINARY, isn't it? If so, then I
think we should allow FIXED_LEN_BYTE_ARRAY to be decoded by
Encoding.DELTA_BYTE_ARRAY.
I tested something like this, and it worked:
{code}
DELTA_BYTE_ARRAY {
@Override
public ValuesReader getValuesReader(ColumnDescriptor descriptor,
ValuesType valuesType) {
if (descriptor.getType() != BINARY && descriptor.getType() !=
FIXED_LEN_BYTE_ARRAY) {
throw new ParquetDecodingException("Encoding DELTA_BYTE_ARRAY is only
supported for type BINARY and FIXED_LEN_BYTE_ARRAY");
}
return new DeltaByteArrayReader();
}
},
{code}
I'll create a PR, and run more tests to check this scenario.
> Encoding issue with fixed length byte arrays
> --------------------------------------------
>
> Key: PARQUET-152
> URL: https://issues.apache.org/jira/browse/PARQUET-152
> Project: Parquet
> Issue Type: Bug
> Reporter: Nezih Yigitbasi
> Priority: Minor
>
> While running some tests against the master branch I hit an encoding issue
> that seemed like a bug to me.
> I noticed that when writing a fixed length byte array and the array's size is
> > dictionaryPageSize (in my test it was 512), the encoding falls back to
> DELTA_BYTE_ARRAY as seen below:
> {noformat}
> Dec 17, 2014 3:41:10 PM INFO: parquet.hadoop.ColumnChunkPageWriteStore:
> written 12,125B for [flba_field] FIXED_LEN_BYTE_ARRAY: 5,000 values, 1,710B
> raw, 1,710B comp, 5 pages, encodings: [DELTA_BYTE_ARRAY]
> {noformat}
> But then read fails with the following exception:
> {noformat}
> Caused by: parquet.io.ParquetDecodingException: Encoding DELTA_BYTE_ARRAY is
> only supported for type BINARY
> at parquet.column.Encoding$7.getValuesReader(Encoding.java:193)
> at
> parquet.column.impl.ColumnReaderImpl.initDataReader(ColumnReaderImpl.java:534)
> at
> parquet.column.impl.ColumnReaderImpl.readPageV2(ColumnReaderImpl.java:574)
> at
> parquet.column.impl.ColumnReaderImpl.access$400(ColumnReaderImpl.java:54)
> at
> parquet.column.impl.ColumnReaderImpl$3.visit(ColumnReaderImpl.java:518)
> at
> parquet.column.impl.ColumnReaderImpl$3.visit(ColumnReaderImpl.java:510)
> at parquet.column.page.DataPageV2.accept(DataPageV2.java:123)
> at
> parquet.column.impl.ColumnReaderImpl.readPage(ColumnReaderImpl.java:510)
> at
> parquet.column.impl.ColumnReaderImpl.checkRead(ColumnReaderImpl.java:502)
> at
> parquet.column.impl.ColumnReaderImpl.consume(ColumnReaderImpl.java:604)
> at
> parquet.column.impl.ColumnReaderImpl.<init>(ColumnReaderImpl.java:348)
> at
> parquet.column.impl.ColumnReadStoreImpl.newMemColumnReader(ColumnReadStoreImpl.java:63)
> at
> parquet.column.impl.ColumnReadStoreImpl.getColumnReader(ColumnReadStoreImpl.java:58)
> at
> parquet.io.RecordReaderImplementation.<init>(RecordReaderImplementation.java:267)
> at parquet.io.MessageColumnIO$1.visit(MessageColumnIO.java:131)
> at parquet.io.MessageColumnIO$1.visit(MessageColumnIO.java:96)
> at
> parquet.filter2.compat.FilterCompat$NoOpFilter.accept(FilterCompat.java:136)
> at parquet.io.MessageColumnIO.getRecordReader(MessageColumnIO.java:96)
> at
> parquet.hadoop.InternalParquetRecordReader.checkRead(InternalParquetRecordReader.java:129)
> at
> parquet.hadoop.InternalParquetRecordReader.nextKeyValue(InternalParquetRecordReader.java:198)
> ... 16 more
> {noformat}
> When the array's size is < dictionaryPageSize, RLE_DICTIONARY encoding is
> used and read works fine:
> {noformat}
> Dec 17, 2014 3:39:50 PM INFO: parquet.hadoop.ColumnChunkPageWriteStore:
> written 50B for [flba_field] FIXED_LEN_BYTE_ARRAY: 5,000 values, 3B raw, 3B
> comp, 1 pages, encodings: [RLE_DICTIONARY, PLAIN], dic { 1 entries, 8B raw,
> 1B comp}
> {noformat}
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