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     new 93b93aa  [FLINK-9928] Add LOG2 function for table/sql API
93b93aa is described below

commit 93b93aa0857c75a6021d3de8910191d36a1c1c18
Author: yanghua <yanghua1...@gmail.com>
AuthorDate: Tue Jul 24 19:13:39 2018 +0800

    [FLINK-9928] Add LOG2 function for table/sql API
    
    This closes #6404.
---
 docs/dev/table/sql.md                              | 11 +++++++++
 docs/dev/table/tableApi.md                         | 11 +++++++++
 .../flink/table/api/scala/expressionDsl.scala      |  5 ++++
 .../flink/table/codegen/calls/BuiltInMethods.scala |  2 ++
 .../table/codegen/calls/FunctionGenerator.scala    |  6 +++++
 .../flink/table/expressions/mathExpressions.scala  | 12 ++++++++++
 .../table/functions/sql/ScalarSqlFunctions.scala   |  9 ++++++++
 .../table/runtime/functions/ScalarFunctions.scala  | 11 +++++++++
 .../flink/table/validate/FunctionCatalog.scala     |  2 ++
 .../table/expressions/ScalarFunctionsTest.scala    | 27 ++++++++++++++++++++++
 10 files changed, 96 insertions(+)

diff --git a/docs/dev/table/sql.md b/docs/dev/table/sql.md
index 1ed06f0..366e3fd 100644
--- a/docs/dev/table/sql.md
+++ b/docs/dev/table/sql.md
@@ -1411,6 +1411,17 @@ LOG10(numeric)
 
     <tr>
       <td>
+        {% highlight text %}
+LOG2(numeric)
+{% endhighlight %}
+      </td>
+      <td>
+        <p>Returns the base 2 logarithm of <i>numeric</i>.</p>
+      </td>
+    </tr>
+
+    <tr>
+      <td>
        {% highlight text %}
 LOG(x numeric)
 LOG(b numeric, x numeric)
diff --git a/docs/dev/table/tableApi.md b/docs/dev/table/tableApi.md
index b1b8f60..6e202f1 100644
--- a/docs/dev/table/tableApi.md
+++ b/docs/dev/table/tableApi.md
@@ -2070,6 +2070,17 @@ NUMERIC.log10()
     <tr>
       <td>
         {% highlight java %}
+NUMERIC.log2()
+{% endhighlight %}
+      </td>
+      <td>
+        <p>Calculates the base 2 logarithm of given value.</p>
+      </td>
+    </tr>
+
+    <tr>
+      <td>
+        {% highlight java %}
 numeric1.log()
 numeric1.log(numeric2)
 {% endhighlight %}
diff --git 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/scala/expressionDsl.scala
 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/scala/expressionDsl.scala
index 62c62b1..35d2167 100644
--- 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/scala/expressionDsl.scala
+++ 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/scala/expressionDsl.scala
@@ -301,6 +301,11 @@ trait ImplicitExpressionOperations {
   def log10() = Log10(expr)
 
   /**
+    * Calculates the base 2 logarithm of the given value.
+    */
+  def log2() = Log2(expr)
+
+  /**
     * Calculates the natural logarithm of the given value.
     */
   def ln() = Ln(expr)
diff --git 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/BuiltInMethods.scala
 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/BuiltInMethods.scala
index 22298da..0e0f709 100644
--- 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/BuiltInMethods.scala
+++ 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/BuiltInMethods.scala
@@ -33,6 +33,8 @@ object BuiltInMethods {
 
   val LOG10 = Types.lookupMethod(classOf[Math], "log10", classOf[Double])
 
+  val LOG2 = Types.lookupMethod(classOf[ScalarFunctions], "log2", 
classOf[Double])
+
   val EXP = Types.lookupMethod(classOf[Math], "exp", classOf[Double])
 
   val POWER = Types.lookupMethod(classOf[Math], "pow", classOf[Double], 
classOf[Double])
diff --git 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/FunctionGenerator.scala
 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/FunctionGenerator.scala
index d264cce..a5c275a 100644
--- 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/FunctionGenerator.scala
+++ 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/codegen/calls/FunctionGenerator.scala
@@ -163,6 +163,12 @@ object FunctionGenerator {
     BuiltInMethods.LOG10)
 
   addSqlFunctionMethod(
+    LOG2,
+    Seq(DOUBLE_TYPE_INFO),
+    DOUBLE_TYPE_INFO,
+    BuiltInMethods.LOG2)
+
+  addSqlFunctionMethod(
     LN,
     Seq(DOUBLE_TYPE_INFO),
     DOUBLE_TYPE_INFO,
diff --git 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/mathExpressions.scala
 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/mathExpressions.scala
index 0378ce5..10ba007 100644
--- 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/mathExpressions.scala
+++ 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/mathExpressions.scala
@@ -92,6 +92,18 @@ case class Log10(child: Expression) extends UnaryExpression 
with InputTypeSpec {
   }
 }
 
