[SPARK-24468][SQL] Handle negative scale when adjusting precision for…

… decimal operations

## What changes were proposed in this pull request?

In SPARK-22036 we introduced the possibility to allow precision loss in arithmetic operations (according to the SQL standard). The implementation was drawn from Hive's one, where Decimals with a negative scale are not allowed in the operations.

The PR handles the case when the scale is negative, removing the assertion that it is not.

## How was this patch tested?

added UTs

Author: Marco Gaido <[email protected]>

Closes #21499 from mgaido91/SPARK-24468.

sql/catalyst/src/main/scala/org/apache/spark/sql/types/DecimalType.scala

@@ -161,13 +161,17 @@ object DecimalType extends AbstractDataType {
    * This method is used only when `spark.sql.decimalOperations.allowPrecisionLoss` is set to true.
    */
   private[sql] def adjustPrecisionScale(precision: Int, scale: Int): DecimalType = {
-    // Assumptions:
+    // Assumption:
     assert(precision >= scale)
-    assert(scale >= 0)
 
     if (precision <= MAX_PRECISION) {
       // Adjustment only needed when we exceed max precision
       DecimalType(precision, scale)
+    } else if (scale < 0) {
+      // Decimal can have negative scale (SPARK-24468). In this case, we cannot allow a precision
+      // loss since we would cause a loss of digits in the integer part.
+      // In this case, we are likely to meet an overflow.
+      DecimalType(MAX_PRECISION, scale)
     } else {
       // Precision/scale exceed maximum precision. Result must be adjusted to MAX_PRECISION.
       val intDigits = precision - scale

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/DecimalPrecisionSuite.scala

@@ -272,6 +272,15 @@ class DecimalPrecisionSuite extends AnalysisTest with BeforeAndAfter {
     }
   }
 
+  test("SPARK-24468: operations on decimals with negative scale") {
+    val a = AttributeReference("a", DecimalType(3, -10))()
+    val b = AttributeReference("b", DecimalType(1, -1))()
+    val c = AttributeReference("c", DecimalType(35, 1))()
+    checkType(Multiply(a, b), DecimalType(5, -11))
+    checkType(Multiply(a, c), DecimalType(38, -9))
+    checkType(Multiply(b, c), DecimalType(37, 0))
+  }
+
   /** strength reduction for integer/decimal comparisons */
   def ruleTest(initial: Expression, transformed: Expression): Unit = {
     val testRelation = LocalRelation(AttributeReference("a", IntegerType)())

sql/core/src/test/resources/sql-tests/inputs/typeCoercion/native/decimalArithmeticOperations.sql

@@ -40,12 +40,14 @@ select 10.3000 * 3.0;
 select 10.30000 * 30.0;
 select 10.300000000000000000 * 3.000000000000000000;
 select 10.300000000000000000 * 3.0000000000000000000;
+select 2.35E10 * 1.0;
 
 -- arithmetic operations causing an overflow return NULL
 select (5e36 + 0.1) + 5e36;
 select (-4e36 - 0.1) - 7e36;
 select 12345678901234567890.0 * 12345678901234567890.0;
 select 1e35 / 0.1;
+select 1.2345678901234567890E30 * 1.2345678901234567890E25;
 
 -- arithmetic operations causing a precision loss are truncated
 select 12345678912345678912345678912.1234567 + 9999999999999999999999999999999.12345;
@@ -67,12 +69,14 @@ select 10.3000 * 3.0;
 select 10.30000 * 30.0;
 select 10.300000000000000000 * 3.000000000000000000;
 select 10.300000000000000000 * 3.0000000000000000000;
+select 2.35E10 * 1.0;
 
 -- arithmetic operations causing an overflow return NULL
 select (5e36 + 0.1) + 5e36;
 select (-4e36 - 0.1) - 7e36;
 select 12345678901234567890.0 * 12345678901234567890.0;
 select 1e35 / 0.1;
+select 1.2345678901234567890E30 * 1.2345678901234567890E25;
 
