SQL: Fix result column names for CAST (#33604)

Previously, when an non-pruned cast (casting as a different
data type) got applied on a table column in the `SELECT` clause,
the name of the result column didn't contain the target data type
of the cast, e.g.:

  SELECT CAST(MAX(salary) AS DOUBLE) FROM "test_emp"

returned as column name:

  CAST(MAX(salary))

instead of:

  CAST(MAX(salary) AS DOUBLE)

Closes #33571

* Added more tests for trivial casts that are pruned

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/Cast.java

@@ -111,4 +111,11 @@ public class Cast extends UnaryScalarFunction {
     public String toString() {
         return functionName() + "(" + field().toString() + " AS " + to().sqlName() + ")#" + id();
     }
-}
+
+    @Override
+    public String name() {
+        StringBuilder sb = new StringBuilder(super.name());
+        sb.insert(sb.length() - 1, " AS " + to().sqlName());
+        return sb.toString();
+    }
+}

x-pack/qa/sql/src/main/resources/agg.csv-spec

@@ -74,6 +74,30 @@ SELECT SUM(salary) FROM test_emp;
 4824855
 ;
 
+aggregateWithCastPruned
+SELECT CAST(SUM(salary) AS INTEGER) FROM test_emp;
+
+  SUM(salary)
+-------------
+4824855
+;
+
+aggregateWithUpCast
+SELECT CAST(SUM(salary) AS DOUBLE) FROM test_emp;
+
+  CAST(SUM(salary) AS DOUBLE)
+-----------------------------
+4824855.0
+;
+
+aggregateWithCastNumericToString
+SELECT CAST(AVG(salary) AS VARCHAR) FROM test_emp;
+
+  CAST(AVG(salary) AS VARCHAR):s
+--------------------------------
+48248.55
+;
+
 kurtosisAndSkewnessNoGroup
 SELECT KURTOSIS(emp_no) k, SKEWNESS(salary) s FROM test_emp;
 

x-pack/qa/sql/src/main/resources/agg.sql-spec

@@ -90,6 +90,10 @@ aggCountImplicit
 SELECT COUNT(*) AS count FROM test_emp;
 aggCountImplicitWithCast
 SELECT CAST(COUNT(*) AS INT) c FROM "test_emp";
+aggCountImplicitWithUpCast
+SELECT CAST(COUNT(*) AS DOUBLE) c FROM "test_emp";
+aggCountImplicitWithPrunedCast
+SELECT CAST(COUNT(*) AS BIGINT) c FROM "test_emp";
 aggCountImplicitWithConstant
 SELECT COUNT(1) FROM "test_emp";
 aggCountImplicitWithConstantAndFilter
@@ -184,6 +188,10 @@ SELECT MIN(emp_no) AS min FROM test_emp;
 // end::min
 aggMinImplicitWithCast
 SELECT CAST(MIN(emp_no) AS SMALLINT) m FROM "test_emp";
+aggMinImplicitWithUpCast
+SELECT CAST(MIN(emp_no) AS DOUBLE) m FROM "test_emp";
+aggMinImplicitWithPrunedCast
+SELECT CAST(MIN(emp_no) AS INTEGER) m FROM "test_emp";
 aggMin
 SELECT gender g, MIN(emp_no) m FROM "test_emp" GROUP BY gender ORDER BY gender;
 aggMinWithCast
@@ -236,6 +244,10 @@ aggMaxImplicit
 SELECT MAX(salary) AS max FROM test_emp;
 aggMaxImplicitWithCast
 SELECT CAST(MAX(emp_no) AS SMALLINT) c FROM "test_emp";
+aggMaxImplicitWithUpCast
+SELECT CAST(MAX(emp_no) AS DOUBLE) c FROM "test_emp";
+aggMaxImplicitWithPrunedCast
+SELECT CAST(MAX(emp_no) AS INTEGER) c FROM "test_emp";
 aggMax
 SELECT gender g, MAX(emp_no) m FROM "test_emp" GROUP BY gender ORDER BY gender;
 aggMaxWithCast
@@ -268,6 +280,10 @@ SELECT gender g, MAX(emp_no) m FROM "test_emp" GROUP BY g HAVING m > 10 AND MAX(
 // SUM
 aggSumImplicitWithCast
 SELECT CAST(SUM(emp_no) AS BIGINT) s FROM "test_emp";
+aggSumImplicitWithUpCast
+SELECT CAST(SUM(emp_no) AS DOUBLE) s FROM "test_emp";
+aggSumImplicitWithUpCast
+SELECT CAST(SUM(emp_no) AS INTEGER) s FROM "test_emp";
 aggSumWithCast
 SELECT gender g, CAST(SUM(emp_no) AS BIGINT) s FROM "test_emp" GROUP BY gender ORDER BY gender;
 aggSumWithCastAndCount
@@ -298,6 +314,8 @@ SELECT gender g, CAST(SUM(emp_no) AS INT) s FROM "test_emp" GROUP BY g HAVING s
 // AVG
 aggAvgImplicitWithCast
 SELECT CAST(AVG(emp_no) AS FLOAT) a FROM "test_emp";
+aggAvgImplicitWithUpCast
+SELECT CAST(AVG(emp_no) AS DOUBLE) a FROM "test_emp";
 aggAvgWithCastToFloat
 SELECT gender g, CAST(AVG(emp_no) AS FLOAT) a FROM "test_emp" GROUP BY gender ORDER BY gender;
 // casting to an exact type - varchar, bigint, etc... will likely fail due to rounding error