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‎202101/20210130_02.md‎

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@@ -46,7 +46,7 @@ ssh登录ip，自动输入密码, vim ~/sshlogin
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```
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#!/usr/bin/expect #使用expect解释器
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spawn ssh [email protected] #开启一个进程ssh
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spawn ssh -o TCPKeepAlive=yes -o ServerAliveInterval=15 -o ServerAliveCountMax=3 [email protected] #开启一个进程ssh
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expect {
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"yes/no" { send "yes\r"; exp_continue } #当匹配到"yes/no时，就是需要你输入yes or no时，发送yes字符串，\r带表回车；exp_continue继续匹配
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"password:" { send "sanshen6677\r" } #当匹配到password，就是该输入密码，发送密码，并\r回车。注意{之前要有空格。

‎202101/20210130_04.md‎

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@@ -88,20 +88,20 @@ OutSystems在低代码界激起的水花被同期接力到了国内的资本市
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- 随随便便就上百个表的JOIN性能
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## 解法
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1、无法律风险
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## PG解法
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### 1、无法律风险
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不论是你来分发, 还是用户自己安装, 都没有法律风险.
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2、免费
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### 2、免费
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不要钱很重要
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3、多租户
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### 3、多租户
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schema/database 级别多租户
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4、多模
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### 4、多模
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json|xml|hstore|cube schemaless支持
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图式查询支持
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流订阅
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10余种索引(btree,hash,gin,gist,spgist,brin,bloom,rum,pase(阿里云),zombodb)
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5、大量国产数据库都基于PG
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### 5、大量国产数据库都基于PG
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华为opengauss
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阿里polardb pg-o
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腾讯tbase, cynosdb
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亚信antdb
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中兴goldendb
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阿里云adb pg
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6、可扩展插件, 打出垂直行业技术壁垒
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### 6、可扩展插件, 打出垂直行业技术壁垒
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不需要修改内核, 通过API能支持数据库的功能扩展, 在数据库中支持行业特性, 例如:
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rdkit, 医疗、化学行业, 化学分子式计算
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同时开源提供了很多插件可直接使用.
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https://pgxn.org/
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7、横向扩展
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### 7、横向扩展
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Citus, 可以横向扩展到PB级别
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8、平滑加减字段, 修改字段长度
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### 8、平滑加减字段, 修改字段长度
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低代码下, 数据模型的要求是最灵活的, 匹配用户定制化的功能模块, 加减字段, 修改字段一定很频繁.
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PG支持平滑加减,修改字段长度(大量不需要rewrite)
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9、在线加索引
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### 9、在线加索引
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低代码下, 数据模型的要求是最灵活的, 匹配用户定制化的功能模块, 平滑加索引很重要.
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如果加个索引要锁表, 是不是要疯掉,根本无法满足敏捷要求.
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10、自动推荐索引
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### 10、自动推荐索引
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低代码下, 数据模型的要求是最灵活的, 匹配用户定制化的功能模块, ORM提供的SQL变化无穷, 支持自动推荐索引, 大量简化SaaS厂商优化工作量.
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10、在线垃圾回收
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### 11、在线垃圾回收
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不堵塞用户操作.
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11、优化器, 高级优化器
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### 12、优化器, 高级优化器
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低代码下, 数据模型的要求是最灵活的, 匹配用户定制化的功能模块, ORM提供的SQL变化无穷, 复杂SQL能不能优化好, 是很重要的能力.
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支持数百种数据访问方法, 支持CBO和遗传算法(超多表JOIN优化), 支持扩展aqo(基于机器学习的超多表JOIN动态优化)
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12、并行计算
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### 13、并行计算
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跑个报表是多么低的要求啊, 但是怎么才能快, 天下武功唯快不破.
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PG支持几乎任何SQL, 任何NODE都能用多CPU并行.
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10亿数据量,聚合只需要2秒.
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[《PostgreSQL 并行计算解说 汇总》](../201903/20190318_05.md)
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13、稳如泰山
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### 14、稳如泰山
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PG 的稳定性是产业界出了名的, 稳如狗.
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14、功能和Oracle一个级别, 在垂直领域甚至超过Oracle
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### 15、功能和Oracle一个级别, 在垂直领域甚至超过Oracle
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例如odoo是全球最流行的开源SaaS软件, 指定使用PostgreSQL数据库.
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‎202101/20210130_05.md‎

