minni31 commented on code in PR #12777:
URL: https://github.com/apache/gluten/pull/12777#discussion_r4141112701


##########
gluten-substrait/src/main/scala/org/apache/gluten/expression/DecimalCeilFloorTransformer.scala:
##########
@@ -0,0 +1,63 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.gluten.expression
+
+import org.apache.gluten.backendsapi.BackendsApiManager
+import org.apache.gluten.exception.GlutenNotSupportException
+
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.types.{DataType, DecimalType}
+
+/**
+ * Transformer for Spark `RoundCeil(decimal, scale)` and `RoundFloor(decimal, 
scale)`. These power
+ * the 2-argument forms of `ceiling(x, scale)` / `floor(x, scale)` and 
dispatch to the Velox
+ * `decimal_ceil` / `decimal_floor` special forms (substrait names `ceil` / 
`floor`, remapped on the
+ * C++ side based on arity + decimal arg type).
+ *
+ * The output `DataType` is recomputed from the original Spark decimal input 
type and the constant
+ * folded scale, matching Spark's `RoundBase.dataType` formula. Mirrors the 
structure of
+ * `DecimalRoundTransformer`.
+ */
+case class DecimalCeilFloorTransformer(
+    substraitExprName: String,
+    child: ExpressionTransformer,
+    original: Expression,
+    scaleExpr: Expression)
+  extends BinaryExpressionTransformer {
+
+  private val toScale: Int = {
+    val evaluated = scaleExpr.eval(EmptyRow)
+    if (evaluated == null) {
+      throw new GlutenNotSupportException(
+        s"Scale expression evaluated to null for ${original.nodeName}. Falling 
back to Spark.")
+    }
+    evaluated.asInstanceOf[Int]
+  }

Review Comment:
   Fixed in 7c1830872. The transformer now requires a foldable scale and 
converts evaluation failures, null results, and unexpected result types into 
`GlutenNotSupportException`, so unsupported scale expressions fall back cleanly 
instead of aborting transformation.



##########
backends-velox/src/test/scala/org/apache/gluten/functions/MathFunctionsValidateSuite.scala:
##########
@@ -122,6 +122,30 @@ class MathFunctionsValidateSuite extends 
FunctionsValidateSuite {
     }
   }
 
+  test("2-arg ceiling / floor on decimals (RoundCeil / RoundFloor)") {
+    // The 2-arg forms produce Spark RoundCeil / RoundFloor and dispatch to 
the Velox
+    // decimal_ceil / decimal_floor special forms. The projection is native 
only when the
+    // expression offloads, so checkGlutenPlan[ProjectExecTransformer] doubles 
as an offload
+    // assertion; runQueryAndCompare additionally validates results against 
vanilla Spark.

Review Comment:
   Rechecked this against the supported Spark binaries while addressing the 
review. Spark 3.4/3.5 already register the two-argument 
`ceil`/`ceiling`/`floor` builders and construct `RoundCeil`/`RoundFloor` (the 
overload predates Spark 4.0). In 7c1830872, I removed the incorrect 
Spark-4-only gate so these tests now run across all supported profiles.



##########
cpp/velox/substrait/SubstraitParser.cc:
##########
@@ -287,6 +287,13 @@ std::string SubstraitParser::mapToVeloxFunction(const 
std::string& substraitFunc
     if (substraitFunction == "round") {
       return "decimal_round";
     }
+    // Spark RoundCeil / RoundFloor are emitted with substrait names "ceil"
+    // and "floor" but require dispatch to the 2-arg decimal special forms.
+    // The unary forms `ceil(decimal)` / `floor(decimal)` keep their original
+    // name (handled by simple-function registration).
+    if (numArgs == 2 && (substraitFunction == "ceil" || substraitFunction == 
"floor")) {
+      return "decimal_" + substraitFunction;

Review Comment:
   Fixed in 7c1830872. Overflow-prone decimal directional rounding now falls 
back to Spark whenever rounding can exceed the capped precision, regardless of 
ANSI mode. The regression coverage checks both `ceiling` and `floor`, ANSI on 
and off, the scale -38 threshold, and the `Int.MinValue` scale boundary.



