Federico Mengozzi fedemengo

PSQL

Magic words:

psql -U postgres

Some interesting flags (to see all, use -h or --help depending on your psql version):

-E: will describe the underlaying queries of the \ commands (cool for learning!)
-l: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)

foobar, foo, bar, baz, qux, quux, corge, grault, garply, waldo, fred, plugh, xyzzy, thud

ASCII.jp：技術文書に頻出する「foobar」って何だ？｜今さら聞けないIT英語

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

	/**
	* In this code we have a very large array called arr, and very large set of operations
	* Operation #1: Increment the elements within range [i, j] with value val
	* Operation #2: Get max element within range [i, j]
	* Build tree: build_tree(1, 0, N-1)
	* Update tree: update_tree(1, 0, N-1, i, j, value)
	* Query tree: query_tree(1, 0, N-1, i, j)
	* Actual space required by the tree = 2*2^ceil(log_2(n)) - 1
	*/

	# /home/terrywang/.tmux.conf
	# Based on tmux book written by Brian P. Hogan
	# c-a o to switch to another panel
	# c-d to close shell
	# c-a ! to close panel
	# c-a w to list windows
	# c-a " split pane horizontally
	# c-a % split pane vertically

	# Setting the prefix from C-b to C-a

	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

	#! /usr/bin/env python

	""" Convert values between RGB hex codes and xterm-256 color codes.

	Nice long listing of all 256 colors and their codes. Useful for
	developing console color themes, or even script output schemes.

	Resources:
	* http://en.wikipedia.org/wiki/8-bit_color
	* http://en.wikipedia.org/wiki/ANSI_escape_code

	# Run this in the project repo from the command-line
	# http://stackoverflow.com/a/4593065/99923

	git log --shortstat --author "Xeoncross" --since "2 weeks ago" --until "1 week ago" \| grep "files changed" \| awk '{files+=$1; inserted+=$4; deleted+=$6} END {print "files changed", files, "lines inserted:", inserted, "lines deleted:", deleted}'