[GitHub] [arrow] lidavidm commented on a diff in pull request #34406: GH-34405: [C++] Add support for custom names in QueryOptions. Wire this up to Substrait

["lidavidm (via GitHub)" <gi...@apache.org>]

lidavidm commented on code in PR #34406:
URL: https://github.com/apache/arrow/pull/34406#discussion_r1126828055


##########
cpp/src/arrow/compute/exec/options.h:
##########
@@ -614,6 +616,13 @@ class ARROW_EXPORT TableSinkNodeOptions : public ExecNodeOptions {
   ///
   /// \see QueryOptions for more details
   std::optional<bool> sequence_output;
+  /// \brief Custom names to use for the columns.
+  ///
+  /// If specified then names must be provided for all fields. Currently, only a flat
+  /// schema is supported (see ARROW-15901).

Review Comment:
   nit: maybe we should refer to the GitHub issue instead? (I assume this was copied from above)



##########
cpp/src/arrow/compute/exec/exec_plan.cc:
##########
@@ -925,14 +943,32 @@ struct BatchConverter {
         });
   }
 
+  Result<std::shared_ptr<Schema>> InitializeSchema(
+      const std::vector<std::string>& names) {
+    // By this point this->schema will have been set by the SinkNode.  We potentially
+    // rename it with the names provided by the user and then return this in case the user
+    // wants to know the output schema.
+    if (!names.empty()) {
+      if (static_cast<int>(names.size()) != schema->num_fields()) {
+        return Status::Invalid(
+            "A plan was created with custom field names but the number of names did not "
+            "match the number of output columns");

Review Comment:
   nit: include expected/actual count in the message for convenience?



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