企业营销方案案例范文,网站seo搜索引擎优化教程,网站开发及维护费用,二手房网站建设PgSQL技术内幕-Analyze做的那些事-pg_stat_all_tables pg_stat_all_tables视图中记录有analyze信息#xff0c;比如何时做的analyze、表元组个数#xff08;活元组、死元组#xff09;等。重启后发现该视图中表的统计信息重置不见了#xff0c;发生了什么#xff1f; 1、p… PgSQL技术内幕-Analyze做的那些事-pg_stat_all_tables pg_stat_all_tables视图中记录有analyze信息比如何时做的analyze、表元组个数活元组、死元组等。重启后发现该视图中表的统计信息重置不见了发生了什么 1、pg_stat_all_tables 先理解下该视图该视图定义如下。从视图定义可以看到相关统计信息都是通过一系列函数获取的 yzs# \d pg_stat_all_tables视图 pg_catalog.pg_stat_all_tables栏位 | 类型 | 校对规则 | 可空的 | 预设 | 存储 | 描述
------------------------------------------------------------------------------------relid | oid | | | | plain |schemaname | name | | | | plain |relname | name | | | | plain |seq_scan | bigint | | | | plain |seq_tup_read | bigint | | | | plain |idx_scan | bigint | | | | plain |idx_tup_fetch | bigint | | | | plain |n_tup_ins | bigint | | | | plain |n_tup_upd | bigint | | | | plain |n_tup_del | bigint | | | | plain |n_tup_hot_upd | bigint | | | | plain |n_live_tup | bigint | | | | plain |n_dead_tup | bigint | | | | plain |n_mod_since_analyze | bigint | | | | plain |last_vacuum | timestamp with time zone | | | | plain |last_autovacuum | timestamp with time zone | | | | plain |last_analyze | timestamp with time zone | | | | plain |last_autoanalyze | timestamp with time zone | | | | plain |vacuum_count | bigint | | | | plain |autovacuum_count | bigint | | | | plain |analyze_count | bigint | | | | plain |autoanalyze_count | bigint | | | | plain |
视图定义:SELECT c.oid AS relid,n.nspname AS schemaname,c.relname,pg_stat_get_numscans(c.oid) AS seq_scan,pg_stat_get_tuples_returned(c.oid) AS seq_tup_read,sum(pg_stat_get_numscans(i.indexrelid))::bigint AS idx_scan,sum(pg_stat_get_tuples_fetched(i.indexrelid))::bigint pg_stat_get_tuples_fetched(c.oid) AS idx_tup_fetch,pg_stat_get_tuples_inserted(c.oid) AS n_tup_ins,pg_stat_get_tuples_updated(c.oid) AS n_tup_upd,pg_stat_get_tuples_deleted(c.oid) AS n_tup_del,pg_stat_get_tuples_hot_updated(c.oid) AS n_tup_hot_upd,pg_stat_get_live_tuples(c.oid) AS n_live_tup,pg_stat_get_dead_tuples(c.oid) AS n_dead_tup,pg_stat_get_mod_since_analyze(c.oid) AS n_mod_since_analyze,pg_stat_get_last_vacuum_time(c.oid) AS last_vacuum,pg_stat_get_last_autovacuum_time(c.oid) AS last_autovacuum,pg_stat_get_last_analyze_time(c.oid) AS last_analyze,pg_stat_get_last_autoanalyze_time(c.oid) AS last_autoanalyze,pg_stat_get_vacuum_count(c.oid) AS vacuum_count,pg_stat_get_autovacuum_count(c.oid) AS autovacuum_count,pg_stat_get_analyze_count(c.oid) AS analyze_count,pg_stat_get_autoanalyze_count(c.oid) AS autoanalyze_countFROM pg_class cLEFT JOIN pg_index i ON c.oid i.indrelidLEFT JOIN pg_namespace n ON n.oid c.relnamespaceWHERE c.relkind ANY (ARRAY[r::char, t::char, m::char])GROUP BY c.oid, n.nspname, c.relname; 我们以n_live_tup这一列为例看下这个统计信息来自哪里。需要梳理下pg_stat_get_live_tuples函数可以看到统计信息来自pg_stat_tmp/global.stat由配置项pgstat_temp_directory控制默认pg_stat_tmp 2、正常关闭服务 关闭服务前统计信息文件位于pg_stat_tmp 关闭服务后统计信息文件移动到了pg_stat 3、再次正常启动服务 发现统计信息文件又移动到了pg_stat_tmp。此时查看pg_stat_all_tables视图发现统计信息是存在的 为什么重启后统计信息并没有重置呢 经分析在崩溃重启恢复时会将pg_stat_tmp和pg_stat目录都进行重置此后重启成功后因没有统计信息文件就导致pg_stat_all_tables视图中的信息为空了
