xiaolei everdance

rgreenjr / postgres_queries_and_commands.sql

Last active September 19, 2024 05:47

Useful PostgreSQL Queries and Commands

	-- show running queries (pre 9.2)
	SELECT procpid, age(clock_timestamp(), query_start), usename, current_query
	FROM pg_stat_activity
	WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%'
	ORDER BY query_start desc;

	-- show running queries (9.2)
	SELECT pid, age(clock_timestamp(), query_start), usename, query
	FROM pg_stat_activity
	WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'

jboner / latency.txt

Last active September 20, 2024 12:40

Latency Numbers Every Programmer Should Know

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD

cjus / jsonval.sh

Created June 26, 2011 17:42

Extract a JSON value from a BASH script

	#!/bin/bash
	function jsonval {
	temp=`echo $json \| sed 's/\\\\\//\//g' \| sed 's/[{}]//g' \| awk -v k="text" '{n=split($0,a,","); for (i=1; i<=n; i++) print a[i]}' \| sed 's/\"\:\"/\\|/g' \| sed 's/[\,]/ /g' \| sed 's/\"//g' \| grep -w $prop`
	echo ${temp##*\|}
	}

	json=`curl -s -X GET http://twitter.com/users/show/$1.json`
	prop='profile_image_url'
	picurl=`jsonval`