feat: add decimal argument support to round function

extensions/functions_rounding_decimal.yaml

@@ -0,0 +1,80 @@
+%YAML 1.2
+---
+scalar_functions:
+  -
+    name: "ceil"
+    description: >
+      Rounding to the ceiling of the value `x`.
+    impls:
+      - args:
+          - value: decimal<P,S>
+            name: x
+        return: |-
+          integral_least_num_digits = P - S + 1
+          precision = min(integral_least_num_digits, 38)
+          decimal?<precision, 0>
+  -
+    name: "floor"
+    description: >
+      Rounding to the floor of the value `x`.
+    impls:
+      - args:
+          - value: decimal<P,S>
+            name: x
+        return: |-
+          integral_least_num_digits = P - S + 1
+          precision = min(integral_least_num_digits, 38)
+          decimal?<precision, 0>
+  -
+    name: "round"
+    description: >
+      Rounding the value `x` to `s` decimal places.
+    impls:
+      - args:
+          - value: decimal<P1,S1>
+            name: x
+            description: >
+              Numerical expression to be rounded.
+          - value: i32
+            name: s
+            description: >
+              Number of decimal places to be rounded to.
+
+              When `s` is a positive number, the rounding
+              is performed to a `s` number of decimal places.
+
+              When `s` is a negative number, the rounding is
+              performed to the left side of the decimal point
+              as specified by `s`.
+
+              The precision and scale of the resultant decimal
+              type will be adjusted from the input decimal type
+              dependent on the value of `s`.
+        options:
+          rounding:
+            description: >
+              When a boundary is computed to lie somewhere between two values,
+              and this value cannot be exactly represented, this specifies how
+              to round it.
+
+                - TIE_TO_EVEN: round to nearest value; if exactly halfway, tie
+                  to the even option.
+                - TIE_AWAY_FROM_ZERO: round to nearest value; if exactly
+                  halfway, tie away from zero.
+                - TRUNCATE: always round toward zero.
+                - CEILING: always round toward positive infinity.
+                - FLOOR: always round toward negative infinity.
+                - AWAY_FROM_ZERO: round negative values with FLOOR rule, round positive values with CEILING rule
+                - TIE_DOWN: round ties with FLOOR rule
+                - TIE_UP: round ties with CEILING rule
+                - TIE_TOWARDS_ZERO: round ties with TRUNCATE rule
+                - TIE_TO_ODD: round to nearest value; if exactly halfway, tie
+                  to the odd option.
+            values: [ TIE_TO_EVEN, TIE_AWAY_FROM_ZERO, TRUNCATE, CEILING, FLOOR,
+              AWAY_FROM_ZERO, TIE_DOWN, TIE_UP, TIE_TOWARDS_ZERO, TIE_TO_ODD ]
+        nullability: DECLARED_OUTPUT
+        return: |-
+          integral_digits = P1 - S1 + 1
+          scale = s > 0 ? min(s, S1) : 0
+          precision = s > 0 ? min(integral_digits + scale, 38) : min(max(integral_num_digits, 1- s), 38)
+          decimal?<precision, scale>

tests/cases/rounding_decimal/ceil_decimal.test

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+### SUBSTRAIT_SCALAR_TEST: v1.0
+### SUBSTRAIT_INCLUDE: '/extensions/functions_rounding_decimal.yaml'
+
+# basic: Basic examples without any special cases
+ceil(2.25::dec<8,2>) = 3::dec<7,0>
+ceil(-65.5::dec<8,2>) = -65::dec<7,0>
+ceil(9.9::dec<2,1>) = 10::dec<2,0>

tests/cases/rounding_decimal/floor_decimal.test

@@ -0,0 +1,6 @@
+### SUBSTRAIT_SCALAR_TEST: v1.0
+### SUBSTRAIT_INCLUDE: '/extensions/functions_rounding_decimal.yaml'
+
+# basic: Basic examples without any special cases
+floor(2.25::dec<8,2>) = 2::dec<7,0>
+floor(-65.5::dec<8,2>) = -66::dec<7,0>

tests/cases/rounding_decimal/round_decimal.test

@@ -0,0 +1,11 @@
+### SUBSTRAIT_SCALAR_TEST: v1.0
+### SUBSTRAIT_INCLUDE: '/extensions/functions_rounding_decimal.yaml'
+
+# basic: Basic examples without any special cases
+round(2::dec<2,0>, 2::i32) = 2::dec<3,0>
+round(2.75::dec<8,2>, 1::i32) = 2.8::dec<8,1>
+
+# negative_rounding: Examples with negative rounding
+round(2::dec<2,0>, -2::i32) = 0::dec<2,0>
+round(123::dec<2,0>, -2::i32) = 100::dec<2,0>
+round(8793::dec<2,0>, -2::i32) = 8800::dec<2,0>