Support mathematical functions rand and constants e, pi (#591)

* support e, pi, rand

* updated doc

* update

* update

* update

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/expression/DSL.java

@@ -21,7 +21,6 @@
 import com.amazon.opendistroforelasticsearch.sql.expression.aggregation.Aggregator;
 import com.amazon.opendistroforelasticsearch.sql.expression.function.BuiltinFunctionName;
 import com.amazon.opendistroforelasticsearch.sql.expression.function.BuiltinFunctionRepository;
-import com.amazon.opendistroforelasticsearch.sql.expression.function.FunctionName;
 import java.util.Arrays;
 import lombok.RequiredArgsConstructor;
 
@@ -81,6 +80,10 @@ public FunctionExpression crc32(Expression... expressions) {
     return function(BuiltinFunctionName.CRC32, expressions);
   }
 
+  public FunctionExpression euler(Expression... expressions) {
+    return function(BuiltinFunctionName.E, expressions);
+  }
+
   public FunctionExpression exp(Expression... expressions) {
     return function(BuiltinFunctionName.EXP, expressions);
   }
@@ -109,6 +112,10 @@ public FunctionExpression mod(Expression... expressions) {
     return function(BuiltinFunctionName.MOD, expressions);
   }
 
+  public FunctionExpression pi(Expression... expressions) {
+    return function(BuiltinFunctionName.PI, expressions);
+  }
+
   public FunctionExpression pow(Expression... expressions) {
     return function(BuiltinFunctionName.POW, expressions);
   }
@@ -117,6 +124,10 @@ public FunctionExpression power(Expression... expressions) {
     return function(BuiltinFunctionName.POWER, expressions);
   }
 
+  public FunctionExpression rand(Expression... expressions) {
+    return function(BuiltinFunctionName.RAND, expressions);
+  }
+
   public FunctionExpression round(Expression... expressions) {
     return function(BuiltinFunctionName.ROUND, expressions);
   }

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/expression/function/BuiltinFunctionName.java

@@ -20,15 +20,18 @@ public enum BuiltinFunctionName {
   CEILING(FunctionName.of("ceiling")),
   CONV(FunctionName.of("conv")),
   CRC32(FunctionName.of("crc32")),
+  E(FunctionName.of("e")),
   EXP(FunctionName.of("exp")),
   FLOOR(FunctionName.of("floor")),
   LN(FunctionName.of("ln")),
   LOG(FunctionName.of("log")),
   LOG10(FunctionName.of("log10")),
   LOG2(FunctionName.of("log2")),
   MOD(FunctionName.of("mod")),
+  PI(FunctionName.of("pi")),
   POW(FunctionName.of("pow")),
   POWER(FunctionName.of("power")),
+  RAND(FunctionName.of("rand")),
   ROUND(FunctionName.of("round")),
   SIGN(FunctionName.of("sign")),
   SQRT(FunctionName.of("sqrt")),

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/expression/operator/OperatorUtils.java

@@ -29,6 +29,7 @@
 import java.util.function.BiFunction;
 import java.util.function.BiPredicate;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Collectors;
 import lombok.experimental.UtilityClass;
 
@@ -257,6 +258,36 @@ public String toString() {
         };
   }
 
+  /**
+   * Construct {@link FunctionBuilder} which call function with no argument.
+   *
+   * @param functionName function name
+   * @param function     {@link Function}
+   * @param returnType   return type
+   * @param <T>          the type of the result to the function
+   * @return {@link FunctionBuilder}
+   */
+  public static <T> FunctionBuilder noArgFunction(FunctionName functionName,
+                                                  Supplier<T> function,
+                                                  ExprCoreType returnType) {
+    return arguments -> new FunctionExpression(functionName, arguments) {
+      @Override
+      public ExprValue valueOf(Environment<Expression, ExprValue> valueEnv) {
+        return ExprValueUtils.fromObjectValue(function.get());
+      }
+
+      @Override
+      public ExprType type() {
+        return returnType;
+      }
+
+      @Override
+      public String toString() {
+        return String.format("%s()", functionName);
+      }
+    };
+  }
+
   /**
    * String comparator.
    */

core/src/main/java/com/amazon/opendistroforelasticsearch/sql/expression/operator/arthmetic/MathematicalFunction.java

@@ -16,6 +16,7 @@
 package com.amazon.opendistroforelasticsearch.sql.expression.operator.arthmetic;
 
 import static com.amazon.opendistroforelasticsearch.sql.expression.operator.OperatorUtils.doubleArgFunc;
+import static com.amazon.opendistroforelasticsearch.sql.expression.operator.OperatorUtils.noArgFunction;
 import static com.amazon.opendistroforelasticsearch.sql.expression.operator.OperatorUtils.tripleArgFunc;
 import static com.amazon.opendistroforelasticsearch.sql.expression.operator.OperatorUtils.unaryOperator;
 
