From 59195eb90a992474e90331951cd53e0c56fcf4f9 Mon Sep 17 00:00:00 2001
From: Raushan Prabhakar <ros@Raushans-MacBook-Air.local>
Date: Sun, 17 May 2026 01:32:58 +0530
Subject: [PATCH] fixing array length for empty array

---
 datafusion/functions-nested/src/length.rs                | 4 +++-
 .../sqllogictest/test_files/array/array_length.slt       | 9 +++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/datafusion/functions-nested/src/length.rs b/datafusion/functions-nested/src/length.rs
index 9579c3c9cd658..b1550af7cd686 100644
--- a/datafusion/functions-nested/src/length.rs
+++ b/datafusion/functions-nested/src/length.rs
@@ -188,7 +188,9 @@ fn compute_array_length(
 
     loop {
         if current_dimension == dimension {
-            return Ok(Some(value.len() as u64));
+            // PostgreSQL: array_length(anyarray, dimension) returns NULL when that
+            // dimension is empty (`array_length('{}'::int[], 1)`), not zero.
+            return Ok((!value.is_empty()).then(|| value.len() as u64));
         }
 
         match value.data_type() {
diff --git a/datafusion/sqllogictest/test_files/array/array_length.slt b/datafusion/sqllogictest/test_files/array/array_length.slt
index 1bb5382339854..ba784b29404fc 100644
--- a/datafusion/sqllogictest/test_files/array/array_length.slt
+++ b/datafusion/sqllogictest/test_files/array/array_length.slt
@@ -65,11 +65,16 @@ select array_length(arrow_cast(array_repeat(array_repeat(array_repeat(3, 5), 2),
 ----
 3 2
 
-# array_length scalar function #5
+# array_length scalar function #5 empty array dimension (PostgreSQL-compatible)
 query III
 select array_length(make_array()), array_length(make_array(), 1), array_length(make_array(), 2)
 ----
-0 0 NULL
+NULL NULL NULL
+
+query I
+SELECT array_length(ARRAY[]::INT[], 1)
+----
+NULL
 
 # array_length scalar function #6 nested array
 query III