 -- arithmetic operations causing a precision loss return NULL
 select 12345678912345678912345678912.1234567 + 9999999999999999999999999999999.12345;

sql/core/src/test/resources/sql-tests/results/typeCoercion/native/decimalArithmeticOperations.sql.out

@@ -1,5 +1,5 @@
 -- Automatically generated by SQLQueryTestSuite
--- Number of queries: 36
+-- Number of queries: 40
 
 
 -- !query 0
@@ -114,190 +114,222 @@ struct<(CAST(10.300000000000000000 AS DECIMAL(21,19)) * CAST(3.00000000000000000
 
 
 -- !query 13
-select (5e36 + 0.1) + 5e36
+select 2.35E10 * 1.0
 -- !query 13 schema
-struct<(CAST((CAST(5E+36 AS DECIMAL(38,1)) + CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) + CAST(5E+36 AS DECIMAL(38,1))):decimal(38,1)>
+struct<(CAST(2.35E+10 AS DECIMAL(12,1)) * CAST(1.0 AS DECIMAL(12,1))):decimal(6,-7)>
 -- !query 13 output
-NULL
+23500000000
 
 
 -- !query 14
-select (-4e36 - 0.1) - 7e36
+select (5e36 + 0.1) + 5e36
 -- !query 14 schema
-struct<(CAST((CAST(-4E+36 AS DECIMAL(38,1)) - CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) - CAST(7E+36 AS DECIMAL(38,1))):decimal(38,1)>
+struct<(CAST((CAST(5E+36 AS DECIMAL(38,1)) + CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) + CAST(5E+36 AS DECIMAL(38,1))):decimal(38,1)>
 -- !query 14 output
 NULL
 
 
 -- !query 15
-select 12345678901234567890.0 * 12345678901234567890.0
+select (-4e36 - 0.1) - 7e36
 -- !query 15 schema
-struct<(12345678901234567890.0 * 12345678901234567890.0):decimal(38,2)>
+struct<(CAST((CAST(-4E+36 AS DECIMAL(38,1)) - CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) - CAST(7E+36 AS DECIMAL(38,1))):decimal(38,1)>
 -- !query 15 output
 NULL
 
 
 -- !query 16
-select 1e35 / 0.1
+select 12345678901234567890.0 * 12345678901234567890.0
 -- !query 16 schema
-struct<(CAST(1E+35 AS DECIMAL(37,1)) / CAST(0.1 AS DECIMAL(37,1))):decimal(38,6)>
+struct<(12345678901234567890.0 * 12345678901234567890.0):decimal(38,2)>
 -- !query 16 output
 NULL
 
 
 -- !query 17
-select 12345678912345678912345678912.1234567 + 9999999999999999999999999999999.12345
+select 1e35 / 0.1
 -- !query 17 schema
-struct<(CAST(12345678912345678912345678912.1234567 AS DECIMAL(38,6)) + CAST(9999999999999999999999999999999.12345 AS DECIMAL(38,6))):decimal(38,6)>
+struct<(CAST(1E+35 AS DECIMAL(37,1)) / CAST(0.1 AS DECIMAL(37,1))):decimal(38,6)>
 -- !query 17 output
-10012345678912345678912345678911.246907
+NULL
 
 
 -- !query 18
-select 123456789123456789.1234567890 * 1.123456789123456789
+select 1.2345678901234567890E30 * 1.2345678901234567890E25
 -- !query 18 schema
-struct<(CAST(123456789123456789.1234567890 AS DECIMAL(36,18)) * CAST(1.123456789123456789 AS DECIMAL(36,18))):decimal(38,18)>
+struct<(CAST(1.2345678901234567890E+30 AS DECIMAL(25,-6)) * CAST(1.2345678901234567890E+25 AS DECIMAL(25,-6))):decimal(38,-17)>
 -- !query 18 output
-138698367904130467.654320988515622621
+NULL
 
