我们希望通过Prometheus中的postgres_exporter获得PostgreSQL的CPU使用率。
每个doc有三个与CPU相关的指标：

# HELP pg_settings_cpu_index_tuple_cost Sets the planner's estimate of the cost of processing each index entry during an index scan.
# TYPE pg_settings_cpu_index_tuple_cost gauge
pg_settings_cpu_index_tuple_cost{server="localhost:5432"} 0.005
# HELP pg_settings_cpu_operator_cost Sets the planner's estimate of the cost of processing each operator or function call.
# TYPE pg_settings_cpu_operator_cost gauge
pg_settings_cpu_operator_cost{server="localhost:5432"} 0.0025
# HELP pg_settings_cpu_tuple_cost Sets the planner's estimate of the cost of processing each tuple (row).
# TYPE pg_settings_cpu_tuple_cost gauge
pg_settings_cpu_tuple_cost{server="localhost:5432"} 0.01

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我们认为CPU使用率可以通过以下方式计算：

avg by (server) (avg_over_time(pg_settings_cpu_index_tuple_cost[2m]) + avg_over_time(pg_settings_cpu_tuple_cost[2m]) + avg_over_time(pg_settings_cpu_operator_cost[2m]) ) * 100

型
我们不知道上面的计算是否正确。有人能帮我们再检查一遍吗？或者我们遗漏了什么？