PostgreSQL實時健康監控大屏-低頻指標

德哥發表於2018-09-15
SQL指標

標籤

PostgreSQL , 大屏指標 , qps , long query , locks , active , idle in transaction , long idle in transaction , 2PC

背景

最關鍵的一些資料庫健康指標，趨勢監測。

1 資料年齡

年齡不能超過20億（大概值），建議當達到15億時，應儘快安排freeze。

postgres=# select datname,age(datfrozenxid) from pg_database order by 2 desc;  
  datname  |    age      
-----------+-----------  
 postgres  | 172127964  
 template1 | 172127964  
 template0 | 172127964  
 test      | 172127964  
(4 rows)

2 年齡大於N的物件佔用空間數

年齡大於12億的資料庫，佔用的空間數

postgres=# select pg_size_pretty(sum(pg_database_size(oid))) from pg_database where age(datfrozenxid)>1200000000;  
 pg_size_pretty   
----------------  
   
(1 row)

3 freeze 風暴預測

《PostgreSQL Freeze 風暴預測續 – 珍藏級SQL》

4 表膨脹

https://raw.githubusercontent.com/digoal/pgsql_admin_script/master/generate_report.sh

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `SELECT  
  current_database() AS db, schemaname, tablename, reltuples::bigint AS tups, relpages::bigint AS pages, otta,  
  ROUND(CASE WHEN otta=0 OR sml.relpages=0 OR sml.relpages=otta THEN 0.0 ELSE sml.relpages/otta::numeric END,1) AS tbloat,  
  CASE WHEN relpages < otta THEN 0 ELSE relpages::bigint - otta END AS wastedpages,  
  CASE WHEN relpages < otta THEN 0 ELSE bs*(sml.relpages-otta)::bigint END AS wastedbytes,  
  CASE WHEN relpages < otta THEN $$0 bytes$$::text ELSE (bs*(relpages-otta))::bigint || $$ bytes$$ END AS wastedsize,  
  iname, ituples::bigint AS itups, ipages::bigint AS ipages, iotta,  
  ROUND(CASE WHEN iotta=0 OR ipages=0 OR ipages=iotta THEN 0.0 ELSE ipages/iotta::numeric END,1) AS ibloat,  
  CASE WHEN ipages < iotta THEN 0 ELSE ipages::bigint - iotta END AS wastedipages,  
  CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta) END AS wastedibytes,  
  CASE WHEN ipages < iotta THEN $$0 bytes$$ ELSE (bs*(ipages-iotta))::bigint || $$ bytes$$ END AS wastedisize,  
  CASE WHEN relpages < otta THEN  
    CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta::bigint) END  
    ELSE CASE WHEN ipages < iotta THEN bs*(relpages-otta::bigint)  
      ELSE bs*(relpages-otta::bigint + ipages-iotta::bigint) END  
  END AS totalwastedbytes  
FROM (  
  SELECT  
    nn.nspname AS schemaname,  
    cc.relname AS tablename,  
    COALESCE(cc.reltuples,0) AS reltuples,  
    COALESCE(cc.relpages,0) AS relpages,  
    COALESCE(bs,0) AS bs,  
    COALESCE(CEIL((cc.reltuples*((datahdr+ma-  
      (CASE WHEN datahdr%ma=0 THEN ma ELSE datahdr%ma END))+nullhdr2+4))/(bs-20::float)),0) AS otta,  
    COALESCE(c2.relname,$$?$$) AS iname, COALESCE(c2.reltuples,0) AS ituples, COALESCE(c2.relpages,0) AS ipages,  
    COALESCE(CEIL((c2.reltuples*(datahdr-12))/(bs-20::float)),0) AS iotta -- very rough approximation, assumes all cols  
  FROM  
     pg_class cc  
  JOIN pg_namespace nn ON cc.relnamespace = nn.oid AND nn.nspname <> $$information_schema$$  
  LEFT JOIN  
  (  
    SELECT  
      ma,bs,foo.nspname,foo.relname,  
      (datawidth+(hdr+ma-(case when hdr%ma=0 THEN ma ELSE hdr%ma END)))::numeric AS datahdr,  
      (maxfracsum*(nullhdr+ma-(case when nullhdr%ma=0 THEN ma ELSE nullhdr%ma END))) AS nullhdr2  
    FROM (  
      SELECT  
        ns.nspname, tbl.relname, hdr, ma, bs,  
        SUM((1-coalesce(null_frac,0))*coalesce(avg_width, 2048)) AS datawidth,  
        MAX(coalesce(null_frac,0)) AS maxfracsum,  
        hdr+(  
          SELECT 1+count(*)/8  
          FROM pg_stats s2  
          WHERE null_frac<>0 AND s2.schemaname = ns.nspname AND s2.tablename = tbl.relname  
        ) AS nullhdr  
      FROM pg_attribute att   
      JOIN pg_class tbl ON att.attrelid = tbl.oid  
      JOIN pg_namespace ns ON ns.oid = tbl.relnamespace   
      LEFT JOIN pg_stats s ON s.schemaname=ns.nspname  
      AND s.tablename = tbl.relname  
      AND s.inherited=false  
      AND s.attname=att.attname,  
      (  
        SELECT  
          (SELECT current_setting($$block_size$$)::numeric) AS bs,  
            CASE WHEN SUBSTRING(SPLIT_PART(v, $$ $$, 2) FROM $$#"[0-9]+.[0-9]+#"%$$ for $$#$$)  
              IN ($$8.0$$,$$8.1$$,$$8.2$$) THEN 27 ELSE 23 END AS hdr,  
          CASE WHEN v ~ $$mingw32$$ OR v ~ $$64-bit$$ THEN 8 ELSE 4 END AS ma  
        FROM (SELECT version() AS v) AS foo  
      ) AS constants  
      WHERE att.attnum > 0 AND tbl.relkind=$$r$$  
      GROUP BY 1,2,3,4,5  
    ) AS foo  
  ) AS rs  
  ON cc.relname = rs.relname AND nn.nspname = rs.nspname  
  LEFT JOIN pg_index i ON indrelid = cc.oid  
  LEFT JOIN pg_class c2 ON c2.oid = i.indexrelid  
) AS sml order by wastedbytes desc limit 5`  
done

