運(yùn)維筆記--postgresql占用CPU問題定位

場(chǎng)景描述：

?業(yè)務(wù)系統(tǒng)訪問變慢，登陸服務(wù)器查看系統(tǒng)負(fù)載并不高，然后查看占用CPU較高的進(jìn)程，發(fā)現(xiàn)是連接數(shù)據(jù)庫的幾個(gè)進(jìn)程占用系統(tǒng)資源較多。

處理方式：

查找出占用系統(tǒng)內(nèi)存&CPU排名前10的進(jìn)程：[或者用top命令查看] ?---這里需要注意，如果用了容器，需要進(jìn)入容器內(nèi)部查看相應(yīng)的進(jìn)程。

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

切換到postgres用戶，執(zhí)行psql，進(jìn)入數(shù)據(jù)庫終端：指定上述命令找到的系統(tǒng)進(jìn)程號(hào)

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(rèn)該SQL完成的業(yè)務(wù)查詢功能，查看執(zhí)行計(jì)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?cè)摋lSQL的執(zhí)行計(jì)劃：（Postgresql使用explain analyze + sql語法的格式）

postgres=# \c ***你的實(shí)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(zhí)行計(jì)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(zhí)行查詢時(shí)間：109.952 ms

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轉(zhuǎn)載于:https://www.cnblogs.com/hellojesson/p/10911034.html

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