From abc62576b9386e730174f598260ed0aa5b43a1c0 Mon Sep 17 00:00:00 2001
From: Ritchie Vink <ritchie46@gmail.com>
Date: Sat, 8 Jan 2022 21:54:43 +0100
Subject: [PATCH] Parquet: add as_any and null_count to dyn Statistics (#743)

---
 src/io/parquet/read/statistics/binary.rs    | 17 +++++++++++++++++
 src/io/parquet/read/statistics/boolean.rs   |  9 +++++++++
 src/io/parquet/read/statistics/fixlen.rs    |  9 +++++++++
 src/io/parquet/read/statistics/mod.rs       |  7 +++++++
 src/io/parquet/read/statistics/primitive.rs |  9 +++++++++
 5 files changed, 51 insertions(+)

diff --git a/src/io/parquet/read/statistics/binary.rs b/src/io/parquet/read/statistics/binary.rs
index db0e40276ab..e8f272cc24a 100644
--- a/src/io/parquet/read/statistics/binary.rs
+++ b/src/io/parquet/read/statistics/binary.rs
@@ -1,3 +1,4 @@
+use std::any::Any;
 use std::convert::TryFrom;
 
 use crate::datatypes::DataType;
@@ -20,6 +21,14 @@ impl Statistics for BinaryStatistics {
     fn data_type(&self) -> &DataType {
         &DataType::Binary
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn null_count(&self) -> Option<i64> {
+        self.null_count
+    }
 }
 
 impl From<&ParquetByteArrayStatistics> for BinaryStatistics {
@@ -45,6 +54,14 @@ impl Statistics for Utf8Statistics {
     fn data_type(&self) -> &DataType {
         &DataType::Utf8
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn null_count(&self) -> Option<i64> {
+        self.null_count
+    }
 }
 
 impl TryFrom<&ParquetByteArrayStatistics> for Utf8Statistics {
diff --git a/src/io/parquet/read/statistics/boolean.rs b/src/io/parquet/read/statistics/boolean.rs
index 946591c8c4a..4817dbde3b3 100644
--- a/src/io/parquet/read/statistics/boolean.rs
+++ b/src/io/parquet/read/statistics/boolean.rs
@@ -1,5 +1,6 @@
 use crate::datatypes::DataType;
 use parquet2::statistics::BooleanStatistics as ParquetBooleanStatistics;
+use std::any::Any;
 
 use super::Statistics;
 
@@ -15,6 +16,14 @@ impl Statistics for BooleanStatistics {
     fn data_type(&self) -> &DataType {
         &DataType::Boolean
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn null_count(&self) -> Option<i64> {
+        self.null_count
+    }
 }
 
 impl From<&ParquetBooleanStatistics> for BooleanStatistics {
diff --git a/src/io/parquet/read/statistics/fixlen.rs b/src/io/parquet/read/statistics/fixlen.rs
index 6bd3e960021..867c7e84e09 100644
--- a/src/io/parquet/read/statistics/fixlen.rs
+++ b/src/io/parquet/read/statistics/fixlen.rs
@@ -1,3 +1,4 @@
+use std::any::Any;
 use std::convert::{TryFrom, TryInto};
 
 use super::super::schema;
@@ -27,6 +28,14 @@ impl Statistics for FixedLenStatistics {
     fn data_type(&self) -> &DataType {
         &self.data_type
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn null_count(&self) -> Option<i64> {
+        self.null_count
+    }
 }
 
 impl From<&ParquetFixedLenStatistics> for FixedLenStatistics {
diff --git a/src/io/parquet/read/statistics/mod.rs b/src/io/parquet/read/statistics/mod.rs
index 2b3d97a17f3..0e720097443 100644
--- a/src/io/parquet/read/statistics/mod.rs
+++ b/src/io/parquet/read/statistics/mod.rs
@@ -4,6 +4,7 @@ use crate::error::ArrowError;
 use parquet2::schema::types::PhysicalType;
 use parquet2::statistics::PrimitiveStatistics as ParquetPrimitiveStatistics;
 use parquet2::statistics::Statistics as ParquetStatistics;
+use std::any::Any;
 
 use crate::error::Result;
 
@@ -20,6 +21,12 @@ pub use fixlen::*;
 pub trait Statistics: std::fmt::Debug {
     /// returns the [`DataType`] of the statistics.
     fn data_type(&self) -> &DataType;
+
+    /// Returns `dyn Any` can used to downcast to a physical type.
+    fn as_any(&self) -> &dyn Any;
+
+    /// Return the null count statistic
+    fn null_count(&self) -> Option<i64>;
 }
 
 impl PartialEq for &dyn Statistics {
diff --git a/src/io/parquet/read/statistics/primitive.rs b/src/io/parquet/read/statistics/primitive.rs
index f807754ea0d..14c90901bc1 100644
--- a/src/io/parquet/read/statistics/primitive.rs
+++ b/src/io/parquet/read/statistics/primitive.rs
@@ -2,6 +2,7 @@ use crate::{datatypes::DataType, types::NativeType};
 use parquet2::schema::types::ParquetType;
 use parquet2::statistics::PrimitiveStatistics as ParquetPrimitiveStatistics;
 use parquet2::types::NativeType as ParquetNativeType;
+use std::any::Any;
 
 use super::super::schema;
 use super::Statistics;
@@ -20,6 +21,14 @@ impl<T: NativeType> Statistics for PrimitiveStatistics<T> {
     fn data_type(&self) -> &DataType {
         &self.data_type
     }
+
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn null_count(&self) -> Option<i64> {
+        self.null_count
+    }
 }
 
 impl<T, R> From<(&ParquetPrimitiveStatistics<R>, DataType)> for PrimitiveStatistics<T>