[SPARK-16714][SPARK-16735][SPARK-16646] array, map, greatest, least's type coercion should handle decimal type

## What changes were proposed in this pull request?

Here is a table about the behaviours of `array`/`map` and `greatest`/`least` in Hive, MySQL and Postgres:

|    |Hive|MySQL|Postgres|
|---|---|---|---|---|
|`array`/`map`|can find a wider type with decimal type arguments, and will truncate the wider decimal type if necessary|can find a wider type with decimal type arguments, no truncation problem|can find a wider type with decimal type arguments, no truncation problem|
|`greatest`/`least`|can find a wider type with decimal type arguments, and truncate if necessary, but can't do string promotion|can find a wider type with decimal type arguments, no truncation problem, but can't do string promotion|can find a wider type with decimal type arguments, no truncation problem, but can't do string promotion|

I think these behaviours makes sense and Spark SQL should follow them.

This PR fixes `array` and `map` by using `findWiderCommonType` to get the wider type.
This PR fixes `greatest` and `least` by add a `findWiderTypeWithoutStringPromotion`, which provides similar semantic of `findWiderCommonType`, but without string promotion.

## How was this patch tested?

new tests in `TypeCoersionSuite`

Author: Wenchen Fan <wenchen@databricks.com>
Author: Yin Huai <yhuai@databricks.com>

Closes #14439 from cloud-fan/bug.

2 files changed, 67 insertions, 1 deletions

diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/ExpressionTypeCheckingSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/ExpressionTypeCheckingSuite.scala
index 35f75697b7..542e654bbc 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/ExpressionTypeCheckingSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/ExpressionTypeCheckingSuite.scala
@@ -209,7 +209,6 @@ class ExpressionTypeCheckingSuite extends SparkFunSuite {
     for (operator <- Seq[(Seq[Expression] => Expression)](Greatest, Least)) {
       assertError(operator(Seq('booleanField)), "requires at least 2 arguments")
       assertError(operator(Seq('intField, 'stringField)), "should all have the same type")
-      assertError(operator(Seq('intField, 'decimalField)), "should all have the same type")
       assertError(operator(Seq('mapField, 'mapField)), "does not support ordering")
     }
   }
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercionSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercionSuite.scala
index 971c99b671..a13c45fe2f 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercionSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercionSuite.scala
@@ -283,6 +283,24 @@ class TypeCoercionSuite extends PlanTest {
         :: Cast(Literal(1), StringType)
         :: Cast(Literal("a"), StringType)
         :: Nil))
+
+    ruleTest(TypeCoercion.FunctionArgumentConversion,
+      CreateArray(Literal.create(null, DecimalType(5, 3))
+        :: Literal(1)
+        :: Nil),
+      CreateArray(Literal.create(null, DecimalType(5, 3)).cast(DecimalType(13, 3))
+        :: Literal(1).cast(DecimalType(13, 3))
+        :: Nil))
+
+    ruleTest(TypeCoercion.FunctionArgumentConversion,
+      CreateArray(Literal.create(null, DecimalType(5, 3))
+        :: Literal.create(null, DecimalType(22, 10))
+        :: Literal.create(null, DecimalType(38, 38))
+        :: Nil),
+      CreateArray(Literal.create(null, DecimalType(5, 3)).cast(DecimalType(38, 38))
+        :: Literal.create(null, DecimalType(22, 10)).cast(DecimalType(38, 38))
+        :: Literal.create(null, DecimalType(38, 38)).cast(DecimalType(38, 38))
+        :: Nil))
   }
 
   test("CreateMap casts") {
@@ -298,6 +316,17 @@ class TypeCoercionSuite extends PlanTest {
         :: Cast(Literal.create(2.0, FloatType), FloatType)
         :: Literal("b")
         :: Nil))
+    ruleTest(TypeCoercion.FunctionArgumentConversion,
+      CreateMap(Literal.create(null, DecimalType(5, 3))
+        :: Literal("a")
+        :: Literal.create(2.0, FloatType)
+        :: Literal("b")
+        :: Nil),
+      CreateMap(Literal.create(null, DecimalType(5, 3)).cast(DoubleType)
+        :: Literal("a")
+        :: Literal.create(2.0, FloatType).cast(DoubleType)
+        :: Literal("b")
+        :: Nil))
     // type coercion for map values
     ruleTest(TypeCoercion.FunctionArgumentConversion,
       CreateMap(Literal(1)
@@ -310,6 +339,17 @@ class TypeCoercionSuite extends PlanTest {
         :: Literal(2)
         :: Cast(Literal(3.0), StringType)
         :: Nil))
+    ruleTest(TypeCoercion.FunctionArgumentConversion,
+      CreateMap(Literal(1)
+        :: Literal.create(null, DecimalType(38, 0))
+        :: Literal(2)
+        :: Literal.create(null, DecimalType(38, 38))
+        :: Nil),
+      CreateMap(Literal(1)
+        :: Literal.create(null, DecimalType(38, 0)).cast(DecimalType(38, 38))
+        :: Literal(2)
+        :: Literal.create(null, DecimalType(38, 38)).cast(DecimalType(38, 38))
+        :: Nil))
     // type coercion for both map keys and values
     ruleTest(TypeCoercion.FunctionArgumentConversion,
       CreateMap(Literal(1)
@@ -344,6 +384,33 @@ class TypeCoercionSuite extends PlanTest {
           :: Cast(Literal(1), DecimalType(22, 0))
           :: Cast(Literal(new java.math.BigDecimal("1000000000000000000000")), DecimalType(22, 0))
           :: Nil))
+      ruleTest(TypeCoercion.FunctionArgumentConversion,
+        operator(Literal(1.0)
+          :: Literal.create(null, DecimalType(10, 5))
+          :: Literal(1)
+          :: Nil),
+        operator(Literal(1.0).cast(DoubleType)
+          :: Literal.create(null, DecimalType(10, 5)).cast(DoubleType)
+          :: Literal(1).cast(DoubleType)
+          :: Nil))
+      ruleTest(TypeCoercion.FunctionArgumentConversion,
+        operator(Literal.create(null, DecimalType(15, 0))
+          :: Literal.create(null, DecimalType(10, 5))
+          :: Literal(1)
+          :: Nil),
+        operator(Literal.create(null, DecimalType(15, 0)).cast(DecimalType(20, 5))
+          :: Literal.create(null, DecimalType(10, 5)).cast(DecimalType(20, 5))
+          :: Literal(1).cast(DecimalType(20, 5))
+          :: Nil))
+      ruleTest(TypeCoercion.FunctionArgumentConversion,
+        operator(Literal.create(2L, LongType)
+          :: Literal(1)
+          :: Literal.create(null, DecimalType(10, 5))
+          :: Nil),
+        operator(Literal.create(2L, LongType).cast(DecimalType(25, 5))
+          :: Literal(1).cast(DecimalType(25, 5))
+          :: Literal.create(null, DecimalType(10, 5)).cast(DecimalType(25, 5))
+          :: Nil))
     }
   }