branch-2.1: [Fix](Nereids) fix floor/round/ceil/truncate functions type compute precision problem

fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/executable/NumericArithmetic.java

@@ -694,20 +694,25 @@ private static Expression checkOutputBoundary(Literal input) {
         return input;
     }
 
+    private static Expression castDecimalV3Literal(DecimalV3Literal literal, int precision) {
+        return new DecimalV3Literal(DecimalV3Type.createDecimalV3Type(precision, literal.getValue().scale()),
+                literal.getValue());
+    }
+
     /**
      * round
      */
     @ExecFunction(name = "round")
     public static Expression round(DecimalV3Literal first) {
-        return first.round(0);
+        return castDecimalV3Literal(first.round(0), first.getValue().precision());
     }
 
     /**
      * round
      */
     @ExecFunction(name = "round")
     public static Expression round(DecimalV3Literal first, IntegerLiteral second) {
-        return first.round(second.getValue());
+        return castDecimalV3Literal(first.round(second.getValue()), first.getValue().precision());
     }
 
     /**
@@ -733,15 +738,15 @@ public static Expression round(DoubleLiteral first, IntegerLiteral second) {
      */
     @ExecFunction(name = "ceil")
     public static Expression ceil(DecimalV3Literal first) {
-        return first.roundCeiling(0);
+        return castDecimalV3Literal(first.roundCeiling(0), first.getValue().precision());
     }
 
     /**
      * ceil
      */
     @ExecFunction(name = "ceil")
     public static Expression ceil(DecimalV3Literal first, IntegerLiteral second) {
-        return first.roundCeiling(second.getValue());
+        return castDecimalV3Literal(first.roundCeiling(second.getValue()), first.getValue().precision());
     }
 
     /**
@@ -767,15 +772,15 @@ public static Expression ceil(DoubleLiteral first, IntegerLiteral second) {
      */
     @ExecFunction(name = "floor")
     public static Expression floor(DecimalV3Literal first) {
-        return first.roundFloor(0);
+        return castDecimalV3Literal(first.roundFloor(0), first.getValue().precision());
     }
 
     /**
      * floor
      */
     @ExecFunction(name = "floor")
     public static Expression floor(DecimalV3Literal first, IntegerLiteral second) {
-        return first.roundFloor(second.getValue());
+        return castDecimalV3Literal(first.roundFloor(second.getValue()), first.getValue().precision());
     }
 
     /**
@@ -1136,21 +1141,10 @@ public static Expression mathE() {
     public static Expression truncate(DecimalV3Literal first, IntegerLiteral second) {
         if (first.getValue().compareTo(BigDecimal.ZERO) == 0) {
             return first;
+        } else if (first.getValue().compareTo(BigDecimal.ZERO) < 0) {
+            return castDecimalV3Literal(first.roundCeiling(second.getValue()), first.getValue().precision());
         } else {
-            if (first.getValue().scale() < second.getValue()) {
-                return first;
-            }
-            if (second.getValue() < 0) {
-                double factor = Math.pow(10, Math.abs(second.getValue()));
-                return new DecimalV3Literal(
-                    DecimalV3Type.createDecimalV3Type(first.getValue().precision(), 0),
-                    BigDecimal.valueOf(Math.floor(first.getDouble() / factor) * factor));
-            }
-            if (first.getValue().compareTo(BigDecimal.ZERO) == -1) {
-                return first.roundCeiling(second.getValue());
-            } else {
-                return first.roundFloor(second.getValue());
-            }
+            return castDecimalV3Literal(first.roundFloor(second.getValue()), first.getValue().precision());
         }
     }
 

regression-test/suites/nereids_p0/expression/fold_constant/fold_constant_numeric_arithmatic.groovy

@@ -409,4 +409,29 @@ test {
 
 //Additional cases for Xor, Conv, and other mathematical functions
     testFoldConst("SELECT CONV(-10, 10, 2) AS conv_invalid_base") //Conv with negative input (may be undefined)
+
+    // fix floor/ceil/round function return type with DecimalV3 input
+    testFoldConst("with cte as (select floor(300.343) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select round(300.343) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select ceil(300.343) order by 1 limit 1) select * from cte")
+
+    testFoldConst("with cte as (select floor(300.343, 2) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select round(300.343, 2) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select ceil(300.343, 2) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select truncate(300.343, 2) order by 1 limit 1) select * from cte")
+
+    testFoldConst("with cte as (select floor(300.343, 0) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select round(300.343, 0) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select ceil(300.343, 0) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select truncate(300.343, 0) order by 1 limit 1) select * from cte")
+
+    testFoldConst("with cte as (select floor(300.343, -1) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select round(300.343, -1) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select ceil(300.343, -1) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select truncate(300.343, -1) order by 1 limit 1) select * from cte")
+
+    testFoldConst("with cte as (select floor(300.343, -4) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select round(300.343, -4) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select ceil(300.343, -4) order by 1 limit 1) select * from cte")
+    testFoldConst("with cte as (select truncate(300.343, -4) order by 1 limit 1) select * from cte")
 }