From 58469d910d5f1945f030594ace9e7e8152223389 Mon Sep 17 00:00:00 2001
From: Adrian Garcia Badaracco <1755071+adriangb@users.noreply.github.com>
Date: Fri, 24 Oct 2025 17:04:55 -0500
Subject: [PATCH 1/2] fix null count stats computation

---
 datafusion/datasource-parquet/src/metadata.rs | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/datafusion/datasource-parquet/src/metadata.rs b/datafusion/datasource-parquet/src/metadata.rs
index 4de68793ce02..c8ee4d3b9f57 100644
--- a/datafusion/datasource-parquet/src/metadata.rs
+++ b/datafusion/datasource-parquet/src/metadata.rs
@@ -299,7 +299,6 @@ impl<'a> DFParquetMetadata<'a> {
                             summarize_min_max_null_counts(
                                 &mut accumulators,
                                 idx,
-                                num_rows,
                                 &stats_converter,
                                 row_groups_metadata,
                             )
@@ -417,7 +416,6 @@ struct StatisticsAccumulators<'a> {
 fn summarize_min_max_null_counts(
     accumulators: &mut StatisticsAccumulators,
     arrow_schema_index: usize,
-    num_rows: usize,
     stats_converter: &StatisticsConverter,
     row_groups_metadata: &[RowGroupMetaData],
 ) -> Result<()> {
@@ -449,11 +447,14 @@ fn summarize_min_max_null_counts(
         );
     }
 
-    accumulators.null_counts_array[arrow_schema_index] =
-        Precision::Exact(match sum(&null_counts) {
-            Some(null_count) => null_count as usize,
-            None => num_rows,
-        });
+    accumulators.null_counts_array[arrow_schema_index] = match sum(&null_counts) {
+        Some(null_count) => Precision::Exact(null_count as usize),
+        None => match null_counts.len() {
+            // If sum() returned None we either have no rows or all values are null
+            0 => Precision::Exact(0),
+            _ => Precision::Absent,
+        },
+    };
 
     Ok(())
 }

From 75471c0532324e39708100934a368a2c47c8aed2 Mon Sep 17 00:00:00 2001
From: Adrian Garcia Badaracco <1755071+adriangb@users.noreply.github.com>
Date: Fri, 24 Oct 2025 17:39:54 -0500
Subject: [PATCH 2/2] add test

---
 .../sqllogictest/test_files/parquet.slt       | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/datafusion/sqllogictest/test_files/parquet.slt b/datafusion/sqllogictest/test_files/parquet.slt
index e722005bf0f0..11942108ab2b 100644
--- a/datafusion/sqllogictest/test_files/parquet.slt
+++ b/datafusion/sqllogictest/test_files/parquet.slt
@@ -862,3 +862,30 @@ select part, k, v from t order by k
 
 statement ok
 DROP TABLE t;
+
+# Regression test for files with stats on some columns and not others
+# See https://github.com/apache/datafusion/pull/18276
+
+query I
+COPY (SELECT 1::int AS a, 2::int as b)
+TO 'test_files/scratch/parquet/mixed_stats.parquet'
+STORED AS PARQUET OPTIONS (
+  'STATISTICS_ENABLED::b' 'none'
+);
+----
+1
+
+statement ok
+CREATE EXTERNAL TABLE t
+STORED AS PARQUET
+LOCATION 'test_files/scratch/parquet/mixed_stats.parquet';
+
+query I
+SELECT b
+FROM t
+WHERE b = 2;
+----
+2
+
+statement ok
+DROP TABLE t;