 
 -- !query 19
-select 12345678912345.123456789123 / 0.000000012345678
+select 12345678912345678912345678912.1234567 + 9999999999999999999999999999999.12345
 -- !query 19 schema
-struct<(CAST(12345678912345.123456789123 AS DECIMAL(29,15)) / CAST(1.2345678E-8 AS DECIMAL(29,15))):decimal(38,9)>
+struct<(CAST(12345678912345678912345678912.1234567 AS DECIMAL(38,6)) + CAST(9999999999999999999999999999999.12345 AS DECIMAL(38,6))):decimal(38,6)>
 -- !query 19 output
-1000000073899961059796.725866332
+10012345678912345678912345678911.246907
 
 
 -- !query 20
-set spark.sql.decimalOperations.allowPrecisionLoss=false
+select 123456789123456789.1234567890 * 1.123456789123456789
 -- !query 20 schema
-struct<key:string,value:string>
+struct<(CAST(123456789123456789.1234567890 AS DECIMAL(36,18)) * CAST(1.123456789123456789 AS DECIMAL(36,18))):decimal(38,18)>
 -- !query 20 output
-spark.sql.decimalOperations.allowPrecisionLoss	false
+138698367904130467.654320988515622621
 
 
 -- !query 21
-select id, a+b, a-b, a*b, a/b from decimals_test order by id
+select 12345678912345.123456789123 / 0.000000012345678
 -- !query 21 schema
-struct<id:int,(a + b):decimal(38,18),(a - b):decimal(38,18),(a * b):decimal(38,36),(a / b):decimal(38,18)>
+struct<(CAST(12345678912345.123456789123 AS DECIMAL(29,15)) / CAST(1.2345678E-8 AS DECIMAL(29,15))):decimal(38,9)>
 -- !query 21 output
-1	1099	-899	NULL	0.1001001001001001
-2	24690.246	0	NULL	1
-3	1234.2234567891011	-1233.9765432108989	NULL	0.000100037913541123
-4	123456789123456790.123456789123456789	123456789123456787.876543210876543211	NULL	109890109097814272.043109406191131436
+1000000073899961059796.725866332
 
 
 -- !query 22
-select id, a*10, b/10 from decimals_test order by id
+set spark.sql.decimalOperations.allowPrecisionLoss=false
 -- !query 22 schema
-struct<id:int,(CAST(a AS DECIMAL(38,18)) * CAST(CAST(10 AS DECIMAL(2,0)) AS DECIMAL(38,18))):decimal(38,18),(CAST(b AS DECIMAL(38,18)) / CAST(CAST(10 AS DECIMAL(2,0)) AS DECIMAL(38,18))):decimal(38,19)>
+struct<key:string,value:string>
 -- !query 22 output
-1	1000	99.9
-2	123451.23	1234.5123
-3	1.234567891011	123.41
-4	1234567891234567890	0.1123456789123456789
+spark.sql.decimalOperations.allowPrecisionLoss	false
 
 
 -- !query 23
-select 10.3 * 3.0
+select id, a+b, a-b, a*b, a/b from decimals_test order by id
 -- !query 23 schema
-struct<(CAST(10.3 AS DECIMAL(3,1)) * CAST(3.0 AS DECIMAL(3,1))):decimal(6,2)>
+struct<id:int,(a + b):decimal(38,18),(a - b):decimal(38,18),(a * b):decimal(38,36),(a / b):decimal(38,18)>
 -- !query 23 output
-30.9
+1	1099	-899	NULL	0.1001001001001001
+2	24690.246	0	NULL	1
+3	1234.2234567891011	-1233.9765432108989	NULL	0.000100037913541123
+4	123456789123456790.123456789123456789	123456789123456787.876543210876543211	NULL	109890109097814272.043109406191131436
 
