Add truncate(x,n) Presto function (#2892)

Summary:
Pull Request resolved: #2892

Adding truncate(x,n) Presto function

Differential Revision: D40516665

fbshipit-source-id: 295451a2a6de62bb6f4c126a326db564f8947066

velox/docs/functions/math.rst

@@ -134,6 +134,10 @@ Mathematical Functions
 
     Returns x rounded to integer by dropping digits after decimal point.
 
+.. function:: truncate(x, n) -> double
+
+    Returns x truncated to n decimal places. n can be negative to truncate n digits left of the decimal point.
+
 .. function:: width_bucket(x, bound1, bound2, n) -> bigint
 
     Returns the bin number of ``x`` in an equi-width histogram with the

velox/functions/prestosql/Arithmetic.h

@@ -486,10 +486,13 @@ struct EulerConstantFunction {
 
 template <typename T>
 struct TruncateFunction {
-  template <typename TInput>
-  FOLLY_ALWAYS_INLINE void call(TInput& result, TInput a) {
+  FOLLY_ALWAYS_INLINE void call(double& result, double a) {
     result = std::trunc(a);
   }
+
+  FOLLY_ALWAYS_INLINE void call(double& result, double a, int32_t n) {
+    result = truncate(a, n);
+  }
 };
 
 } // namespace

velox/functions/prestosql/ArithmeticImpl.h

@@ -19,6 +19,7 @@
 #include <cmath>
 #include <type_traits>
 #include "folly/CPortability.h"
+#include "velox/type/DoubleUtil.h"
 
 namespace facebook::velox::functions {
 
@@ -132,4 +133,31 @@ T ceil(const T& arg) {
   return results;
 }
 
+FOLLY_ALWAYS_INLINE double truncate(
+    const double& number,
+    const int32_t& decimals = 0) {
+  const bool dec_negative = (decimals < 0);
+  const auto log_10_size = DoubleUtil::kPowersOfTen.size(); // 309
+  if (dec_negative && decimals <= -log_10_size)
+    return 0.0;
+
+  const uint64_t abs_dec = dec_negative ? -decimals : decimals;
+  const double tmp = (abs_dec < log_10_size) ? DoubleUtil::kPowersOfTen[abs_dec]
+                                             : std::pow(10.0, (double)abs_dec);
+
+  const double value_mul_tmp = number * tmp;
+  if (!dec_negative && !std::isfinite(value_mul_tmp)) {
+    return number;
+  }
+
+  const double value_div_tmp = number / tmp;
+  if (number >= 0.0) {
+    return decimals < 0 ? std::floor(value_div_tmp) * tmp
+                        : std::floor(value_mul_tmp) / tmp;
+  } else {
+    return decimals < 0 ? std::ceil(value_div_tmp) * tmp
+                        : std::ceil(value_mul_tmp) / tmp;
+  }
+}
+
 } // namespace facebook::velox::functions

velox/functions/prestosql/registration/ArithmeticFunctionsRegistration.cpp

@@ -86,7 +86,8 @@ void registerSimpleFunctions() {
   registerFunction<ToBaseFunction, Varchar, int64_t, int64_t>({"to_base"});
   registerFunction<PiFunction, double>({"pi"});
   registerFunction<EulerConstantFunction, double>({"e"});
-  registerUnaryNumeric<TruncateFunction>({"truncate"});
+  registerFunction<TruncateFunction, double, double>({"truncate"});
+  registerFunction<TruncateFunction, double, double, int32_t>({"truncate"});
 }
 
 } // namespace

velox/functions/prestosql/tests/ArithmeticTest.cpp

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <cmath>
 #include <optional>
 
 #include <gmock/gmock.h>
@@ -33,6 +34,10 @@ MATCHER(IsNan, "is NaN") {
   return arg && std::isnan(*arg);
 }
 
+MATCHER(IsInf, "is Infinity") {
+  return arg && std::isinf(*arg);
+}
+
 class ArithmeticTest : public functions::test::FunctionBaseTest {
  protected:
   template <typename T, typename TExpected = T>
@@ -631,15 +636,49 @@ TEST_F(ArithmeticTest, clamp) {
 }
 
