support allowDecimalPrecisionLoss

Signed-off-by: Yuan Zhou <[email protected]>

Author: zhouyuan

cpp/core/config/GlutenConfig.h

@@ -34,6 +34,8 @@ const std::string kLegacySize = "spark.sql.legacy.sizeOfNull";
 
 const std::string kSessionTimezone = "spark.sql.session.timeZone";
 
+const std::string kAllowPrecisionLoss = "spark.sql.decimalOperations.allowPrecisionLoss";
+
 const std::string kIgnoreMissingFiles = "spark.sql.files.ignoreMissingFiles";
 
 const std::string kDefaultSessionTimezone = "spark.gluten.sql.session.timeZone.default";

cpp/velox/compute/WholeStageResultIterator.cc

@@ -490,6 +490,8 @@ std::unordered_map<std::string, std::string> WholeStageResultIterator::getQueryC
     }
     // Adjust timestamp according to the above configured session timezone.
     configs[velox::core::QueryConfig::kAdjustTimestampToTimezone] = "true";
+    // To align with Spark's behavior, allow decimal precision loss or not.
+    configs[velox::core::QueryConfig::kAllowPrecisionLoss] = veloxCfg_->get<std::string>(kAllowPrecisionLoss, "true");
     // Align Velox size function with Spark.
     configs[velox::core::QueryConfig::kSparkLegacySizeOfNull] = std::to_string(veloxCfg_->get<bool>(kLegacySize, true));
 

ep/build-velox/src/get_velox.sh

@@ -16,8 +16,8 @@
 
 set -exu
 
-VELOX_REPO=https://github.com/oap-project/velox.git
-VELOX_BRANCH=2024_05_06
+VELOX_REPO=https://github.com/zhouyuan/velox.git
+VELOX_BRANCH=wip_decimal_precision_loss
 VELOX_HOME=""
 
 #Set on run gluten on HDFS

gluten-core/src/main/scala/org/apache/gluten/expression/ExpressionConverter.scala

@@ -511,14 +511,6 @@ object ExpressionConverter extends SQLConfHelper with Logging {
             replaceWithExpressionTransformerInternal(_, attributeSeq, expressionsMap)),
           expr)
       case b: BinaryArithmetic if DecimalArithmeticUtil.isDecimalArithmetic(b) =>
-        // PrecisionLoss=true: velox support / ch not support
-        // PrecisionLoss=false: velox not support / ch support
-        // TODO ch support PrecisionLoss=true
-        if (!BackendsApiManager.getSettings.allowDecimalArithmetic) {
-          throw new GlutenNotSupportException(
-            s"Not support ${SQLConf.DECIMAL_OPERATIONS_ALLOW_PREC_LOSS.key} " +
-              s"${conf.decimalOperationsAllowPrecisionLoss} mode")
-        }
         val rescaleBinary = if (BackendsApiManager.getSettings.rescaleDecimalLiteral) {
           DecimalArithmeticUtil.rescaleLiteral(b)
         } else {

gluten-core/src/main/scala/org/apache/gluten/utils/DecimalArithmeticUtil.scala

@@ -22,6 +22,7 @@ import org.apache.gluten.expression.{CheckOverflowTransformer, ChildTransformer,
 
 import org.apache.spark.sql.catalyst.analysis.DecimalPrecision
 import org.apache.spark.sql.catalyst.expressions.{Add, BinaryArithmetic, Cast, Divide, Expression, Literal, Multiply, Pmod, PromotePrecision, Remainder, Subtract}
+import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types.{ByteType, Decimal, DecimalType, IntegerType, LongType, ShortType}
 
 object DecimalArithmeticUtil {
@@ -33,12 +34,14 @@ object DecimalArithmeticUtil {
 
   val MIN_ADJUSTED_SCALE = 6
   val MAX_PRECISION = 38
+  val MAX_SCALE = 38
 
   // Returns the result decimal type of a decimal arithmetic computing.
   def getResultTypeForOperation(
       operationType: OperationType.Config,
       type1: DecimalType,
       type2: DecimalType): DecimalType = {
+    val allowPrecisionLoss = SQLConf.get.decimalOperationsAllowPrecisionLoss
     var resultScale = 0
     var resultPrecision = 0
     operationType match {
@@ -54,16 +57,32 @@ object DecimalArithmeticUtil {
         resultScale = type1.scale + type2.scale
         resultPrecision = type1.precision + type2.precision + 1
       case OperationType.DIVIDE =>
-        resultScale = Math.max(MIN_ADJUSTED_SCALE, type1.scale + type2.precision + 1)
-        resultPrecision = type1.precision - type1.scale + type2.scale + resultScale
+        if (allowPrecisionLoss) {
+          resultScale = Math.max(MIN_ADJUSTED_SCALE, type1.scale + type2.precision + 1)
+          resultPrecision = type1.precision - type1.scale + type2.scale + resultScale
+        } else {
+          var intDig = Math.min(MAX_SCALE, type1.precision - type1.scale + type2.scale)
+          var decDig = Math.min(MAX_SCALE, Math.max(6, type1.scale + type2.precision + 1))
+          val diff = (intDig + decDig) - MAX_SCALE
+          if (diff > 0) {
+            decDig -= diff / 2 + 1
+            intDig = MAX_SCALE - decDig
+          }
+          resultScale = intDig + decDig
+          resultPrecision = decDig
+        }
       case OperationType.MOD =>
         resultScale = Math.max(type1.scale, type2.scale)
         resultPrecision =
           Math.min(type1.precision - type1.scale, type2.precision - type2.scale + resultScale)
       case other =>
         throw new GlutenNotSupportException(s"$other is not supported.")
     }
-    adjustScaleIfNeeded(resultPrecision, resultScale)
+    if (allowPrecisionLoss) {
+      adjustScaleIfNeeded(resultPrecision, resultScale)
+    } else {
+      bounded(resultPrecision, resultScale)
+    }
   }
 
   // Returns the adjusted decimal type when the precision is larger the maximum.
@@ -79,6 +98,10 @@ object DecimalArithmeticUtil {
     DecimalType(typePrecision, typeScale)
   }
 
+  def bounded(precision: Int, scale: Int): DecimalType = {
+    DecimalType(Math.min(precision, MAX_PRECISION), Math.min(scale, MAX_SCALE))
+  }
+
   // If casting between DecimalType, unnecessary cast is skipped to avoid data loss,
   // because argument input type of "cast" is actually the res type of "+-*/".
   // Cast will use a wider input type, then calculates result type with less scale than expected.

shims/common/src/main/scala/org/apache/gluten/GlutenConfig.scala

@@ -571,6 +571,7 @@ object GlutenConfig {
       GLUTEN_DEFAULT_SESSION_TIMEZONE_KEY,
       SQLConf.LEGACY_SIZE_OF_NULL.key,
       "spark.io.compression.codec",
+      "spark.sql.decimalOperations.allowPrecisionLoss",
       COLUMNAR_VELOX_BLOOM_FILTER_EXPECTED_NUM_ITEMS.key,
       COLUMNAR_VELOX_BLOOM_FILTER_NUM_BITS.key,
       COLUMNAR_VELOX_BLOOM_FILTER_MAX_NUM_BITS.key,