alamb commented on code in PR #245:
URL: https://github.com/apache/parquet-format/pull/245#discussion_r1607433284
##########
PageIndex.md:
##########
@@ -17,11 +17,13 @@
- under the License.
-->
-# ColumnIndex Layout to Support Page Skipping
+# Parquet page index: Layout to Support Page Skipping
-This document describes the format for column index pages in the Parquet
-footer. These pages contain statistics for DataPages and can be used to skip
-pages when scanning data in ordered and unordered columns.
+In Parquet, a *page index* is optional metadata for a
+ColumnChunk, containing statistics for DataPages that can be used
+to skip those pages when scanning in ordered and unordered columns.
Review Comment:
I added
```diff
--- a/src/main/thrift/parquet.thrift
+++ b/src/main/thrift/parquet.thrift
@@ -1005,6 +1005,8 @@ struct PageLocation {
* Optional offsets for each data page in a ColumnChunk.
*
* Forms part of the page index, along with ColumnIndex.
+ *
+ * OffsetIndex may be present even if ColumnIndex is not.
*/
struct OffsetIndex {
/**
@@ -1026,6 +1028,8 @@ struct OffsetIndex {
*
* Forms part the page index, along with OffsetIndex.
*
+ * If this structure is present, OffsetIndex must also be present.
+ *
* For each field in this structure, <field>[i] refers to the page at
* OffsetIndex.page_locations[i]
*/
```
in 8d59c7d to try and clarify this
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