+case class Log2(child: Expression) extends UnaryExpression with InputTypeSpec {
+  override private[flink] def expectedTypes: Seq[TypeInformation[_]] = 
DOUBLE_TYPE_INFO :: Nil
+
+  override private[flink] def resultType: TypeInformation[_] = DOUBLE_TYPE_INFO
+
+  override private[flink] def toRexNode(implicit relBuilder: RelBuilder) = {
+    relBuilder.call(ScalarSqlFunctions.LOG2, child.toRexNode)
+  }
+
+  override def toString: String = s"log2($child)"
+}
+
 case class Log(base: Expression, antilogarithm: Expression) extends Expression 
with InputTypeSpec {
   def this(antilogarithm: Expression) = this(null, antilogarithm)
 
diff --git 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/sql/ScalarSqlFunctions.scala
 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/sql/ScalarSqlFunctions.scala
index 1af1e68..49fda9d 100644
--- 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/sql/ScalarSqlFunctions.scala
+++ 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/sql/ScalarSqlFunctions.scala
@@ -67,6 +67,15 @@ object ScalarSqlFunctions {
       OperandTypes.family(SqlTypeFamily.NUMERIC, SqlTypeFamily.NUMERIC)),
     SqlFunctionCategory.NUMERIC)
 
+  val LOG2 = new SqlFunction(
+    "LOG2",
+    SqlKind.OTHER_FUNCTION,
+    ReturnTypes.DOUBLE_NULLABLE,
+    null,
+    OperandTypes.NUMERIC,
+    SqlFunctionCategory.NUMERIC
+  )
+
   val LPAD = new SqlFunction(
     "LPAD",
     SqlKind.OTHER_FUNCTION,
diff --git 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/functions/ScalarFunctions.scala
 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/functions/ScalarFunctions.scala
index 40f1ec3..50e8f9c 100644
--- 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/functions/ScalarFunctions.scala
+++ 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/functions/ScalarFunctions.scala
@@ -111,6 +111,17 @@ object ScalarFunctions {
   }
 
   /**
+    * Returns the logarithm of "x" with base 2.
+    */
+  def log2(x: Double): Double = {
+    if (x <= 0.0) {
+      throw new IllegalArgumentException(s"x of 'log2(x)' must be > 0, but x = 
$x")
+    } else {
+      Math.log(x) / Math.log(2)
+    }
+  }
+
+  /**
     * Returns the string str left-padded with the string pad to a length of 
len characters.
     * If str is longer than len, the return value is shortened to len 
characters.
     */
diff --git 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/validate/FunctionCatalog.scala
 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/validate/FunctionCatalog.scala
index b4f0424..8a91340 100644
--- 
a/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/validate/FunctionCatalog.scala
+++ 
b/flink-libraries/flink-table/src/main/scala/org/apache/flink/table/validate/FunctionCatalog.scala
@@ -214,6 +214,7 @@ object FunctionCatalog {
     "exp" -> classOf[Exp],
     "floor" -> classOf[Floor],
     "log10" -> classOf[Log10],
+    "log2" -> classOf[Log2],
     "ln" -> classOf[Ln],
     "log" -> classOf[Log],
     "power" -> classOf[Power],
@@ -398,6 +399,7 @@ class BasicOperatorTable extends ReflectiveSqlOperatorTable 
{
     SqlStdOperatorTable.MOD,
     SqlStdOperatorTable.LN,
     SqlStdOperatorTable.LOG10,
+    ScalarSqlFunctions.LOG2,
     SqlStdOperatorTable.ABS,
     SqlStdOperatorTable.EXP,
     SqlStdOperatorTable.NULLIF,
diff --git 
a/flink-libraries/flink-table/src/test/scala/org/apache/flink/table/expressions/ScalarFunctionsTest.scala
 
b/flink-libraries/flink-table/src/test/scala/org/apache/flink/table/expressions/ScalarFunctionsTest.scala
index 995762a..4eb2e33 100644
--- 
a/flink-libraries/flink-table/src/test/scala/org/apache/flink/table/expressions/ScalarFunctionsTest.scala
+++ 
b/flink-libraries/flink-table/src/test/scala/org/apache/flink/table/expressions/ScalarFunctionsTest.scala
@@ -576,6 +576,33 @@ class ScalarFunctionsTest extends ScalarTypesTestBase {
   }
 
   @Test
+  def testLog2(): Unit = {
+    testAllApis(
+      'f6.log2(),
+      "f6.log2",
+      "LOG2(f6)",
+     "2.2016338611696504")
+
+    testAllApis(
+      ('f6 - 'f6 + 100).log2(),
+      "(f6 - f6 + 100).log2()",
+      "LOG2(f6 - f6 + 100)",
+      "6.643856189774725")
+
+    testAllApis(
+      ('f6 + 20).log2(),
+      "(f6+20).log2",
+      "LOG2(f6+20)",
+      "4.620586410451877")
+
+    testAllApis(
+      10.log2(),
+      "10.log2",
+      "LOG2(10)",
+      "3.3219280948873626")
+  }
+
+  @Test
   def testPower(): Unit = {
     // f7: int , f4: long, f6: double
     testAllApis(

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