[GitHub] [arrow] wgtmac commented on a diff in pull request #14556: PARQUET-2211: [C++] Print ColumnMetaData.encoding_stats field

[GitBox <gi...@apache.org>]

wgtmac commented on code in PR #14556:
URL: https://github.com/apache/arrow/pull/14556#discussion_r1014841622


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cpp/src/parquet/printer.cc:
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@@ -39,6 +39,25 @@ namespace parquet {
 
 class ColumnReader;
 
+namespace {
+
+void PrintPageEncodingStats(std::ostream& stream,
+                            const std::vector<PageEncodingStats>& encoding_stats) {
+  for (size_t i = 0; i < encoding_stats.size(); ++i) {
+    const auto& encoding = encoding_stats.at(i);
+    stream << EncodingToString(encoding.encoding);
+    if (encoding.page_type == parquet::PageType::DICTIONARY_PAGE) {
+      // Explicitly tell if this encoding comes from a dictionary page
+      stream << "(DICT_PAGE)";

Review Comment:
   The main idea is to tell this encoding comes from the dictionary page. IIUC, both dictionary page and data page use PLAIN_DICTIONARY when dictionary encoding is applied in the Parquet 1.0. While in Parquet 2.0, dictionary page uses PLAIN and data page uses RLE_DICTIONARY. So it is difficult to tell where the PLAIN_DICTIONARY or PLAIN encoding comes from.  Please check this for detail:　https://github.com/apache/parquet-format/blob/master/Encodings.md#dictionary-encoding-plain_dictionary--2-and-rle_dictionary--8



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