From da1b51a4969d17c0c1bd23e330cde1864cb9c51e Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Fri, 17 Jan 2020 22:57:03 +0300
Subject: [PATCH] Added function bitCount #8702

---
 dbms/src/Functions/bitCount.cpp               | 42 +++++++++++++++++++
 .../Functions/registerFunctionsArithmetic.cpp |  2 +
 .../0_stateless/01066_bit_count.reference     | 21 ++++++++++
 .../queries/0_stateless/01066_bit_count.sql   | 13 ++++++
 4 files changed, 78 insertions(+)
 create mode 100644 dbms/src/Functions/bitCount.cpp
 create mode 100644 dbms/tests/queries/0_stateless/01066_bit_count.reference
 create mode 100644 dbms/tests/queries/0_stateless/01066_bit_count.sql

diff --git a/dbms/src/Functions/bitCount.cpp b/dbms/src/Functions/bitCount.cpp
new file mode 100644
index 00000000000..13225031a8e
--- /dev/null
+++ b/dbms/src/Functions/bitCount.cpp
@@ -0,0 +1,42 @@
+#include <ext/bit_cast.h>
+#include <Functions/FunctionFactory.h>
+#include <Functions/FunctionUnaryArithmetic.h>
+
+
+namespace DB
+{
+
+template <typename A>
+struct BitCountImpl
+{
+    using ResultType = UInt8;
+
+    static inline ResultType apply(A a)
+    {
+        return __builtin_popcountll(ext::bit_cast<unsigned long long>(a));
+    }
+
+#if USE_EMBEDDED_COMPILER
+    static constexpr bool compilable = false;
+#endif
+};
+
+struct NameBitCount { static constexpr auto name = "bitCount"; };
+using FunctionBitCount = FunctionUnaryArithmetic<BitCountImpl, NameBitCount, true>;
+
+/// The function has no ranges of monotonicity.
+template <> struct FunctionUnaryArithmeticMonotonicity<NameBitCount>
+{
+    static bool has() { return false; }
+    static IFunction::Monotonicity get(const Field &, const Field &)
+    {
+        return {};
+    }
+};
+
+void registerFunctionBitCount(FunctionFactory & factory)
+{
+    factory.registerFunction<FunctionBitCount>();
+}
+
+}
diff --git a/dbms/src/Functions/registerFunctionsArithmetic.cpp b/dbms/src/Functions/registerFunctionsArithmetic.cpp
index eb68fc32fa1..88350b4fac7 100644
--- a/dbms/src/Functions/registerFunctionsArithmetic.cpp
+++ b/dbms/src/Functions/registerFunctionsArithmetic.cpp
@@ -20,6 +20,7 @@ void registerFunctionBitShiftLeft(FunctionFactory & factory);
 void registerFunctionBitShiftRight(FunctionFactory & factory);
 void registerFunctionBitRotateLeft(FunctionFactory & factory);
 void registerFunctionBitRotateRight(FunctionFactory & factory);
+void registerFunctionBitCount(FunctionFactory & factory);
 void registerFunctionLeast(FunctionFactory & factory);
 void registerFunctionGreatest(FunctionFactory & factory);
 void registerFunctionBitTest(FunctionFactory & factory);
@@ -58,6 +59,7 @@ void registerFunctionsArithmetic(FunctionFactory & factory)
     registerFunctionBitShiftRight(factory);
     registerFunctionBitRotateLeft(factory);
     registerFunctionBitRotateRight(factory);
+    registerFunctionBitCount(factory);
     registerFunctionLeast(factory);
     registerFunctionGreatest(factory);
     registerFunctionBitTest(factory);
diff --git a/dbms/tests/queries/0_stateless/01066_bit_count.reference b/dbms/tests/queries/0_stateless/01066_bit_count.reference
new file mode 100644
index 00000000000..4a3b084b4a2
--- /dev/null
+++ b/dbms/tests/queries/0_stateless/01066_bit_count.reference
@@ -0,0 +1,21 @@
+0
+1
+1
+2
+1
+2
+2
+3
+1
+2
+4
+0
+1
+8
+64
+32
+16
+8
+1	10	000000000000F03F
+-1	11	000000000000F0BF
+inf	11	000000000000F07F
diff --git a/dbms/tests/queries/0_stateless/01066_bit_count.sql b/dbms/tests/queries/0_stateless/01066_bit_count.sql
new file mode 100644
index 00000000000..d50b2657542
--- /dev/null
+++ b/dbms/tests/queries/0_stateless/01066_bit_count.sql
@@ -0,0 +1,13 @@
+SELECT bitCount(number) FROM numbers(10);
+SELECT avg(bitCount(number)) FROM numbers(256);
+
+SELECT bitCount(0);
+SELECT bitCount(1);
+SELECT bitCount(-1);
+
+SELECT bitCount(toInt64(-1));
+SELECT bitCount(toInt32(-1));
+SELECT bitCount(toInt16(-1));
+SELECT bitCount(toInt8(-1));
+
+SELECT x, bitCount(x), hex(reinterpretAsString(x)) FROM VALUES ('x Float64', (1), (-1), (inf));