5 索引膨脹

https://raw.githubusercontent.com/digoal/pgsql_admin_script/master/generate_report.sh

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `SELECT  
  current_database() AS db, schemaname, tablename, reltuples::bigint AS tups, relpages::bigint AS pages, otta,  
  ROUND(CASE WHEN otta=0 OR sml.relpages=0 OR sml.relpages=otta THEN 0.0 ELSE sml.relpages/otta::numeric END,1) AS tbloat,  
  CASE WHEN relpages < otta THEN 0 ELSE relpages::bigint - otta END AS wastedpages,  
  CASE WHEN relpages < otta THEN 0 ELSE bs*(sml.relpages-otta)::bigint END AS wastedbytes,  
  CASE WHEN relpages < otta THEN $$0 bytes$$::text ELSE (bs*(relpages-otta))::bigint || $$ bytes$$ END AS wastedsize,  
  iname, ituples::bigint AS itups, ipages::bigint AS ipages, iotta,  
  ROUND(CASE WHEN iotta=0 OR ipages=0 OR ipages=iotta THEN 0.0 ELSE ipages/iotta::numeric END,1) AS ibloat,  
  CASE WHEN ipages < iotta THEN 0 ELSE ipages::bigint - iotta END AS wastedipages,  
  CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta) END AS wastedibytes,  
  CASE WHEN ipages < iotta THEN $$0 bytes$$ ELSE (bs*(ipages-iotta))::bigint || $$ bytes$$ END AS wastedisize,  
  CASE WHEN relpages < otta THEN  
    CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta::bigint) END  
    ELSE CASE WHEN ipages < iotta THEN bs*(relpages-otta::bigint)  
      ELSE bs*(relpages-otta::bigint + ipages-iotta::bigint) END  
  END AS totalwastedbytes  
FROM (  
  SELECT  
    nn.nspname AS schemaname,  
    cc.relname AS tablename,  
    COALESCE(cc.reltuples,0) AS reltuples,  
    COALESCE(cc.relpages,0) AS relpages,  
    COALESCE(bs,0) AS bs,  
    COALESCE(CEIL((cc.reltuples*((datahdr+ma-  
      (CASE WHEN datahdr%ma=0 THEN ma ELSE datahdr%ma END))+nullhdr2+4))/(bs-20::float)),0) AS otta,  
    COALESCE(c2.relname,$$?$$) AS iname, COALESCE(c2.reltuples,0) AS ituples, COALESCE(c2.relpages,0) AS ipages,  
    COALESCE(CEIL((c2.reltuples*(datahdr-12))/(bs-20::float)),0) AS iotta -- very rough approximation, assumes all cols  
  FROM  
     pg_class cc  
  JOIN pg_namespace nn ON cc.relnamespace = nn.oid AND nn.nspname <> $$information_schema$$  
  LEFT JOIN  
  (  
    SELECT  
      ma,bs,foo.nspname,foo.relname,  
      (datawidth+(hdr+ma-(case when hdr%ma=0 THEN ma ELSE hdr%ma END)))::numeric AS datahdr,  
      (maxfracsum*(nullhdr+ma-(case when nullhdr%ma=0 THEN ma ELSE nullhdr%ma END))) AS nullhdr2  
    FROM (  
      SELECT  
        ns.nspname, tbl.relname, hdr, ma, bs,  
        SUM((1-coalesce(null_frac,0))*coalesce(avg_width, 2048)) AS datawidth,  
        MAX(coalesce(null_frac,0)) AS maxfracsum,  
        hdr+(  
          SELECT 1+count(*)/8  
          FROM pg_stats s2  
          WHERE null_frac<>0 AND s2.schemaname = ns.nspname AND s2.tablename = tbl.relname  
        ) AS nullhdr  
      FROM pg_attribute att   
      JOIN pg_class tbl ON att.attrelid = tbl.oid  
      JOIN pg_namespace ns ON ns.oid = tbl.relnamespace   
      LEFT JOIN pg_stats s ON s.schemaname=ns.nspname  
      AND s.tablename = tbl.relname  
      AND s.inherited=false  
      AND s.attname=att.attname,  
      (  
        SELECT  
          (SELECT current_setting($$block_size$$)::numeric) AS bs,  
            CASE WHEN SUBSTRING(SPLIT_PART(v, $$ $$, 2) FROM $$#"[0-9]+.[0-9]+#"%$$ for $$#$$)  
              IN ($$8.0$$,$$8.1$$,$$8.2$$) THEN 27 ELSE 23 END AS hdr,  
          CASE WHEN v ~ $$mingw32$$ OR v ~ $$64-bit$$ THEN 8 ELSE 4 END AS ma  
        FROM (SELECT version() AS v) AS foo  
      ) AS constants  
      WHERE att.attnum > 0 AND tbl.relkind=$$r$$  
      GROUP BY 1,2,3,4,5  
    ) AS foo  
  ) AS rs  
  ON cc.relname = rs.relname AND nn.nspname = rs.nspname  
  LEFT JOIN pg_index i ON indrelid = cc.oid  
  LEFT JOIN pg_class c2 ON c2.oid = i.indexrelid  
) AS sml order by wastedibytes desc limit 5`  
done

