From 77155a13770fd5b7407de12a27aa6cddc19ad480 Mon Sep 17 00:00:00 2001
From: Shiv Bhatia <shivbhatia10@gmail.com>
Date: Sun, 28 Sep 2025 03:48:50 +0100
Subject: [PATCH 1/2] Extend datatype semantic equality check to include
 timestamps (#17777)

* Extend datatype semantic equality to include timestamps

* test

* Respond to comments

* cargo fmt

---------

Co-authored-by: Shiv Bhatia <sbhatia@palantir.com>
---
 datafusion/common/src/dfschema.rs | 36 ++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/datafusion/common/src/dfschema.rs b/datafusion/common/src/dfschema.rs
index f9e3b2cee40d..1bf64f0db9b4 100644
--- a/datafusion/common/src/dfschema.rs
+++ b/datafusion/common/src/dfschema.rs
@@ -747,7 +747,8 @@ impl DFSchema {
     }
 
     /// Returns true of two [`DataType`]s are semantically equal (same
-    /// name and type), ignoring both metadata and nullability, and decimal precision/scale.
+    /// name and type), ignoring both metadata and nullability, decimal precision/scale,
+    /// and timezone time units/timezones.
     ///
     /// request to upstream: <https://github.com/apache/arrow-rs/issues/3199>
     pub fn datatype_is_semantically_equal(dt1: &DataType, dt2: &DataType) -> bool {
@@ -806,6 +807,10 @@ impl DFSchema {
                 DataType::Decimal256(_l_precision, _l_scale),
                 DataType::Decimal256(_r_precision, _r_scale),
             ) => true,
+            (
+                DataType::Timestamp(_l_time_unit, _l_timezone),
+                DataType::Timestamp(_r_time_unit, _r_timezone),
+            ) => true,
             _ => dt1 == dt2,
         }
     }
@@ -1596,6 +1601,35 @@ mod tests {
             &DataType::Int16
         ));
 
+        // Succeeds if decimal precision and scale are different
+        assert!(DFSchema::datatype_is_semantically_equal(
+            &DataType::Decimal32(1, 2),
+            &DataType::Decimal32(2, 1),
+        ));
+
+        assert!(DFSchema::datatype_is_semantically_equal(
+            &DataType::Decimal64(1, 2),
+            &DataType::Decimal64(2, 1),
+        ));
+
+        assert!(DFSchema::datatype_is_semantically_equal(
+            &DataType::Decimal128(1, 2),
+            &DataType::Decimal128(2, 1),
+        ));
+
+        assert!(DFSchema::datatype_is_semantically_equal(
+            &DataType::Decimal256(1, 2),
+            &DataType::Decimal256(2, 1),
+        ));
+
+        // Any two timestamp types should match
+        assert!(DFSchema::datatype_is_semantically_equal(
+            &DataType::Timestamp(
+                arrow::datatypes::TimeUnit::Microsecond,
+                Some("UTC".into())
+            ),
+            &DataType::Timestamp(arrow::datatypes::TimeUnit::Millisecond, None),
+        ));
         // Test lists
 
         // Succeeds if both have the same element type, disregards names and nullability

From c431fec11a4b4d7e729db49affc36cc64da7ac75 Mon Sep 17 00:00:00 2001
From: Andrew Lamb <andrew@nerdnetworks.org>
Date: Sun, 19 Oct 2025 16:45:41 -0400
Subject: [PATCH 2/2] remove incorectly backported test

---
 datafusion/common/src/dfschema.rs | 21 ---------------------
 1 file changed, 21 deletions(-)

diff --git a/datafusion/common/src/dfschema.rs b/datafusion/common/src/dfschema.rs
index 1bf64f0db9b4..8cb6678e0068 100644
--- a/datafusion/common/src/dfschema.rs
+++ b/datafusion/common/src/dfschema.rs
@@ -1601,27 +1601,6 @@ mod tests {
             &DataType::Int16
         ));
 
-        // Succeeds if decimal precision and scale are different
-        assert!(DFSchema::datatype_is_semantically_equal(
-            &DataType::Decimal32(1, 2),
-            &DataType::Decimal32(2, 1),
-        ));
-
-        assert!(DFSchema::datatype_is_semantically_equal(
-            &DataType::Decimal64(1, 2),
-            &DataType::Decimal64(2, 1),
-        ));
-
-        assert!(DFSchema::datatype_is_semantically_equal(
-            &DataType::Decimal128(1, 2),
-            &DataType::Decimal128(2, 1),
-        ));
-
-        assert!(DFSchema::datatype_is_semantically_equal(
-            &DataType::Decimal256(1, 2),
-            &DataType::Decimal256(2, 1),
-        ));
-
         // Any two timestamp types should match
         assert!(DFSchema::datatype_is_semantically_equal(
             &DataType::Timestamp(