 TEST_F(ArithmeticTest, truncate) {
-  const auto truncate = [&](std::optional<double> a) {
-    return evaluateOnce<double>("truncate(c0)", a);
+  const auto truncate = [&](std::optional<double> a,
+                            std::optional<int32_t> n = 0) {
+    return evaluateOnce<double>("truncate(c0,c1)", a, n);
   };
 
   EXPECT_EQ(truncate(0), 0);
   EXPECT_EQ(truncate(1.5), 1);
   EXPECT_EQ(truncate(-1.5), -1);
   EXPECT_EQ(truncate(std::nullopt), std::nullopt);
   EXPECT_THAT(truncate(kNan), IsNan());
+  EXPECT_THAT(truncate(kInf), IsInf());
+
+  EXPECT_EQ(truncate(0, 0), 0);
+  EXPECT_EQ(truncate(1.5, 0), 1);
+  EXPECT_EQ(truncate(-1.5, 0), -1);
+  EXPECT_EQ(truncate(std::nullopt, 0), std::nullopt);
+  EXPECT_EQ(truncate(1.5, std::nullopt), std::nullopt);
+  EXPECT_THAT(truncate(kNan, 0), IsNan());
+  EXPECT_THAT(truncate(kNan, 1), IsNan());
+  EXPECT_THAT(truncate(kInf, 0), IsInf());
+  EXPECT_THAT(truncate(kInf, 1), IsInf());
+
+  EXPECT_DOUBLE_EQ(truncate(1.5678, 2).value(), 1.56);
+  EXPECT_DOUBLE_EQ(truncate(-1.5678, 2).value(), -1.56);
+  EXPECT_DOUBLE_EQ(truncate(1.333, -1).value(), 0);
+  EXPECT_DOUBLE_EQ(truncate(3.54555, 2).value(), 3.54);
+  EXPECT_DOUBLE_EQ(truncate(1234, 1).value(), 1234);
+  EXPECT_DOUBLE_EQ(truncate(1234, -1).value(), 1230);
+  EXPECT_DOUBLE_EQ(truncate(1234.56, 1).value(), 1234.5);
+  EXPECT_DOUBLE_EQ(truncate(1234.56, -1).value(), 1230.0);
+  EXPECT_DOUBLE_EQ(truncate(1239.999, 2).value(), 1239.99);
+  EXPECT_DOUBLE_EQ(truncate(1239.999, -2).value(), 1200.0);
+  EXPECT_DOUBLE_EQ(
+      truncate(123456789012345678901.23, 3).value(), 123456789012345678901.23);
+  EXPECT_DOUBLE_EQ(
+      truncate(-123456789012345678901.23, 3).value(),
+      -123456789012345678901.23);
+  EXPECT_DOUBLE_EQ(
+      truncate(123456789123456.999, 2).value(), 123456789123456.99);
+  EXPECT_DOUBLE_EQ(truncate(123456789012345678901.0, -21).value(), 0.0);
+  EXPECT_DOUBLE_EQ(truncate(123456789012345678901.23, -21).value(), 0.0);
+  EXPECT_DOUBLE_EQ(truncate(123456789012345678901.0, -21).value(), 0.0);
+  EXPECT_DOUBLE_EQ(truncate(123456789012345678901.23, -21).value(), 0.0);
 }
 
