PARQUET-2473: Clarify records can not be split across v2 pages or Pag…

…eIndex (#244)


Co-authored-by: Ed Seidl <[email protected]>

src/main/thrift/parquet.thrift

@@ -578,7 +578,13 @@ enum BoundaryOrder {
 
 /** Data page header */
 struct DataPageHeader {
-  /** Number of values, including NULLs, in this data page. **/
+  /**
+   * Number of values, including NULLs, in this data page.
+   *
+   * If a OffsetIndex is present, a page must begin at a record
+   * boundary (repetition_level = 0). Otherwise, pages may begin
+   * within a record (repetition_level > 0).
+   **/
   1: required i32 num_values
 
   /** Encoding used for this data page **/
@@ -625,7 +631,11 @@ struct DataPageHeaderV2 {
   /** Number of NULL values, in this data page.
       Number of non-null = num_values - num_nulls which is also the number of values in the data section **/
   2: required i32 num_nulls
-  /** Number of rows in this data page. which means pages change on record boundaries (r = 0) **/
+  /**
+   * Number of rows in this data page. Every page must begin at a
+   * record boundary (repetition_level = 0): records must **not** be
+   * split across page boundaries when using V2 data pages.
+   **/
   3: required i32 num_rows
   /** Encoding used for data in this page **/
   4: required Encoding encoding
@@ -995,8 +1005,9 @@ struct PageLocation {
   2: required i32 compressed_page_size
 
   /**
-   * Index within the RowGroup of the first row of the page; this means pages
-   * change on record boundaries (r = 0).
+   * Index within the RowGroup of the first row of the page. When an
+   * OffsetIndex is present, pages must begin on record boundaries
+   * (repetition_level = 0).
    */
   3: required i64 first_row_index
 }
@@ -1190,4 +1201,3 @@ struct FileCryptoMetaData {
    *  and (possibly) columns **/
   2: optional binary key_metadata
 }
-