[SPARK-17246][SQL] Add BigDecimal literal

## What changes were proposed in this pull request?
This PR adds parser support for `BigDecimal` literals. If you append the suffix `BD` to a valid number then this will be interpreted as a `BigDecimal`, for example `12.0E10BD` will interpreted into a BigDecimal with scale -9 and precision 3. This is useful in situations where you need exact values.

## How was this patch tested?
Added tests to `ExpressionParserSuite`, `ExpressionSQLBuilderSuite` and `SQLQueryTestSuite`.

Author: Herman van Hovell <hvanhovell@databricks.com>

Closes #14819 from hvanhovell/SPARK-17246.

4 files changed, 29 insertions, 2 deletions

diff --git a/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4 b/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4
index cab7c3ff5a..a8af840c1e 100644
--- a/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4
+++ b/sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4
@@ -633,6 +633,7 @@ number
     | MINUS? SMALLINT_LITERAL         #smallIntLiteral
     | MINUS? TINYINT_LITERAL          #tinyIntLiteral
     | MINUS? DOUBLE_LITERAL           #doubleLiteral
+    | MINUS? BIGDECIMAL_LITERAL       #bigDecimalLiteral
     ;
 
 nonReserved
@@ -928,6 +929,11 @@ DOUBLE_LITERAL
     (INTEGER_VALUE | DECIMAL_VALUE | SCIENTIFIC_DECIMAL_VALUE) 'D'
     ;
 
+BIGDECIMAL_LITERAL
+    :
+    (INTEGER_VALUE | DECIMAL_VALUE | SCIENTIFIC_DECIMAL_VALUE) 'BD'
+    ;
+
 IDENTIFIER
     : (LETTER | DIGIT | '_')+
     ;
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
index 730a7f62e0..41e3952f0e 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/literals.scala
@@ -266,7 +266,7 @@ case class Literal (value: Any, dataType: DataType) extends LeafExpression with
         case Double.NegativeInfinity => s"CAST('-Infinity' AS ${DoubleType.sql})"
         case _ => v + "D"
       }
-    case (v: Decimal, t: DecimalType) => s"CAST($v AS ${t.sql})"
+    case (v: Decimal, t: DecimalType) => v + "BD"
     case (v: Int, DateType) => s"DATE '${DateTimeUtils.toJavaDate(v)}'"
     case (v: Long, TimestampType) => s"TIMESTAMP('${DateTimeUtils.toJavaTimestamp(v)}')"
     case _ => value.toString
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
index 8b98efcbf3..893db93368 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
@@ -26,7 +26,8 @@ import org.antlr.v4.runtime.{ParserRuleContext, Token}
 import org.antlr.v4.runtime.tree.{ParseTree, RuleNode, TerminalNode}
 
 import org.apache.spark.internal.Logging
-import org.apache.spark.sql.catalyst.{FunctionIdentifier, InternalRow, TableIdentifier}
+import org.apache.spark.sql.AnalysisException
+import org.apache.spark.sql.catalyst.{FunctionIdentifier, TableIdentifier}
 import org.apache.spark.sql.catalyst.analysis._
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.parser.SqlBaseParser._
@@ -1324,6 +1325,19 @@ class AstBuilder extends SqlBaseBaseVisitor[AnyRef] with Logging {
   }
 
   /**
+   * Create a BigDecimal Literal expression.
+   */
+  override def visitBigDecimalLiteral(ctx: BigDecimalLiteralContext): Literal = {
+    val raw = ctx.getText.substring(0, ctx.getText.length - 2)
+    try {
+      Literal(BigDecimal(raw).underlying())
+    } catch {
+      case e: AnalysisException =>
+        throw new ParseException(e.message, ctx)
+    }
+  }
+
+  /**
    * Create a String literal expression.
    */
   override def visitStringLiteral(ctx: StringLiteralContext): Literal = withOrigin(ctx) {
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala
index 401d9cd9d2..dbc5db39ae 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala
@@ -392,6 +392,13 @@ class ExpressionParserSuite extends PlanTest {
     intercept("1.8E308D", s"does not fit in range")
     // TODO we need to figure out if we should throw an exception here!
     assertEqual("1E309", Literal(Double.PositiveInfinity))
+
+    // BigDecimal Literal
+    assertEqual("90912830918230182310293801923652346786BD",
+      Literal(BigDecimal("90912830918230182310293801923652346786").underlying()))
+    assertEqual("123.0E-28BD", Literal(BigDecimal("123.0E-28").underlying()))
+    assertEqual("123.08BD", Literal(BigDecimal("123.08").underlying()))
+    intercept("1.20E-38BD", "DecimalType can only support precision up to 38")
   }
 
   test("strings") {