[Go] [Parquet] panic writing with DeltaBinaryPacked when column only has nulls

[mslevine]

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

The writer panics if DeltaBinaryPacked encoding is requested for a column that is all null. The following small change to an existing test case demonstrates the issue.

In case it matters, I'm using go version go1.20.4 darwin/amd64
I ran into this issue using arrow v12.0.0, but this changed testcase fails using the current head of main.

diff --git a/go/parquet/pqarrow/encode_arrow_test.go b/go/parquet/pqarrow/encode_arrow_test.go
index 877f584f2..0b83ec696 100644
--- a/go/parquet/pqarrow/encode_arrow_test.go
+++ b/go/parquet/pqarrow/encode_arrow_test.go
@@ -380,6 +380,8 @@ func TestWriteEmptyLists(t *testing.T) {
 
        props := parquet.NewWriterProperties(
                parquet.WithVersion(parquet.V1_0),
+               parquet.WithDictionaryDefault(false),
+               parquet.WithEncoding(parquet.Encodings.DeltaBinaryPacked),
        )
        arrprops := pqarrow.DefaultWriterProps()
        var buf bytes.Buffer

Component(s)

Go

[mslevine]

Reading more code, it seems possible the fix could be as simple as

diff --git a/go/parquet/internal/encoding/delta_bit_packing.go b/go/parquet/internal/encoding/delta_bit_packing.go
index 2ebe6ad98..d68044a07 100644
--- a/go/parquet/internal/encoding/delta_bit_packing.go
+++ b/go/parquet/internal/encoding/delta_bit_packing.go
@@ -458,7 +458,11 @@ func (enc *deltaBitPackEncoder) FlushValues() (Buffer, error) {
 
 // EstimatedDataEncodedSize returns the current amount of data actually flushed out and written
 func (enc *deltaBitPackEncoder) EstimatedDataEncodedSize() int64 {
-       return int64(enc.bitWriter.Written())
+       if enc.bitWriter != nil {
+               return int64(enc.bitWriter.Written())
+       } else {
+               return 0
+       }
 }
 
 // DeltaBitPackInt32Encoder is an encoder for the delta bitpacking encoding for int32 data.

(although I could easily believe that the correct response when nil is some constant other than 0)

[zeroshade]

@mslevine Thanks for filing this! Would you be interested in filing a PR with a new test case and your proposed fix? 😄 It should automatically tag me as a codeowner to review it if you do.

If you're not interested, I'll try to get to this when I have some time.

[abhimanyusinghgaur]

Hi @zeroshade @mapleFU, This issue isn't fixed by #37112. Can you please reopen it?

I have tested it locally on the current main and it fails. The proposed fix in this issue seems to work fine as a solution.

[zeroshade]

@abhimanyusinghgaur I can reopen this issue, after which can you file a PR with your proposed fix and add a unit test case that can replicate the crash without the fix?