@@ -31,7 +32,9 @@
 import java.math.BigDecimal;
 import java.math.RoundingMode;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Map;
+import java.util.Random;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 import java.util.zip.CRC32;
@@ -50,6 +53,7 @@ public static void register(BuiltinFunctionRepository repository) {
     repository.register(ceiling());
     repository.register(conv());
     repository.register(crc32());
+    repository.register(euler());
     repository.register(exp());
     repository.register(floor());
     repository.register(ln());
@@ -63,6 +67,8 @@ public static void register(BuiltinFunctionRepository repository) {
     repository.register(sign());
     repository.register(sqrt());
     repository.register(truncate());
+    repository.register(pi());
+    repository.register(rand());
   }
 
   /**
@@ -164,6 +170,20 @@ private static FunctionResolver crc32() {
             .build());
   }
 
+  /**
+   * Definition of e() function.
+   * Get the Euler's number.
+   * () -> DOUBLE
+   */
+  private static FunctionResolver euler() {
+    FunctionName functionName = BuiltinFunctionName.E.getName();
+    return new FunctionResolver(functionName,
+        new ImmutableMap.Builder<FunctionSignature, FunctionBuilder>()
+            .put(new FunctionSignature(functionName, Collections.emptyList()),
+                noArgFunction(functionName, () -> Math.E, ExprCoreType.DOUBLE))
+            .build());
+  }
+
   /**
    * Definition of exp(x) function. Calculate exponent function e to the x The supported signature
    * of exp function is INTEGER/LONG/FLOAT/DOUBLE -> DOUBLE
@@ -266,6 +286,20 @@ private static FunctionResolver mod() {
             (v1, v2) -> v2 == 0 ? null : v1 % v2));
   }
 
+  /**
+   * Definition of pi() function.
+   * Get the value of pi.
+   * () -> DOUBLE
+   */
+  private static FunctionResolver pi() {
+    FunctionName functionName = BuiltinFunctionName.PI.getName();
+    return new FunctionResolver(functionName,
+        new ImmutableMap.Builder<FunctionSignature, FunctionBuilder>()
+            .put(new FunctionSignature(functionName, Collections.emptyList()),
+                noArgFunction(functionName, () -> Math.PI, ExprCoreType.DOUBLE))
+            .build());
+  }
+
   /**
    * Definition of pow(x, y)/power(x, y) function.
    * Calculate the value of x raised to the power of y
@@ -285,6 +319,30 @@ private static FunctionResolver power() {
     return new FunctionResolver(functionName, doubleArgumentsFunction(functionName, Math::pow));
   }
 
+  /**
+   * Definition of rand() and rand(N) function.
+   * rand() returns a random floating-point value in the range 0 <= value < 1.0
+   * If integer N is specified, the seed is initialized prior to execution.
+   * One implication of this behavior is with identical argument N,rand(N) returns the same value
+   * each time, and thus produces a repeatable sequence of column values.
+   * The supported signature of rand function is
+   * ([INTEGER]) -> FLOAT
+   */
+  private static FunctionResolver rand() {
+    FunctionName functionName = BuiltinFunctionName.RAND.getName();
+    return new FunctionResolver(functionName,
+        new ImmutableMap.Builder<FunctionSignature, FunctionBuilder>()
+            .put(
+                new FunctionSignature(functionName, Collections.emptyList()),
+                noArgFunction(functionName, () -> new Random().nextFloat(), ExprCoreType.FLOAT))
+            .put(
+                new FunctionSignature(functionName, Arrays.asList(ExprCoreType.INTEGER)),
+                unaryOperator(
+                    functionName, n -> new Random(n).nextFloat(), ExprValueUtils::getIntegerValue,
+                    ExprCoreType.FLOAT))
+            .build());
+  }
+
   /**
    * Definition of round(x)/round(x, d) function.
    * Rounds the argument x to d decimal places, d defaults to 0 if not specified.

core/src/test/java/com/amazon/opendistroforelasticsearch/sql/expression/operator/arthmetic/MathematicalFunctionTest.java