 } // namespace

velox/type/DoubleUtil.cpp

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "velox/type/DoubleUtil.h"
+#include <array>
+
+namespace facebook::velox {
+
+const std::array<double, 309> DoubleUtil::kPowersOfTen = {
+    1e000, 1e001, 1e002, 1e003, 1e004, 1e005, 1e006, 1e007, 1e008, 1e009, 1e010,
+    1e011, 1e012, 1e013, 1e014, 1e015, 1e016, 1e017, 1e018, 1e019, 1e020, 1e021,
+    1e022, 1e023, 1e024, 1e025, 1e026, 1e027, 1e028, 1e029, 1e030, 1e031, 1e032,
+    1e033, 1e034, 1e035, 1e036, 1e037, 1e038, 1e039, 1e040, 1e041, 1e042, 1e043,
+    1e044, 1e045, 1e046, 1e047, 1e048, 1e049, 1e050, 1e051, 1e052, 1e053, 1e054,
+    1e055, 1e056, 1e057, 1e058, 1e059, 1e060, 1e061, 1e062, 1e063, 1e064, 1e065,
+    1e066, 1e067, 1e068, 1e069, 1e070, 1e071, 1e072, 1e073, 1e074, 1e075, 1e076,
+    1e077, 1e078, 1e079, 1e080, 1e081, 1e082, 1e083, 1e084, 1e085, 1e086, 1e087,
+    1e088, 1e089, 1e090, 1e091, 1e092, 1e093, 1e094, 1e095, 1e096, 1e097, 1e098,
+    1e099, 1e100, 1e101, 1e102, 1e103, 1e104, 1e105, 1e106, 1e107, 1e108, 1e109,
+    1e110, 1e111, 1e112, 1e113, 1e114, 1e115, 1e116, 1e117, 1e118, 1e119, 1e120,
+    1e121, 1e122, 1e123, 1e124, 1e125, 1e126, 1e127, 1e128, 1e129, 1e130, 1e131,
+    1e132, 1e133, 1e134, 1e135, 1e136, 1e137, 1e138, 1e139, 1e140, 1e141, 1e142,
+    1e143, 1e144, 1e145, 1e146, 1e147, 1e148, 1e149, 1e150, 1e151, 1e152, 1e153,
+    1e154, 1e155, 1e156, 1e157, 1e158, 1e159, 1e160, 1e161, 1e162, 1e163, 1e164,
+    1e165, 1e166, 1e167, 1e168, 1e169, 1e170, 1e171, 1e172, 1e173, 1e174, 1e175,
+    1e176, 1e177, 1e178, 1e179, 1e180, 1e181, 1e182, 1e183, 1e184, 1e185, 1e186,
+    1e187, 1e188, 1e189, 1e190, 1e191, 1e192, 1e193, 1e194, 1e195, 1e196, 1e197,
+    1e198, 1e199, 1e200, 1e201, 1e202, 1e203, 1e204, 1e205, 1e206, 1e207, 1e208,
+    1e209, 1e210, 1e211, 1e212, 1e213, 1e214, 1e215, 1e216, 1e217, 1e218, 1e219,
+    1e220, 1e221, 1e222, 1e223, 1e224, 1e225, 1e226, 1e227, 1e228, 1e229, 1e230,
+    1e231, 1e232, 1e233, 1e234, 1e235, 1e236, 1e237, 1e238, 1e239, 1e240, 1e241,
+    1e242, 1e243, 1e244, 1e245, 1e246, 1e247, 1e248, 1e249, 1e250, 1e251, 1e252,
+    1e253, 1e254, 1e255, 1e256, 1e257, 1e258, 1e259, 1e260, 1e261, 1e262, 1e263,
+    1e264, 1e265, 1e266, 1e267, 1e268, 1e269, 1e270, 1e271, 1e272, 1e273, 1e274,
+    1e275, 1e276, 1e277, 1e278, 1e279, 1e280, 1e281, 1e282, 1e283, 1e284, 1e285,
+    1e286, 1e287, 1e288, 1e289, 1e290, 1e291, 1e292, 1e293, 1e294, 1e295, 1e296,
+    1e297, 1e298, 1e299, 1e300, 1e301, 1e302, 1e303, 1e304, 1e305, 1e306, 1e307,
+    1e308};
+} // namespace facebook::velox

velox/type/DoubleUtil.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <array>
+
+namespace facebook::velox {
+
+/// A static class that holds helper functions for DOUBLE type.
+class DoubleUtil {
+ public:
+  static const std::array<double, 309> kPowersOfTen;
+
+}; // DoubleUtil
+} // namespace facebook::velox