##########
gluten-substrait/src/main/scala/org/apache/gluten/expression/ExpressionConverter.scala:
##########
@@ -390,6 +390,18 @@ object ExpressionConverter extends SQLConfHelper with 
Logging {
           substraitExprName,
           replaceWithExpressionTransformer0(r.child, attributeSeq, 
expressionsMap),
           r)
+      case rc: RoundCeil if rc.child.dataType.isInstanceOf[DecimalType] =>

Review Comment:
   Verified while fixing the review: `RoundCeil` and `RoundFloor` are present 
in the Spark 3.4 and 3.5 Catalyst APIs and are already exercised by the 
version-specific Spark expression suites. The common converter therefore 
remains version-compatible; 7c1830872 also runs the SQL coverage on all 
supported Spark profiles instead of gating it to Spark 4.x.



##########
backends-velox/src/test/scala/org/apache/gluten/functions/MathFunctionsValidateSuite.scala:
##########
@@ -122,6 +123,51 @@ class MathFunctionsValidateSuite extends 
FunctionsValidateSuite {
     }
   }
 
+  test("2-arg ceiling / floor on decimals (RoundCeil / RoundFloor)") {
+    // The 2-argument ceiling/floor SQL forms only exist on Spark 4.0+; on 
Spark 3.4/3.5 they are
+    // invalid and would fail during analysis, so skip the test on those 
profiles.
+    assume(SparkVersionUtil.gteSpark40)
+    // The 2-arg forms produce Spark RoundCeil / RoundFloor and dispatch to 
the Velox
+    // decimal_ceil / decimal_floor special forms. The projection is native 
only when the
+    // expression offloads, so checkGlutenPlan[ProjectExecTransformer] doubles 
as an offload
+    // assertion; runQueryAndCompare additionally validates results against 
vanilla Spark.
+    runQueryAndCompare(
+      "SELECT ceiling(cast(l_quantity as decimal(12, 2)), 1) FROM lineitem 
limit 10") {
+      checkGlutenPlan[ProjectExecTransformer]
+    }
+    runQueryAndCompare(
+      "SELECT floor(cast(l_quantity as decimal(12, 2)), 1) FROM lineitem limit 
10") {
+      checkGlutenPlan[ProjectExecTransformer]
+    }
+    // Negative scale rounds to the left of the decimal point.
+    runQueryAndCompare(
+      "SELECT ceiling(cast(l_extendedprice as decimal(20, 4)), -2) FROM 
lineitem limit 10") {
+      checkGlutenPlan[ProjectExecTransformer]
+    }
+    runQueryAndCompare(
+      "SELECT floor(cast(l_extendedprice as decimal(20, 4)), -2) FROM lineitem 
limit 10") {
+      checkGlutenPlan[ProjectExecTransformer]
+    }
+  }
+
+  test("2-arg ceiling / floor on decimals falls back under ANSI overflow") {
+    assume(SparkVersionUtil.gteSpark40)
+    // Velox's decimal_ceil / decimal_floor return NULL when the rounded 
result overflows the
+    // declared precision, whereas Spark raises under ANSI mode. Even with 
ANSI fallback disabled
+    // (native ANSI execution opted in), this op must fall back to Spark so 
the overflow raises
+    // instead of silently producing NULL. DECIMAL(38, 0) at its maximum value 
rounded with a
+    // negative scale overflows the 38-digit output precision.
+    withSQLConf(
+      SQLConf.ANSI_ENABLED.key -> "true",
+      GlutenConfig.GLUTEN_ANSI_FALLBACK_ENABLED.key -> "false") {
+      val overflowSql =
+        "SELECT ceiling(cast('99999999999999999999999999999999999999' as 
decimal(38, 0)), -1)"
+      intercept[Exception] {
+        spark.sql(overflowSql).collect()
+      }

Review Comment:
   Fixed in 7c1830872. The overflow tests now inspect the executed plan and 
require `ProjectExecTransformer` to be absent, then assert that the thrown 
exception is an arithmetic overflow (directly or through its cause chain). This 
distinguishes genuine Spark fallback/overflow behavior from an arbitrary 
planning exception.



