jp0317 commented on code in PR #39153:
URL: https://github.com/apache/arrow/pull/39153#discussion_r1421218054
##########
cpp/src/parquet/column_reader.h:
##########
@@ -368,6 +368,11 @@ class PARQUET_EXPORT RecordReader {
virtual void DebugPrintState() = 0;
+ /// \brief Returns the dictionary owned by the current decoder. Throws an
+ /// exception if the current decoder is not for dictionary encoding.
+ /// \param[out] dictionary_length The number of dictionary entries.
+ virtual const uint8_t* ReadDictionary(int32_t* dictionary_length) = 0;
Review Comment:
i just make it consistent with the
[values()](https://github.com/apache/arrow/blob/main/cpp/src/parquet/column_reader.h#L384)
which uses `uint8_t*`. The caller should handle the conversion properly based
on the column type.
##########
cpp/src/parquet/column_reader.cc:
##########
@@ -1369,6 +1369,24 @@ class TypedRecordReader : public
TypedColumnReaderImpl<DType>,
return bytes_for_values;
}
+ const uint8_t* ReadDictionary(int32_t* dictionary_length) override {
+ if (this->current_decoder_ == nullptr && !this->HasNextInternal()) {
+ dictionary_length = 0;
+ return nullptr;
+ }
+ // Verify the current data page is dictionary encoded.
+ if (this->current_encoding_ != Encoding::RLE_DICTIONARY) {
Review Comment:
The current_encoding_ is [set as
rle_dictionary](https://github.com/apache/arrow/blob/main/cpp/src/parquet/column_reader.cc#L876)
if it's plain dictionary.
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