From 1db35384d969f9239de84563927494148100c6d5 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@clickhouse.com>
Date: Mon, 15 May 2023 03:30:03 +0200
Subject: [PATCH] Support `bitCount` for big integers

---
 src/Functions/bitCount.cpp                    |  9 ++++++++-
 .../02736_bit_count_big_int.reference         | 13 +++++++++++++
 .../0_stateless/02736_bit_count_big_int.sql   | 19 +++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 tests/queries/0_stateless/02736_bit_count_big_int.reference
 create mode 100644 tests/queries/0_stateless/02736_bit_count_big_int.sql

diff --git a/src/Functions/bitCount.cpp b/src/Functions/bitCount.cpp
index 984f33b7001..566a11481be 100644
--- a/src/Functions/bitCount.cpp
+++ b/src/Functions/bitCount.cpp
@@ -9,7 +9,7 @@ namespace DB
 template <typename A>
 struct BitCountImpl
 {
-    using ResultType = UInt8;
+    using ResultType = std::conditional_t<(sizeof(A) * 8 >= 256), UInt16, UInt8>;
     static constexpr bool allow_string_or_fixed_string = true;
 
     static inline ResultType apply(A a)
@@ -17,6 +17,13 @@ struct BitCountImpl
         /// We count bits in the value representation in memory. For example, we support floats.
         /// We need to avoid sign-extension when converting signed numbers to larger type. So, uint8_t(-1) has 8 bits.
 
+        if constexpr (is_big_int_v<A>)
+        {
+            ResultType res = 0;
+            for (auto item : a.items)
+                res += __builtin_popcountll(item);
+            return res;
+        }
         if constexpr (std::is_same_v<A, UInt64> || std::is_same_v<A, Int64>)
             return __builtin_popcountll(a);
         if constexpr (std::is_same_v<A, UInt32> || std::is_same_v<A, Int32> || std::is_unsigned_v<A>)
diff --git a/tests/queries/0_stateless/02736_bit_count_big_int.reference b/tests/queries/0_stateless/02736_bit_count_big_int.reference
new file mode 100644
index 00000000000..a3a725ace69
--- /dev/null
+++ b/tests/queries/0_stateless/02736_bit_count_big_int.reference
@@ -0,0 +1,13 @@
+128
+256
+128
+256
+127
+255
+126
+255
+64
+UInt8
+UInt16
+UInt8
+UInt16
diff --git a/tests/queries/0_stateless/02736_bit_count_big_int.sql b/tests/queries/0_stateless/02736_bit_count_big_int.sql
new file mode 100644
index 00000000000..35a4a641606
--- /dev/null
+++ b/tests/queries/0_stateless/02736_bit_count_big_int.sql
@@ -0,0 +1,19 @@
+SELECT bitCount(CAST(-1 AS UInt128));
+SELECT bitCount(CAST(-1 AS UInt256));
+
+SELECT bitCount(CAST(-1 AS Int128));
+SELECT bitCount(CAST(-1 AS Int256));
+
+SELECT bitCount(CAST(-1 AS UInt128) - 1);
+SELECT bitCount(CAST(-1 AS UInt256) - 2);
+
+SELECT bitCount(CAST(-1 AS Int128) - 3);
+SELECT bitCount(CAST(-1 AS Int256) - 4);
+
+SELECT bitCount(CAST(0xFFFFFFFFFFFFFFFF AS Int256));
+
+SELECT toTypeName(bitCount(1::UInt128));
+SELECT toTypeName(bitCount(1::UInt256));
+
+SELECT toTypeName(bitCount(1::Int128));
+SELECT toTypeName(bitCount(1::Int256));