From 91fcff1fa1a5c5ee765dd6711daf14ddbe56fec5 Mon Sep 17 00:00:00 2001
From: Qiwei Huang <qiwei_huang@qq.com>
Date: Mon, 20 Oct 2025 22:44:40 +0800
Subject: [PATCH 1/3] Using MAX_DISCRIMINANT as the enum count

---
 parquet/src/basic.rs                 | 4 +++-
 parquet/src/column/reader/decoder.rs | 2 +-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/parquet/src/basic.rs b/parquet/src/basic.rs
index 7f50eada46de..ca82880b7547 100644
--- a/parquet/src/basic.rs
+++ b/parquet/src/basic.rs
@@ -678,6 +678,8 @@ enum Encoding {
   /// afterwards. Note that the use of this encoding with FIXED_LEN_BYTE_ARRAY(N) data may
   /// perform poorly for large values of N.
   BYTE_STREAM_SPLIT = 9;
+        SOME_ENCODING = 10;
+        SOME_OTHER11=11;
 }
 );
 
@@ -741,7 +743,7 @@ pub struct EncodingMask(i32);
 
 impl EncodingMask {
     /// Highest valued discriminant in the [`Encoding`] enum
-    const MAX_ENCODING: i32 = Encoding::BYTE_STREAM_SPLIT as i32;
+    const MAX_ENCODING: i32 = Encoding::MAX_DISCRIMINANT;
     /// A mask consisting of unused bit positions, used for validation. This includes the never
     /// used GROUP_VAR_INT encoding value of `1`.
     const ALLOWED_MASK: u32 =
diff --git a/parquet/src/column/reader/decoder.rs b/parquet/src/column/reader/decoder.rs
index 1d4e2f751181..e49906207577 100644
--- a/parquet/src/column/reader/decoder.rs
+++ b/parquet/src/column/reader/decoder.rs
@@ -138,7 +138,7 @@ pub trait ColumnValueDecoder {
 ///
 /// This replaces `HashMap` lookups with direct indexing to avoid hashing overhead in the
 /// hot decoding paths.
-const ENCODING_SLOTS: usize = Encoding::BYTE_STREAM_SPLIT as usize + 1;
+const ENCODING_SLOTS: usize = Encoding::MAX_DISCRIMINANT as usize + 1;
 
 /// An implementation of [`ColumnValueDecoder`] for `[T::T]`
 pub struct ColumnValueDecoderImpl<T: DataType> {

From 7986d7147535f5aab4e8524eb5ec2e9afef30654 Mon Sep 17 00:00:00 2001
From: Qiwei Huang <qiwei_huang@qq.com>
Date: Mon, 20 Oct 2025 22:47:34 +0800
Subject: [PATCH 2/3] Update the Macro

---
 parquet/src/parquet_macros.rs | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/parquet/src/parquet_macros.rs b/parquet/src/parquet_macros.rs
index eb8bc2b7f07a..d7f865de040e 100644
--- a/parquet/src/parquet_macros.rs
+++ b/parquet/src/parquet_macros.rs
@@ -79,6 +79,35 @@ macro_rules! thrift_enum {
                 Ok(field_id)
             }
         }
+
+        impl $identifier {
+            #[allow(deprecated)]
+            #[doc = "Returns a slice containing every variant of this enum."]
+            #[allow(dead_code)]
+            pub const VARIANTS: &'static [Self] = &[
+                $(Self::$field_name),*
+            ];
+
+            #[allow(deprecated)]
+            const fn max_discriminant_impl() -> i32 {
+                let values: &[i32] = &[$($field_value),*];
+                let mut max = values[0];
+                let mut idx = 1;
+                while idx < values.len() {
+                    let candidate = values[idx];
+                    if candidate > max {
+                        max = candidate;
+                    }
+                    idx += 1;
+                }
+                max
+            }
+
+            #[allow(deprecated)]
+            #[doc = "Returns the largest discriminant value defined for this enum."]
+            #[allow(dead_code)]
+            pub const MAX_DISCRIMINANT: i32 = Self::max_discriminant_impl();
+        }
     }
 }
 

From 8b39d268d1e4a6eb1dde3fe8d25a8181bc26f345 Mon Sep 17 00:00:00 2001
From: Qiwei Huang <qiwei_huang@qq.com>
Date: Mon, 20 Oct 2025 22:53:38 +0800
Subject: [PATCH 3/3] Remove the newly added encodings

---
 parquet/src/basic.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/parquet/src/basic.rs b/parquet/src/basic.rs
index ca82880b7547..def69f251581 100644
--- a/parquet/src/basic.rs
+++ b/parquet/src/basic.rs
@@ -678,8 +678,6 @@ enum Encoding {
   /// afterwards. Note that the use of this encoding with FIXED_LEN_BYTE_ARRAY(N) data may
   /// perform poorly for large values of N.
   BYTE_STREAM_SPLIT = 9;
-        SOME_ENCODING = 10;
-        SOME_OTHER11=11;
 }
 );