module PgsqlStats
  class Index
    include ActionView::Helpers::NumberHelper
    
    attr_accessor :oid, :table_oid, :name, :table_name, :schema_name, :scans, :entries_read, :rows_fetched,
      :blocks_read, :cache_hits
    
    attr_accessor :analysis

    def initialize(connection, row, io_row)
      @connection = connection
      @analysis = nil
      load(row)
      load_io(io_row)
    end
    
    def refresh
      @connection.transaction do
        load(@connection.select_one("SELECT * FROM pg_stat_all_indexes WHERE indexrelid = #{oid}"))
        load_io(@connection.select_one("SELECT * FROM pg_statio_all_indexes WHERE indexrelid = #{oid}"))
      end
      @analysis = nil
      @pages = nil
      @table = nil
    end
    
    def table
      unless @table
        stats = @connection.select_one("SELECT * FROM pg_stat_all_tables WHERE relid = #{table_oid}")
        io = @connection.select_one("SELECT * FROM pg_statio_all_tables WHERE relid = #{table_oid}")
        @table = Table.new(@connection, stats, io)
      end
      @table
    end
    
    def cache_hit_rate
      cache_hits.to_f / (blocks_read + cache_hits) * 100
    end
    
    def pages
      @pages ||= @connection.select_one("SELECT SUM(relpages) FROM pg_class WHERE relname = '#{name}'")["sum"].to_i
    end
    
    private
    
    def load(row)
      self.oid = row["indexrelid"].to_i
      self.table_oid = row["relid"].to_i
      self.name = row["indexrelname"]
      self.table_name = row["relname"]
      self.schema_name = row["schemaname"]
      self.scans = row["idx_scan"].to_i
      self.entries_read = row["idx_tup_read"].to_i
      self.rows_fetched = row["idx_tup_fetch"].to_i
    end
    
    def load_io(row)
      self.blocks_read = row["idx_blks_read"].to_i
      self.cache_hits = row["idx_blks_hit"].to_i
    end
  end
end