zeroshade commented on code in PR #38367:
URL: https://github.com/apache/arrow/pull/38367#discussion_r1376434496


##########
go/parquet/internal/encoding/boolean_decoder.go:
##########
@@ -109,3 +114,76 @@ func (dec *PlainBooleanDecoder) DecodeSpaced(out []bool, 
nullCount int, validBit
        }
        return dec.Decode(out)
 }
+
+type RleBooleanDecoder struct {
+       decoder
+
+       rleDec *utils.RleDecoder
+}
+
+func (RleBooleanDecoder) Type() parquet.Type {
+       return parquet.Types.Boolean
+}
+
+func (dec *RleBooleanDecoder) SetData(nvals int, data []byte) error {
+       dec.nvals = nvals
+
+       if len(data) < 4 {
+               return fmt.Errorf("invalid length - %d (corrupt data page?)", 
len(data))
+       }
+
+       // load the first 4 bytes in little-endian which indicates the length
+       nbytes := binary.LittleEndian.Uint32(data[:4])
+       if nbytes > uint32(len(data)-4) {
+               return fmt.Errorf("received invalid number of bytes - %d 
(corrupt data page?)", nbytes)
+       }
+
+       dec.data = data[4:]
+       if dec.rleDec == nil {
+               dec.rleDec = utils.NewRleDecoder(bytes.NewReader(dec.data), 1)
+       } else {
+               dec.rleDec.Reset(bytes.NewReader(dec.data), 1)
+       }
+       return nil
+}
+
+func (dec *RleBooleanDecoder) Decode(out []bool) (int, error) {
+       max := shared_utils.MinInt(len(out), dec.nvals)
+
+       var (
+               buf [1024]uint64
+               n   = max
+       )
+
+       for n > 0 {
+               batch := shared_utils.MinInt(len(buf), n)
+               decoded := dec.rleDec.GetBatch(buf[:batch])
+               if decoded != batch {
+                       return max - n, io.ErrUnexpectedEOF

Review Comment:
   Hmm, you have a point though I think that would be a greater issue to think 
about attempting to fix. 
   
   For DataPageV2Header it contains the number of nulls so we can easily handle 
changing `dec.nvals` to the correct number, but for DataPageV1 you have a point 
that *technically* this might be slightly off or is at least a bug waiting to 
happen that should be addressed.



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