@@ -22,6 +22,7 @@
 import static com.amazon.opendistroforelasticsearch.sql.config.TestConfig.STRING_TYPE_MISSING_VALUE_FILED;
 import static com.amazon.opendistroforelasticsearch.sql.config.TestConfig.STRING_TYPE_NULL_VALUE_FILED;
 import static com.amazon.opendistroforelasticsearch.sql.data.model.ExprValueUtils.getDoubleValue;
+import static com.amazon.opendistroforelasticsearch.sql.data.model.ExprValueUtils.getFloatValue;
 import static com.amazon.opendistroforelasticsearch.sql.data.type.ExprCoreType.DOUBLE;
 import static com.amazon.opendistroforelasticsearch.sql.data.type.ExprCoreType.FLOAT;
 import static com.amazon.opendistroforelasticsearch.sql.data.type.ExprCoreType.INTEGER;
@@ -35,16 +36,12 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
-import com.amazon.opendistroforelasticsearch.sql.data.model.ExprValue;
-import com.amazon.opendistroforelasticsearch.sql.data.model.ExprValueUtils;
 import com.amazon.opendistroforelasticsearch.sql.expression.DSL;
 import com.amazon.opendistroforelasticsearch.sql.expression.ExpressionTestBase;
 import com.amazon.opendistroforelasticsearch.sql.expression.FunctionExpression;
-import com.google.common.collect.Lists;
 import java.math.BigDecimal;
 import java.math.RoundingMode;
-import java.util.List;
-import java.util.stream.Collectors;
+import java.util.Random;
 import java.util.stream.Stream;
 import java.util.zip.CRC32;
 import org.junit.jupiter.api.DisplayNameGeneration;
@@ -425,6 +422,15 @@ public void crc32_missing_value() {
     assertTrue(crc.valueOf(valueEnv()).isMissing());
   }
 
+  /**
+   * Test constant e.
+   */
+  @Test
+  public void test_e() {
+    FunctionExpression e = dsl.euler();
+    assertThat(e.valueOf(valueEnv()), allOf(hasType(DOUBLE), hasValue(Math.E)));
+  }
+
   /**
    * Test exp with integer value.
    */
@@ -1717,4 +1723,48 @@ public void truncate_null_missing() {
     assertEquals(LONG, truncate.type());
     assertTrue(truncate.valueOf(valueEnv()).isMissing());
   }
+
+  /**
+   * Test constant pi.
+   */
+  @Test
+  public void test_pi() {
+    FunctionExpression pi = dsl.pi();
+    assertThat(pi.valueOf(valueEnv()), allOf(hasType(DOUBLE), hasValue(Math.PI)));
+  }
+
+  /**
+   * Test rand with no argument.
+   */
+  @Test
+  public void rand_no_arg() {
+    FunctionExpression rand = dsl.rand();
+    assertEquals(FLOAT, rand.type());
+    assertTrue(
+        getFloatValue(rand.valueOf(valueEnv())) >= 0
+            && getFloatValue(rand.valueOf(valueEnv())) < 1);
+    assertEquals("rand()", rand.toString());
+  }
+
+  /**
+   * Test rand with integer value.
+   */
+  @ParameterizedTest(name = "rand({0})")
+  @ValueSource(ints = {2, 3})
+  public void rand_int_value(Integer n) {
+    FunctionExpression rand = dsl.rand(DSL.literal(n));
+    assertEquals(FLOAT, rand.type());
+    assertTrue(
+        getFloatValue(rand.valueOf(valueEnv())) >= 0
+        && getFloatValue(rand.valueOf(valueEnv())) < 1);
+    assertEquals(getFloatValue(rand.valueOf(valueEnv())), new Random(n).nextFloat());
+    assertEquals(String.format("rand(%s)", n), rand.toString());
+  }
+
+  @Test
+  public void rand_null_value() {
+    FunctionExpression rand = dsl.rand(DSL.ref(INT_TYPE_NULL_VALUE_FIELD, INTEGER));
+    assertEquals(FLOAT, rand.type());
+    assertTrue(rand.valueOf(valueEnv()).isNull());
+  }
 }

docs/user/dql/functions.rst

@@ -291,9 +291,19 @@ E
 Description
 -----------
 
-Specifications: 
+Usage: E() returns the Euler's number
 
-1. E() -> DOUBLE
+Return type: DOUBLE
+
+Example::
+
+    od> SELECT E()
+    fetched rows / total rows = 1/1
+    +-------------------+
+    | e()               |
+    |-------------------|
+    | 2.718281828459045 |
+    +-------------------+
 
 
 EXP
@@ -548,9 +558,19 @@ PI
 Description
 -----------
 
-Specifications: 
+Usage: PI() returns the constant pi
+
+Return type: DOUBLE
 
-1. PI() -> DOUBLE
+Example::
+
+    od> SELECT PI()
+    fetched rows / total rows = 1/1
+    +-------------------+
+    | pi()              |
+    |-------------------|
+    | 3.141592653589793 |
+    +-------------------+
 
 
 POW
@@ -616,10 +636,21 @@ RAND
 Description
 -----------
 
-Specifications: 
+Usage: RAND()/RAND(N) returns a random floating-point value in the range 0 <= value < 1.0. If integer N is specified, the seed is initialized prior to execution. One implication of this behavior is with identical argument N, rand(N) returns the same value each time, and thus produces a repeatable sequence of column values.
+
+Argument type: INTEGER
 
-1. RAND() -> NUMBER
-2. RAND(NUMBER T) -> T
+Return type: FLOAT
+
+Example::
+
+    od> SELECT RAND(3)
+    fetched rows / total rows = 1/1
+    +------------+
+    | rand(3)    |
+    |------------|
+    | 0.73105735 |
+    +------------+
 
 
 REPLACE