[GitHub] [arrow] WillAyd commented on a diff in pull request #12963: ARROW-16234: [C++] Vector Kernel for Rank

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

WillAyd commented on code in PR #12963:
URL: https://github.com/apache/arrow/pull/12963#discussion_r863469841


##########
cpp/src/arrow/compute/kernels/vector_sort.cc:
##########
@@ -1909,6 +1909,110 @@ class SelectKUnstableMetaFunction : public MetaFunction {
   }
 };
 
+// ----------------------------------------------------------------------
+// Rank implementation
+
+const FunctionDoc rank_doc(
+    "Returns the ranking of an array",
+    ("This function computes a rank of the input array.\n"
+     "By default, Null values are considered greater than any other value and\n"
+     "are therefore sorted at the end of the input. For floating-point types,\n"
+     "NaNs are considered greater than any other non-null value, but smaller\n"
+     "than null values. The default tiebreaker is to assign ranks in order of\n"
+     "when ties appear in the input\n"
+     "\n"
+     "The handling of nulls, NaNs and tiebreakers can be changed in RankOptions."),
+    {"input"}, "RankOptions");
+
+class RankMetaFunction : public MetaFunction {
+ public:
+  RankMetaFunction()
+      : MetaFunction("rank", Arity::Unary(), &rank_doc, GetDefaultSortOptions()) {}
+
+  Result<Datum> ExecuteImpl(const std::vector<Datum>& args,
+                            const FunctionOptions* options, ExecContext* ctx) const {
+    const RankOptions& sort_options = static_cast<const RankOptions&>(*options);
+    switch (args[0].kind()) {
+      case Datum::ARRAY: {
+        return Rank(*args[0].make_array(), sort_options, ctx);
+      } break;
+      default:
+        break;
+    }
+    return Status::NotImplemented(
+        "Unsupported types for rank operation: "
+        "values=",
+        args[0].ToString());
+  }
+
+ private:
+  Result<Datum> Rank(const Array& array, const RankOptions& options,
+                     ExecContext* ctx) const {
+    ArraySortOptions array_options(options.order, options.null_placement);
+
+    ARROW_ASSIGN_OR_RAISE(auto sortIndices, CallFunction("array_sort_indices", {array},
+                                                         &array_options, ctx));

Review Comment:
   Figured out the error I had so was able to integrate this. Still need to clean up the code and integrate what you suggested with now having a null count at our disposal



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