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## PostgreSQL 命令行 top 工具 - pg_activity
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### 作者
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digoal
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### 日期
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2021-01-30
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### 标签
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PostgreSQL , top , pg_activity
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----
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## 背景
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![pg_activity](https://github.com/dalibo/pg_activity/raw/master/docs/imgs/logo-horizontal.png)
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Command line tool for PostgreSQL server activity monitoring.
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[![Latest PyPI version](https://img.shields.io/pypi/v/pg_activity.svg)](https://pypi.python.org/pypi/pg_activity)
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[![Build Status](https://travis-ci.com/dalibo/pg_activity.svg?branch=master)](https://travis-ci.com/dalibo/pg_activity)
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![pg_activity screenshot](https://raw.github.com/dalibo/pg_activity/master/docs/imgs/screenshot.png)
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Installation
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------------
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`pg_activity` requires Python 3.6 or later. It can be installed using pip
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(available, e.g., as `apt install python3-pip` on Debian-based distributions):
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$ python3 -m pip install pg_activity psycopg2-binary
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or directly from your Linux distribution, if available, e.g.:
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$ sudo apt install pg-activity
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Usage
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-----
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`pg_activity` works locally or remotely. In local execution context, to obtain
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sufficient rights to display system informations, the system user running
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`pg_activity` must be the same user running postgresql server (`postgres` by
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default), or have more rights like `root`. Otherwise, `pg_activity` can fallback
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to a degraded mode without displaying system informations. On the same way,
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PostgreSQL user used to connect to the database must be super-user.
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ex:
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sudo -u postgres pg_activity -U postgres
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Options
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-------
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pg_activity [options]
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Options:
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--version Show program's version number and exit
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-U USERNAME, --username=USERNAME
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Database user name (default: "postgres").
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-p PORT, --port=PORT Database server port (default: "5432").
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-h HOSTNAME, --host=HOSTNAME
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Database server host or socket directory (default:
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"localhost").
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-d DBNAME, --dbname=DBNAME
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Database name to connect to (default: "postgres").
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--blocksize=BLOCKSIZE Filesystem blocksize (default: 4096).
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--rds Enable support for AWS RDS.
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--output=FILEPATH Store running queries as CSV.
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--help Show this help message and exit.
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--no-db-size Skip total size of DB.
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--min-duration Don't display queries with smaller than specified
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duration (in seconds).
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--verbose-mode=VERBOSE_MODE
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Queries display mode. Values: 1-TRUNCATED,
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2-FULL(default), 3-INDENTED
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--duration-mode=DURATION_MODE
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Duration mode. Values: 1-QUERY(default),
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2-TRANSACTION, 3-BACKEND
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Display options, you can exclude some columns by using them :
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--no-database Disable DATABASE.
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--no-user Disable USER.
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--no-client Disable CLIENT.
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--no-cpu Disable CPU%.
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--no-mem Disable MEM%.
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--no-read Disable READ/s.
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--no-write Disable WRITE/s.
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--no-time Disable TIME+.
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--no-wait Disable W.
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--no-app-name Disable App.
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Notes
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-----
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Length of SQL query text that `pg_activity` reports relies on PostgreSQL
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parameter `track_activity_query_size`. Default value is `1024` (expressed in
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bytes). If your SQL query text look truncated, you should increase
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`track_activity_query_size`.
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Interactives commands
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---------------------
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| Key | Action |
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|-----------|------------------------------------------------------------------|
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| `r` | Sort by READ/s, descending |
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| `w` | Sort by WRITE/s, descending |
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| `c` | Sort by CPU%, descending |
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| `m` | Sort by MEM%, descending |
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| `t` | Sort by TIME+, descending |
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| `T` | Change duration mode: query, transaction, backend |
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| `Space` | Pause on/off |
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| `v` | Change queries display mode: full, indented, truncated |
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| `UP/DOWN` | Scroll processes list |
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| `k/j` | Scroll processes list |
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| `q` | Quit |
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| `+` | Increase refresh time. Maximum value : 5s |
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| `-` | Decrease refresh time. Minimum Value : 0.5s |
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| `F1/1` | Running queries list |
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| `F2/2` | Waiting queries list |
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| `F3/3` | Blocking queries list |
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| `h` | Help page |
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| `R` | Refresh |
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| `D` | Refresh Database Size (including when --no-dbzise option applied)|
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Navigation mode
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---------------
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| Key | Action |
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|------------|-----------------------------------------------|
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| `UP`/`k` | Move up the cursor |
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| `DOWN`/`j` | Move down the cursor |
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| `K` | Terminate the current backend/tagged backends |
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| `C` | Cancel the current backend/tagged backends |
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| `Space` | Tag or untag the process |
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| `q` | Quit |
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| `Other` | Back to activity |
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FAQ
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---
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**I can't see my queries only TPS is shown**
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`pg_activity` scans the view `pg_stat_activity` with a user defined refresh
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time comprised between O.5 and 5 seconds. It can be modified in the interface
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with the `+` and `-` keys. Any query executed between two scans won't be
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displayed.
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What is more, `pg_activity` uses different queries to get :
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* settings from `pg_settings`
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* version info using `version()`
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* queries and number of connections from `pg_stat_activity`
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* locks from `pg_locks`
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* tps from `pg_database` using `pg_stat_get_db_xact_commit()` and
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`pg_stat_get_db_xact_rollback()`
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* and more ( eg : `pg_cancel_backend()` and `pg_terminate_backend()` )
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Thoses queries cannot be seen in the query tab because all queries issued from
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the `pg_activity` backend are considered as noise and are not displayed . On
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the other hand, the transactions used to get the info for `pg_activity`'s
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reporting are still accounted for by postgres in `pg_stat_get_db_xact_commit()`
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and `pg_stat_get_db_xact_commit()`. Therefore `pg_activity` will display a non
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zero TPS even with no activity on the database, and/or no activity displayed on
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screen.
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#### [PostgreSQL 许愿链接](https://github.com/digoal/blog/issues/76 "269ac3d1c492e938c0191101c7238216")
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您的愿望将传达给PG kernel hacker、数据库厂商等, 帮助提高数据库产品质量和功能, 说不定下一个PG版本就有您提出的功能点. 针对非常好的提议，奖励限量版PG文化衫、纪念品、贴纸、PG热门书籍等，奖品丰富，快来许愿。[开不开森](https://github.com/digoal/blog/issues/76 "269ac3d1c492e938c0191101c7238216").
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#### [9.9元购买3个月阿里云RDS PostgreSQL实例](https://www.aliyun.com/database/postgresqlactivity "57258f76c37864c6e6d23383d05714ea")
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#### [PostgreSQL 解决方案集合](https://yq.aliyun.com/topic/118 "40cff096e9ed7122c512b35d8561d9c8")
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#### [德哥 / digoal's github - 公益是一辈子的事.](https://github.com/digoal/blog/blob/master/README.md "22709685feb7cab07d30f30387f0a9ae")
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![digoal's wechat](../pic/digoal_weixin.jpg "f7ad92eeba24523fd47a6e1a0e691b59")
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‎202101/20210130_06.md‎

