Add system check for missing database indexes (#30888)

app/lib/admin/db/schema_parser.rb

@@ -0,0 +1,92 @@
+# frozen_string_literal: true
+
+class Admin::Db::SchemaParser
+  class Index
+    attr_reader :name, :table_name, :columns, :options
+
+    def initialize(name:, table_name:, columns:, options:)
+      @name = name
+      @table_name = table_name
+      @columns = columns
+      @options = options
+    end
+  end
+
+  attr_reader :indexes_by_table
+
+  def initialize(source)
+    parse(source)
+  end
+
+  private
+
+  def parse(source)
+    @indexes_by_table = {}
+    queue = [Prism.parse(source).value]
+    while (node = queue.shift)
+      if node.type == :call_node && node.name == :create_table
+        parse_create_table(node)
+      elsif node.type == :call_node && node.name == :add_index
+        parse_add_index(node)
+      else
+        queue.concat(node.compact_child_nodes)
+      end
+    end
+  end
+
+  def parse_create_table(node)
+    table_name = parse_arguments(node).first
+    queue = node.compact_child_nodes
+    while (node = queue.shift)
+      if node.type == :call_node && node.name == :index
+        parse_index(node, table_name:)
+      else
+        queue.concat(node.compact_child_nodes)
+      end
+    end
+  end
+
+  def parse_index(node, table_name:)
+    arguments = parse_arguments(node)
+    save_index(
+      name: arguments.last[:name],
+      table_name: table_name,
+      columns: arguments.first,
+      options: arguments.last
+    )
+  end
+
+  def parse_add_index(node)
+    arguments = parse_arguments(node)
+    save_index(
+      name: arguments.last[:name],
+      table_name: arguments.first,
+      columns: arguments[1],
+      options: arguments.last
+    )
+  end
+
+  def parse_arguments(node)
+    node.arguments.arguments.map { |a| parse_argument(a) }
+  end
+
+  def parse_argument(argument)
+    case argument
+    when Prism::StringNode
+      argument.unescaped
+    when Prism::SymbolNode
+      argument.unescaped.to_sym
+    when Prism::ArrayNode
+      argument.elements.map { |e| parse_argument(e) }
+    when Prism::KeywordHashNode
+      argument.elements.to_h do |element|
+        [element.key.unescaped.to_sym, parse_argument(element.value)]
+      end
+    end
+  end
+
+  def save_index(name:, table_name:, columns:, options:)
+    @indexes_by_table[table_name] ||= []
+    @indexes_by_table[table_name] << Index.new(name:, table_name:, columns:, options:)
+  end
+end

app/lib/admin/system_check.rb

@@ -8,6 +8,7 @@ class Admin::SystemCheck
     Admin::SystemCheck::SidekiqProcessCheck,
     Admin::SystemCheck::RulesCheck,
     Admin::SystemCheck::ElasticsearchCheck,
+    Admin::SystemCheck::MissingIndexesCheck,
   ].freeze
 
   def self.perform(current_user)

app/lib/admin/system_check/missing_indexes_check.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+class Admin::SystemCheck::MissingIndexesCheck < Admin::SystemCheck::BaseCheck
+  def skip?
+    !current_user.can?(:view_devops)
+  end
+
+  def pass?
+    missing_indexes.none?
+  end
+
+  def message
+    Admin::SystemCheck::Message.new(:missing_indexes_check, missing_indexes.join(', '))
+  end
+
+  private
+
+  def missing_indexes
+    @missing_indexes ||= begin
+      expected_indexes_by_table.flat_map do |table, indexes|
+        expected_indexes = indexes.map(&:name)
+        expected_indexes - existing_indexes_for(table)
+      end
+    end
+  end
+
+  def expected_indexes_by_table
+    schema_rb = Rails.root.join('db', 'schema.rb').read
+    schema_parser = Admin::Db::SchemaParser.new(schema_rb)
+    schema_parser.indexes_by_table
+  end
+
+  def existing_indexes_for(table)
+    ActiveRecord::Base.connection.indexes(table).map(&:name)
+  end
+end