6 TOP SQL

《PostgreSQL 如何查詢TOP SQL (例如IO消耗最高的SQL) – 珍藏級》

7 未使用索引

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_indexes where idx_scan=0 or idx_tup_read=0 or idx_tup_fetch=0;  
`  
done

8 未使用(查詢)表

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_tables where seq_scan=0 and idx_scan=0;  
`  
done

9 熱表

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_tables order by seq_scan+idx_scan desc limit 10;  
`  
done

10 冷表

針對性刪除表，或者使用OSS冷儲存。

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_tables order by seq_scan+idx_scan limit 10;  
`  
done

11 熱索引

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_indexes order by idx_scan desc limit 10;  
`  
done

12 冷索引

針對性刪除索引。

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_indexes order by idx_scan limit 10;  
`  
done

13 全表掃描次數TOP物件

針對性建立索引。

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_tables order by seq_scan desc limit 10;  
`  
done

14 全表掃描返回記錄數TOP物件

針對性建立索引。

for db in `psql --pset=pager=off -t -A -q -c `select datname from pg_database where datname not in ($$template0$$, $$template1$$)``  
do  
psql -d $db --pset=pager=off -q -x -c `  
select current_database(),* from pg_stat_all_tables order by seq_tup_read desc limit 10;  
`  
done

15 監控統計資訊不準的物件（表、物化檢視）

背景知識

1、建立測試表

postgres=# create table a(id int);  
CREATE TABLE

2、禁止收集統計資訊

postgres=# alter table a set (autovacuum_enabled =off);  
ALTER TABLE

3、寫入大量資料

postgres=# insert into a select generate_series(1,10000000);  
INSERT 0 10000000

4、檢視統計資訊項，目前佔用多少空間（pages）

postgres=# select relpages from pg_class where relname=`a`;  
 relpages   
----------  
        0  
(1 row)

5、檢視真實空間佔用

postgres=# select pg_relation_size(`a`);  
 pg_relation_size   
------------------  
        362479616  
(1 row)

6、真實空間佔用，轉換為PAGES

postgres=# select pg_relation_size(`a`)/current_setting(`block_size`)::float8;  
 ?column?   
----------  
    44248  
(1 row)

7、收集統計資訊，檢視統計資訊項，目前佔用多少空間（pages）

postgres=# analyze a;  
ANALYZE  
  
postgres=# select relpages from pg_class where relname=`a`;  
 relpages   
----------  
    44248  
(1 row)

8、根據以上原理，可以設計評估統計資訊不準確的表 SQL如下：

select oid::regclass as table, relpages, pg_relation_size(oid)/current_setting(`block_size`)::float8 as real_pages from pg_class   
where relkind in (`r`, `m`)  -- 表和物化檢視  
and pg_relation_size(oid) > 1048576  -- 大於1MB  
and (pg_relation_size(oid)/current_setting(`block_size`)::float8 - relpages)/(pg_relation_size(oid)/current_setting(`block_size`)::float8) > 0.2;  -- 大於 20% 偏差   
  
  
 table | relpages | real_pages   
-------+----------+------------  
 a     |        0 |      44248  
(1 row)

核心增加功能

1、讀寫磁碟吞吐快照區間統計，區分索引，表，垃圾回收，FREEZE，AUTOANALYZE。分類統計。

2、鎖等待時長快照區間統計，區分鎖粒度，下鑽到物件。

注意

stat的資訊在使用pg_stat_reset()後會清零。請注意。

參考

https://raw.githubusercontent.com/digoal/pgsql_admin_script/master/generate_report.sh

《PostgreSQL Freeze 風暴預測續 – 珍藏級SQL》


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