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## Linux Mac ssh 客户端长连接防断连 - tcp心跳 TCPKeepAlive,ServerAliveInterval,ServerAliveCountMax
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### 作者
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digoal
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### 日期
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2021-01-30
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### 标签
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PostgreSQL , ssh
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----
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## 背景
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securecrt 可以设置会话option: send protocol no-op 来防止ssh连接长时间没有数据包时被断开.
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linux macos自带的ssh客户端也有同样的参数:
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ServerAliveInterval
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ServerAliveCountMax
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TCPKeepAlive
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实际上PostgreSQL数据库也有类似设置参数
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```
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# - TCP settings -
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# see "man tcp" for details
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#tcp_keepalives_idle = 0 # TCP_KEEPIDLE, in seconds;
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# 0 selects the system default
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#tcp_keepalives_interval = 0 # TCP_KEEPINTVL, in seconds;
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# 0 selects the system default
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#tcp_keepalives_count = 0 # TCP_KEEPCNT;
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# 0 selects the system default
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#tcp_user_timeout = 0 # TCP_USER_TIMEOUT, in milliseconds;
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# 0 selects the system default
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```
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例子:
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```
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ssh -o TCPKeepAlive=yes -o ServerAliveInterval=15 -o ServerAliveCountMax=3 [email protected]
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```
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man ssh_config
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TCPKeepAlive
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Specifies whether the system should send TCP keepalive messages to the other side. If they are sent, death of the connection or crash of one of the machines will be properly noticed. However, this means that connections will die if the route is down temporarily, and some people find it annoying.
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The default is yes (to send TCP keepalive messages), and the client will notice if the network goes down or the remote host dies. This is important in scripts, and many users want it too.
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To disable TCP keepalive messages, the value should be set to no. See also ServerAliveInterval for protocol-level keepalives.
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ServerAliveCountMax
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Sets the number of server alive messages (see below) which may be sent without ssh(1) receiving any messages back from the server. If this threshold is reached while server alive messages are being sent, ssh will disconnect from the server, terminating the session. It is important to note that the use of server alive messages is very different from TCPKeepAlive (below). The server alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option enabled by TCPKeepAlive is spoofable. The server alive mechanism is valuable when the client or server depend on knowing when a connection has become unresponsive.
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The default value is 3. If, for example, ServerAliveInterval (see below) is set to 15 and ServerAliveCountMax is left at the default, if the server becomes unresponsive, ssh will disconnect after approximately 45 seconds.
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ServerAliveInterval
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Sets a timeout interval in seconds after which if no data has been received from the server, ssh(1) will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server.
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#### [PostgreSQL 许愿链接](https://github.com/digoal/blog/issues/76 "269ac3d1c492e938c0191101c7238216")
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您的愿望将传达给PG kernel hacker、数据库厂商等, 帮助提高数据库产品质量和功能, 说不定下一个PG版本就有您提出的功能点. 针对非常好的提议，奖励限量版PG文化衫、纪念品、贴纸、PG热门书籍等，奖品丰富，快来许愿。[开不开森](https://github.com/digoal/blog/issues/76 "269ac3d1c492e938c0191101c7238216").
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#### [9.9元购买3个月阿里云RDS PostgreSQL实例](https://www.aliyun.com/database/postgresqlactivity "57258f76c37864c6e6d23383d05714ea")
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#### [PostgreSQL 解决方案集合](https://yq.aliyun.com/topic/118 "40cff096e9ed7122c512b35d8561d9c8")
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#### [德哥 / digoal's github - 公益是一辈子的事.](https://github.com/digoal/blog/blob/master/README.md "22709685feb7cab07d30f30387f0a9ae")
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![digoal's wechat](../pic/digoal_weixin.jpg "f7ad92eeba24523fd47a6e1a0e691b59")
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