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