運維筆記--postgresql占用CPU問題定位

場景描述：

?業務系統訪問變慢，登陸服務器查看系統負載并不高，然后查看占用CPU較高的進程，發現是連接數據庫的幾個進程占用系統資源較多。

處理方式：

查找出占用系統內存&CPU排名前10的進程：[或者用top命令查看] ?---這里需要注意，如果用了容器，需要進入容器內部查看相應的進程。

ps aux|head -1;ps aux|grep -v PID|sort -rn -k +3|head

切換到postgres用戶，執行psql，進入數據庫終端：指定上述命令找到的系統進程號

SELECT procpid, START, now() - START AS lap, current_query FROM ( SELECT backendid, pg_stat_get_backend_pid (S.backendid) AS procpid,pg_stat_get_backend_activity_start (S.backendid) AS START,pg_stat_get_backend_activity (S.backendid) AS current_query FROM (SELECT pg_stat_get_backend_idset () AS backendid) AS S) AS S WHERE current_query <> '<IDLE>' and procpid=15874 ORDER BY lap DESC;

定位到SQL，確認該SQL完成的業務查詢功能，查看執行計劃，增加索引or 修改代碼。

SELECT "******_edoc_queue".id FROM "******_edoc_queue" WHERE (("*******_edoc_queue"."edoc_id" = '521300000004TCS60515001FV-960157.pdf') AND ("*****_edoc_queue"."active" = true)) ORDER BY "*****_edoc_queue"."id"

?查詢該條SQL的執行計劃：（Postgresql使用explain analyze + sql語法的格式）

postgres=# \c ***你的實際模式schema You are now connected to database "stbg" as user "postgres". stbg=# explain analyze SELECT "cus_center_new_edoc_queue".id FROM "cus_center_new_edoc_queue" WHERE (("cus_center_new_edoc_queue"."edoc_id" = '521300000008TCS60417066FV-960101.pdf') AND ("cus_center_new_edoc_queue"."active" = true)) ORDER BY "cus_center_new_edoc_queue"."id";---得到如下執行計劃： stbg= BY "cus_center_new_edoc_queue"."id";ter_new_edoc_queue"."active" = true)) ORDER QUERY PLAN ----------------------------------------------------------------------------- Sort (cost=21044.85..21044.85 rows=1 width=4) (actual time=109.905..109.905 ro ws=0 loops=1)Sort Key: idSort Method: quicksort Memory: 25kB-> Seq Scan on cus_center_new_edoc_queue (cost=0.00..21044.84 rows=1 width=4) (actual time=109.880..109.880 rows=0 loops=1)Filter: (active AND ((edoc_id)::text = '521300000008TCS60417066FV-960101.pdf'::text))Rows Removed by Filter: 583348Planning time: 0.468 msExecution time: 109.952 ms (8 rows)----可以看出執行查詢時間：109.952 ms

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轉載于:https://www.cnblogs.com/hellojesson/p/10911034.html

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