##########
backends-velox/src/test/scala/org/apache/gluten/functions/MathFunctionsValidateSuite.scala:
##########
@@ -122,6 +123,51 @@ class MathFunctionsValidateSuite extends 
FunctionsValidateSuite {
     }
   }
 
+  test("2-arg ceiling / floor on decimals (RoundCeil / RoundFloor)") {
+    // The 2-argument ceiling/floor SQL forms only exist on Spark 4.0+; on 
Spark 3.4/3.5 they are
+    // invalid and would fail during analysis, so skip the test on those 
profiles.
+    assume(SparkVersionUtil.gteSpark40)

Review Comment:
   Fixed in 7c1830872. The normal native-offload comparisons now run explicitly 
with ANSI disabled. Separate coverage enables ANSI with 
`spark.gluten.sql.ansiFallback.enabled=false` and verifies that precision-safe 
decimal ceiling/floor expressions still offload natively.



##########
gluten-substrait/src/main/scala/org/apache/gluten/expression/DecimalCeilFloorTransformer.scala:
##########
@@ -0,0 +1,96 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.gluten.expression
+
+import org.apache.gluten.backendsapi.BackendsApiManager
+import org.apache.gluten.exception.GlutenNotSupportException
+
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.internal.SQLConf
+import org.apache.spark.sql.types.{DataType, DecimalType}
+
+/**
+ * Transformer for Spark `RoundCeil(decimal, scale)` and `RoundFloor(decimal, 
scale)`. These power
+ * the 2-argument forms of `ceiling(x, scale)` / `floor(x, scale)` and 
dispatch to the Velox
+ * `decimal_ceil` / `decimal_floor` special forms (substrait names `ceil` / 
`floor`, remapped on the
+ * C++ side based on arity + decimal arg type).
+ *
+ * The output `DataType` is recomputed from the original Spark decimal input 
type and the constant
+ * folded scale, matching Spark's `RoundBase.dataType` formula. Mirrors the 
structure of
+ * `DecimalRoundTransformer`.
+ */
+case class DecimalCeilFloorTransformer(
+    substraitExprName: String,
+    child: ExpressionTransformer,
+    original: Expression,
+    scaleExpr: Expression)
+  extends BinaryExpressionTransformer {
+
+  // Velox's `decimal_ceil` / `decimal_floor` return NULL when the rounded 
result exceeds the
+  // declared decimal precision, whereas Spark's `RoundBase` raises a 
precision-overflow error
+  // under ANSI mode (e.g. DECIMAL(38, 0) at its maximum value rounded with a 
negative scale).
+  // Offloading under ANSI would silently substitute NULL for that error, so 
fall back to vanilla
+  // Spark and preserve the ANSI semantics. Under non-ANSI mode Spark also 
returns NULL on
+  // overflow, matching Velox, so offloading is safe.
+  if (SQLConf.get.ansiEnabled) {
+    throw new GlutenNotSupportException(
+      s"${original.nodeName} on decimal is not offloaded under ANSI mode 
because Velox returns " +
+        "NULL on precision overflow while Spark raises. Falling back to 
Spark.")

Review Comment:
   Fixed in 7c1830872. The blanket ANSI rejection was replaced with a selective 
type-level guard: fallback occurs only when rounding can change the value and 
the uncapped output precision exceeds Spark's maximum. Safe ANSI cases, 
including no-op `DECIMAL(38, s)` cases, remain eligible for native execution. 
Unsupported negative-input-scale decimals also fall back explicitly because 
Velox cannot represent them safely.



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