[Go][Parquet] RLE problem with ''(blank)"

[allinux]

Describe the bug, including details regarding any error messages, version, and platform.

There is a bug where '' is loaded as \x00 when WithDictionaryDefault of parquet.WriterProperties is set to true when all data in the column is ''.
If processed as false, it is normally loaded as ''.
It seems to occur during RLE processing, but need to check.

sample_parquet.zip contains src.parquet and dest.parquet files, src.parquet is a file with '' and dest.parquet is a file reloaded with WithDictionaryDefault set to true.

• python code for check

In [1]: import pandas as pd
In [2]: src = pd.read_parquet('src.parquet')
In [3]: src
Out[3]: 
  reserved1
0          
1          
2          
3          
4          
5          

In [4]: src.iloc[0].to_dict()
Out[4]: {'reserved1': ''}

In [5]: dest = pd.read_parquet('dest.parquet')

In [6]: dest
Out[6]: 
  reserved1
0         
1         
2         
3         
4         
5         

In [7]: dest.iloc[0].to_dict()
Out[7]: {'reserved1': '\x00'}

sample_parquet.zip

Component(s)

Go

[zeroshade]

@allinux can you provide the code you are using to perform the writes?

[allinux]

@zeroshade
Thanks for the commet.
Please see sample code below.
(For the file src.parquet, please refer to the previously attached sample_parquet.zip.)

package main

import (
	"context"
	"os"

	"github.com/apache/arrow/go/v12/arrow/memory"
	"github.com/apache/arrow/go/v12/parquet"
	"github.com/apache/arrow/go/v12/parquet/file"
	"github.com/apache/arrow/go/v12/parquet/pqarrow"
)

func main() {
	mem := memory.NewCheckedAllocator(memory.DefaultAllocator)

	src, _ := file.OpenParquetFile("src.parquet", false, file.WithReadProps(parquet.NewReaderProperties(mem)))
	defer src.Close()

	schema := src.MetaData().Schema

	arrowRdr, _ := pqarrow.NewFileReader(src, pqarrow.ArrowReadProperties{}, mem)

	arrowSchema, _ := pqarrow.FromParquet(schema, &pqarrow.ArrowReadProperties{}, src.MetaData().KeyValueMetadata())

	props := parquet.NewWriterProperties(
		parquet.WithDictionaryDefault(true), // \x00
	)

	dest, _ := os.OpenFile("dest.parquet", os.O_CREATE|os.O_APPEND|os.O_RDWR|os.O_TRUNC, 0644)
	arrowWriter, _ := pqarrow.NewFileWriter(arrowSchema, dest, props, pqarrow.DefaultWriterProps())
	defer arrowWriter.Close()
	
	arrowWriter.NewRowGroup()
	for i, numRowGroups := 0, src.NumRowGroups(); i < numRowGroups; i++ {
		rowGroupReader := arrowRdr.RowGroup(i)
		for i, numColumns := 0, schema.NumColumns(); i < numColumns; i++ {
			datas, _ := rowGroupReader.Column(i).Read(context.Background())
			if datas.Len() > 0 {
				for _, ar := range datas.Chunks() {
					arrowWriter.WriteColumnData(ar)
				}
			}
			datas.Release()
		}
	}
}