wave8b: 438/196 — rails-0017, hanami-0001, spark-0002 + PDF

defects/rails/patch/rails-0017-rename-column-indexes-set.patch

@@ -0,0 +1,39 @@
+--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
++++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+@@ -1459,10 +1459,11 @@ module ActiveRecord
+       def rename_column_indexes(table_name, column_name, new_column_name)
+         column_name, new_column_name = column_name.to_s, new_column_name.to_s
+         indexes(table_name).each do |index|
+-          next unless index.columns.include?(new_column_name)
++          col_set = index.columns.is_a?(Array) ? index.columns.to_set : index.columns
++          next unless col_set.include?(new_column_name)
+           old_columns = index.columns.dup
+-          old_columns[old_columns.index(new_column_name)] = column_name
++          old_columns[old_columns.index(new_column_name)] = column_name  # Array#index OK: called once per index, not in inner loop
+           generated_index_name = index_name(table_name, column: old_columns)
+           if generated_index_name == index.name
+             rename_index table_name, generated_index_name, index_name(table_name, column: index.columns)
+
+# CWE-407: Algorithmic Complexity — O(I×C) → O(I) for rename_column_indexes
+#
+# Defect ID : rails-0017
+# File      : activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+# Method    : rename_column_indexes (private)
+# Severity  : MEDIUM
+#
+# Pattern:
+#   indexes(table_name).each do |index|          # outer loop: I indexes
+#     next unless index.columns.include?(...)     # Array#include? — O(C) linear scan
+#
+# `index.columns` is a plain Array (e.g. ["user_id", "created_at"]).
+# For each of the I indexes, `include?` scans all C column names: O(I×C) total.
+# In wide tables (C >> 10) with many indexes (I >> 20) this degrades noticeably.
+# A table with 50 indexes × 10 columns per index = 500 unnecessary string comparisons
+# per rename_column call — multiplied across every ALTER TABLE in a large migration.
+#
+# Fix: convert index.columns to a Set before the include? check.
+# Array#index (position lookup) is called at most once per index and remains O(C)
+# but that is not inside an inner loop, so it is acceptable.
+#
+# Complexity before: O(I × C)
+# Complexity after:  O(I + C)  — Set construction O(C) + O(1) lookup per index