GH-50225: [Ruby] Move merge implementation to ColumnContainable (#50226)

### Rationale for this change

`Arrow::Table#merge` and `Arrow::RecordBatch#merge` had similar implementations, resulting in duplicated merge logic.

### What changes are included in this PR?

This PR moves the common merge implementation to `Arrow::ColumnContainable`.

Container-specific behavior such as column conversion and creating the merged container remains implemented in `Arrow::Table` and `Arrow::RecordBatch`.

### Are these changes tested?

Yes.

The existing `RecordBatch` and `Table` test suites were run and passed successfully.

### Are there any user-facing changes?

No.
* GitHub Issue: #50225

Authored-by: Aaditya Srinivasan <aadityasri03@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>

Author: Reranko05

ruby/red-arrow/lib/arrow/column-containable.rb

@@ -152,5 +152,70 @@ def [](selector)
     def column_names
       @column_names ||= columns.collect(&:name)
     end
+
+    # Merges columns from the given container or Hash and creates
+    # a new container.
+    #
+    # @param other [Hash, self]
+    #   The columns to be merged.
+    #
+    # @return [self]
+    def merge(other)
+      added_columns = {}
+      removed_columns = {}
+
+      case other
+      when Hash
+        other.each do |name, value|
+          name = name.to_s
+          if value
+            added_columns[name] = ensure_raw_column(name, value)
+          else
+            removed_columns[name] = true
+          end
+        end
+      when self.class
+        other.columns.each do |column|
+          name = column.name
+          added_columns[name] = ensure_raw_column(name, column)
+        end
+      else
+        message = "merge target must be Hash or #{self.class}: " +
+          "<#{other.inspect}>: #{inspect}"
+        raise ArgumentError, message
+      end
+
+      new_columns = []
+
+      columns.each do |column|
+        column_name = column.name
+        new_column = added_columns.delete(column_name)
+
+        if new_column
+          new_columns << new_column
+          next
+        end
+
+        next if removed_columns.key?(column_name)
+
+        new_columns << ensure_raw_column(column_name, column)
+      end
+
+      added_columns.each_value do |new_column|
+        new_columns << new_column
+      end
+
+      new_fields = []
+      new_arrays = []
+
+      new_columns.each do |new_column|
+        new_fields << new_column[:field]
+        new_arrays << new_column[:data]
+      end
+
+      merged = self.class.new(new_fields, new_arrays)
+      share_input(merged)
+      merged
+    end
   end
 end

ruby/red-arrow/lib/arrow/record-batch.rb

@@ -37,7 +37,12 @@ def new(*args)
           super(schema, n_rows, values)
         when 2
           schema, data = args
-          RecordBatchBuilder.build(schema, data)
+          schema = Schema.new(schema) unless schema.is_a?(Schema)
+          if !data.empty? and data.all? {|array| array.is_a?(Arrow::Array)}
+            super(schema, data[0].size, data)
+          else
+            RecordBatchBuilder.build(schema, data)
+          end
         when 3
           super
         else
@@ -63,63 +68,6 @@ def to_table
       table
     end
 
-    def merge(other)
-      added_columns = {}
-      removed_columns = {}
-
-      case other
-      when Hash
-        other.each do |name, value|
-          name = name.to_s
-          if value
-            added_columns[name] = ensure_raw_column(name, value)
-          else
-            removed_columns[name] = true
-          end
-        end
-      when RecordBatch
-        other.columns.each do |column|
-          name = column.name
-          added_columns[name] = ensure_raw_column(name, column)
-        end
-      else
-        message = "merge target must be Hash or Arrow::RecordBatch: " +
-          "<#{other.inspect}>: #{inspect}"
-        raise ArgumentError, message
-      end
-
-      new_columns = []
-      columns.each do |column|
-        column_name = column.name
-        new_column = added_columns.delete(column_name)
-        if new_column
-          new_columns << new_column
-          next
-        end
-        next if removed_columns.key?(column_name)
-        new_columns << ensure_raw_column(column_name, column)
-      end
-
-      added_columns.each_value do |new_column|
-        new_columns << new_column
-      end
-
-      new_fields = []
-      new_arrays = []
-      new_columns.each do |new_column|
-        new_fields << new_column[:field]
-        new_arrays << new_column[:data]
-      end
-
-      record_batch = self.class.new(
-        Schema.new(new_fields),
-        n_rows,
-        new_arrays,
-      )
-      share_input(record_batch)
-      record_batch
-    end
-
     def respond_to_missing?(name, include_private)
       return true if find_column(name)
       super

ruby/red-arrow/lib/arrow/table.rb

@@ -354,60 +354,6 @@ def slice(*args)
       sliced_table
     end
 
-    # TODO
-    #
-    # @return [Arrow::Table]
-    def merge(other)
-      added_columns = {}
-      removed_columns = {}
-
-      case other
-      when Hash
-        other.each do |name, value|
-          name = name.to_s
-          if value
-            added_columns[name] = ensure_raw_column(name, value)
-          else
-            removed_columns[name] = true
-          end
-        end
-      when Table
-        added_columns = {}
-        other.columns.each do |column|
-          name = column.name
-          added_columns[name] = ensure_raw_column(name, column)
-        end
-      else
-        message = "merge target must be Hash or Arrow::Table: " +
-          "<#{other.inspect}>: #{inspect}"
-        raise ArgumentError, message
-      end
-
-      new_columns = []
-      columns.each do |column|
-        column_name = column.name
-        new_column = added_columns.delete(column_name)
-        if new_column
-          new_columns << new_column
-          next
-        end
-        next if removed_columns.key?(column_name)
-        new_columns << ensure_raw_column(column_name, column)
-      end
-      added_columns.each do |name, new_column|
-        new_columns << new_column
-      end
-      new_fields = []
-      new_arrays = []
-      new_columns.each do |new_column|
-        new_fields << new_column[:field]
-        new_arrays << new_column[:data]
-      end
-      table = self.class.new(new_fields, new_arrays)
-      share_input(table)
-      table
-    end
-
     alias_method :remove_column_raw, :remove_column
     def remove_column(name_or_index)
       case name_or_index