emkornfield commented on a change in pull request #10537:
URL: https://github.com/apache/arrow/pull/10537#discussion_r652322182
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File path: cpp/src/parquet/file_reader.cc
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@@ -74,6 +74,41 @@ std::shared_ptr<ColumnReader> RowGroupReader::Column(int i) {
const_cast<ReaderProperties*>(contents_->properties())->memory_pool());
}
+std::shared_ptr<ColumnReader> RowGroupReader::ColumnWithExposeEncoding(
+ int i, ExposedEncodingType encoding_to_expose) {
+ auto encoding_stats = metadata()->ColumnChunk(i)->encoding_stats();
+ auto reader = Column(i);
+
+ if (encoding_stats.empty()) {
+ return reader;
+ }
+
+ if (encoding_to_expose == ExposedEncodingType::DICTIONARY) {
+ // The 1st page should be the dictionary page.
+ if (encoding_stats[0].page_type != PageType::DICTIONARY_PAGE ||
+ (encoding_stats[0].encoding != Encoding::PLAIN &&
+ encoding_stats[0].encoding != Encoding::PLAIN_DICTIONARY)) {
+ return reader;
+ }
+ // The following pages should be dictionary encoded data pages.
+ for (size_t idx = 1; idx < encoding_stats.size(); ++idx) {
+ if ((encoding_stats[idx].encoding != Encoding::RLE_DICTIONARY &&
+ encoding_stats[idx].encoding != Encoding::PLAIN_DICTIONARY) ||
+ (encoding_stats[idx].page_type != PageType::DATA_PAGE &&
+ encoding_stats[idx].page_type != PageType::DATA_PAGE_V2)) {
+ return reader;
+ }
+ }
+ } else {
Review comment:
instead of this else it is probably cleaner to add a guard.
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