[GitHub] [arrow] wesm commented on a change in pull request #7612: ARROW-7011: [C++] Implement casts from float/double to decimal

[GitBox <gi...@apache.org>]

wesm commented on a change in pull request #7612:
URL: https://github.com/apache/arrow/pull/7612#discussion_r449248816



##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_numeric.cc
##########
@@ -467,6 +467,51 @@ struct CastFunctor<Decimal128Type, Decimal128Type> {
   }
 };
 
+// ----------------------------------------------------------------------
+// Real to decimal
+
+template <bool AllowTruncate>
+struct RealToDecimal {
+  template <typename OUT, typename RealType>
+  Decimal128 Call(KernelContext* ctx, RealType val) const {
+    auto result = Decimal128::FromReal(val, out_precision_, out_scale_);
+    if (ARROW_PREDICT_FALSE(!result.ok())) {
+      if (!AllowTruncate) {
+        ctx->SetStatus(result.status());
+      }
+      return Decimal128();  // Zero
+    } else {
+      return *std::move(result);
+    }
+  }
+
+  int32_t out_scale_, out_precision_;
+};
+
+using SafeRealToDecimal = RealToDecimal<true>;
+using UnsafeRealToDecimal = RealToDecimal<false>;

Review comment:
       I'm not sure the performance benefit of pruning the `AllowTruncate` branch merits the 2x code size -- what do you think about making this flag just a member of the functor?




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