replace hardcoding with type dispatch

Author: karthikeyann

velox/type/Type.cpp

@@ -119,6 +119,26 @@ std::string mapTypeKindToName(const TypeKind& typeKind) {
   return found->second;
 }
 
+namespace {
+template <TypeKind Kind>
+static int32_t kindSize() {
+  return sizeof(typename KindToFlatVector<Kind>::HashRowType);
+}
+
+static int32_t typeKindSize(TypeKind kind) {
+  if (kind == TypeKind::UNKNOWN) {
+    return sizeof(UnknownValue);
+  }
+
+  return VELOX_DYNAMIC_TYPE_DISPATCH(kindSize, kind);
+}
+} // namespace
+
+uint8_t getDecimalBitWidth(const Type& type) {
+    // Get the physical type's bit width
+    return typeKindSize(type.kind()) * 8;
+}
+
 std::pair<uint8_t, uint8_t> getDecimalPrecisionScale(const Type& type) {
   if (type.isShortDecimal()) {
     const auto& decimalType = static_cast<const ShortDecimalType&>(type);

velox/type/Type.h

@@ -845,6 +845,8 @@ FOLLY_ALWAYS_INLINE bool isDecimalName(const std::string& name) {
   return (name == "DECIMAL");
 }
 
+uint8_t getDecimalBitWidth(const Type& type);
+
 std::pair<uint8_t, uint8_t> getDecimalPrecisionScale(const Type& type);
 
 class UnknownType : public CanProvideCustomComparisonType<TypeKind::UNKNOWN> {

velox/vector/arrow/Bridge.cpp

@@ -259,30 +259,6 @@ const char* exportArrowFormatTimestampStr(
   return formatBuffer.c_str();
 }
 
-uint8_t getDecimalWidth(const Type& type) {
-    // Get the physical type's bit width
-    switch (type.kind()) {
-      case TypeKind::BOOLEAN:
-        return 1;
-      case TypeKind::TINYINT:
-        return 8;
-      case TypeKind::SMALLINT:
-        return 16;
-      case TypeKind::INTEGER:
-        return 32;
-      case TypeKind::BIGINT:
-        return 64;
-      case TypeKind::REAL:
-        return 32;
-      case TypeKind::DOUBLE:
-        return 64;
-      case TypeKind::HUGEINT:
-        return 128;
-      default:
-      return 0; // Default for complex types
-  }
-}
-
 // Returns the Arrow C data interface format type for a given Velox type.
 const char* exportArrowFormatStr(
     const TypePtr& type,
@@ -291,7 +267,7 @@ const char* exportArrowFormatStr(
   if (type->isDecimal()) {
     // Decimal types encode the precision, scale values.
     const auto& [precision, scale] = getDecimalPrecisionScale(*type);
-    auto const width = getDecimalWidth(*type);
+    auto const width = getDecimalBitWidth(*type);
     formatBuffer = fmt::format("d:{},{},{}", precision, scale, width);
     return formatBuffer.c_str();
   }