update docstring

Author: wgtmac

cpp/src/parquet/properties.h

@@ -525,7 +525,8 @@ class PARQUET_EXPORT WriterProperties {
     /// Enable writing page index in general for all columns. Default disabled.
     ///
     /// Page index contains statistics for data pages and can be used to skip pages
-    /// when scanning data in ordered and unordered columns.
+    /// when scanning data in ordered and unordered columns. Note that it does not
+    /// write statistics to the page header once page index is enabled.
     ///
     /// Please check the link below for more details:
     /// https://github.com/apache/parquet-format/blob/master/PageIndex.md
@@ -541,6 +542,8 @@ class PARQUET_EXPORT WriterProperties {
     }
 
     /// Enable writing page index for column specified by `path`. Default disabled.
+    /// Note that it does not write statistics to the page header once page index is
+    /// enabled.
     Builder* enable_write_page_index(const std::string& path) {
       page_index_enabled_[path] = true;
       return this;

docs/source/cpp/parquet.rst

@@ -304,6 +304,8 @@ Statistics are enabled by default for all columns. You can disable statistics fo
 all columns or specific columns using ``disable_statistics`` on the builder.
 There is a ``max_statistics_size`` which limits the maximum number of bytes that
 may be used for min and max values, useful for types like strings or binary blobs.
+If a column has enabled page index using ``enable_write_page_index``, then it does
+not write statistics to the page header because it is duplicated in the ColumnIndex.
 
 There are also Arrow-specific settings that can be configured with
 :class:`parquet::ArrowWriterProperties`:
@@ -573,20 +575,14 @@ Miscellaneous
 +--------------------------+----------+----------+---------+
 | Feature                  | Reading  | Writing  | Notes   |
 +==========================+==========+==========+=========+
-| Column Index             | ✓        |          | \(1)    |
+| Column Index             | ✓        | ✓        |         |
 +--------------------------+----------+----------+---------+
-| Offset Index             | ✓        |          | \(1)    |
+| Offset Index             | ✓        | ✓        |         |
 +--------------------------+----------+----------+---------+
-| Bloom Filter             | ✓        | ✓        | \(2)    |
+| Bloom Filter             | ✓        | ✓        | \(1)    |
 +--------------------------+----------+----------+---------+
-| CRC checksums            | ✓        | ✓        | \(3)    |
+| CRC checksums            | ✓        | ✓        |         |
 +--------------------------+----------+----------+---------+
 
-* \(1) Access to the Column and Offset Index structures is provided, but
-  data read APIs do not currently make any use of them.
-
-* \(2) APIs are provided for creating, serializing and deserializing Bloom
+* \(1) APIs are provided for creating, serializing and deserializing Bloom
   Filters, but they are not integrated into data read APIs.
-
-* \(3) For now, only the checksums of V1 Data Pages and Dictionary Pages
-  are computed.