 
 -- !query 24
-select 10.3000 * 3.0
+select id, a*10, b/10 from decimals_test order by id
 -- !query 24 schema
-struct<(CAST(10.3000 AS DECIMAL(6,4)) * CAST(3.0 AS DECIMAL(6,4))):decimal(9,5)>
+struct<id:int,(CAST(a AS DECIMAL(38,18)) * CAST(CAST(10 AS DECIMAL(2,0)) AS DECIMAL(38,18))):decimal(38,18),(CAST(b AS DECIMAL(38,18)) / CAST(CAST(10 AS DECIMAL(2,0)) AS DECIMAL(38,18))):decimal(38,19)>
 -- !query 24 output
-30.9
+1	1000	99.9
+2	123451.23	1234.5123
+3	1.234567891011	123.41
+4	1234567891234567890	0.1123456789123456789
 
 
 -- !query 25
-select 10.30000 * 30.0
+select 10.3 * 3.0
 -- !query 25 schema
-struct<(CAST(10.30000 AS DECIMAL(7,5)) * CAST(30.0 AS DECIMAL(7,5))):decimal(11,6)>
+struct<(CAST(10.3 AS DECIMAL(3,1)) * CAST(3.0 AS DECIMAL(3,1))):decimal(6,2)>
 -- !query 25 output
-309
+30.9
 
 
 -- !query 26
-select 10.300000000000000000 * 3.000000000000000000
+select 10.3000 * 3.0
 -- !query 26 schema
-struct<(CAST(10.300000000000000000 AS DECIMAL(20,18)) * CAST(3.000000000000000000 AS DECIMAL(20,18))):decimal(38,36)>
+struct<(CAST(10.3000 AS DECIMAL(6,4)) * CAST(3.0 AS DECIMAL(6,4))):decimal(9,5)>
 -- !query 26 output
 30.9
 
 
 -- !query 27
-select 10.300000000000000000 * 3.0000000000000000000
+select 10.30000 * 30.0
 -- !query 27 schema
-struct<(CAST(10.300000000000000000 AS DECIMAL(21,19)) * CAST(3.0000000000000000000 AS DECIMAL(21,19))):decimal(38,37)>
+struct<(CAST(10.30000 AS DECIMAL(7,5)) * CAST(30.0 AS DECIMAL(7,5))):decimal(11,6)>
 -- !query 27 output
-NULL
+309
 
 
 -- !query 28
-select (5e36 + 0.1) + 5e36
+select 10.300000000000000000 * 3.000000000000000000
 -- !query 28 schema
-struct<(CAST((CAST(5E+36 AS DECIMAL(38,1)) + CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) + CAST(5E+36 AS DECIMAL(38,1))):decimal(38,1)>
+struct<(CAST(10.300000000000000000 AS DECIMAL(20,18)) * CAST(3.000000000000000000 AS DECIMAL(20,18))):decimal(38,36)>
 -- !query 28 output
-NULL
+30.9
 
 
 -- !query 29
-select (-4e36 - 0.1) - 7e36
+select 10.300000000000000000 * 3.0000000000000000000
 -- !query 29 schema
-struct<(CAST((CAST(-4E+36 AS DECIMAL(38,1)) - CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) - CAST(7E+36 AS DECIMAL(38,1))):decimal(38,1)>
+struct<(CAST(10.300000000000000000 AS DECIMAL(21,19)) * CAST(3.0000000000000000000 AS DECIMAL(21,19))):decimal(38,37)>
 -- !query 29 output
 NULL
 
 
 -- !query 30
-select 12345678901234567890.0 * 12345678901234567890.0
+select 2.35E10 * 1.0
 -- !query 30 schema
-struct<(12345678901234567890.0 * 12345678901234567890.0):decimal(38,2)>
+struct<(CAST(2.35E+10 AS DECIMAL(12,1)) * CAST(1.0 AS DECIMAL(12,1))):decimal(6,-7)>
 -- !query 30 output
-NULL
+23500000000
 
 
 -- !query 31
-select 1e35 / 0.1
+select (5e36 + 0.1) + 5e36
 -- !query 31 schema
-struct<(CAST(1E+35 AS DECIMAL(37,1)) / CAST(0.1 AS DECIMAL(37,1))):decimal(38,3)>
+struct<(CAST((CAST(5E+36 AS DECIMAL(38,1)) + CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) + CAST(5E+36 AS DECIMAL(38,1))):decimal(38,1)>
 -- !query 31 output
 NULL
 
 
 -- !query 32
-select 12345678912345678912345678912.1234567 + 9999999999999999999999999999999.12345
+select (-4e36 - 0.1) - 7e36
 -- !query 32 schema
-struct<(CAST(12345678912345678912345678912.1234567 AS DECIMAL(38,7)) + CAST(9999999999999999999999999999999.12345 AS DECIMAL(38,7))):decimal(38,7)>
+struct<(CAST((CAST(-4E+36 AS DECIMAL(38,1)) - CAST(0.1 AS DECIMAL(38,1))) AS DECIMAL(38,1)) - CAST(7E+36 AS DECIMAL(38,1))):decimal(38,1)>
 -- !query 32 output
 NULL
 
 
 -- !query 33
-select 123456789123456789.1234567890 * 1.123456789123456789
+select 12345678901234567890.0 * 12345678901234567890.0
 -- !query 33 schema
-struct<(CAST(123456789123456789.1234567890 AS DECIMAL(36,18)) * CAST(1.123456789123456789 AS DECIMAL(36,18))):decimal(38,28)>
+struct<(12345678901234567890.0 * 12345678901234567890.0):decimal(38,2)>
 -- !query 33 output
 NULL
 
 
 -- !query 34
-select 12345678912345.123456789123 / 0.000000012345678
+select 1e35 / 0.1
 -- !query 34 schema
-struct<(CAST(12345678912345.123456789123 AS DECIMAL(29,15)) / CAST(1.2345678E-8 AS DECIMAL(29,15))):decimal(38,18)>
+struct<(CAST(1E+35 AS DECIMAL(37,1)) / CAST(0.1 AS DECIMAL(37,1))):decimal(38,3)>
 -- !query 34 output
 NULL
 
 
 -- !query 35
-drop table decimals_test
+select 1.2345678901234567890E30 * 1.2345678901234567890E25
 -- !query 35 schema
-struct<>
+struct<(CAST(1.2345678901234567890E+30 AS DECIMAL(25,-6)) * CAST(1.2345678901234567890E+25 AS DECIMAL(25,-6))):decimal(38,-17)>
 -- !query 35 output
+NULL
+
+
+-- !query 36
+select 12345678912345678912345678912.1234567 + 9999999999999999999999999999999.12345
+-- !query 36 schema
+struct<(CAST(12345678912345678912345678912.1234567 AS DECIMAL(38,7)) + CAST(9999999999999999999999999999999.12345 AS DECIMAL(38,7))):decimal(38,7)>
+-- !query 36 output
+NULL
+
+
+-- !query 37
+select 123456789123456789.1234567890 * 1.123456789123456789
+-- !query 37 schema
+struct<(CAST(123456789123456789.1234567890 AS DECIMAL(36,18)) * CAST(1.123456789123456789 AS DECIMAL(36,18))):decimal(38,28)>
+-- !query 37 output
+NULL
+
+
+-- !query 38
+select 12345678912345.123456789123 / 0.000000012345678
+-- !query 38 schema
+struct<(CAST(12345678912345.123456789123 AS DECIMAL(29,15)) / CAST(1.2345678E-8 AS DECIMAL(29,15))):decimal(38,18)>
+-- !query 38 output
+NULL
+
+
+-- !query 39
+drop table decimals_test
+-- !query 39 schema
+struct<>
+-- !query 39 output