Nima Nasoody nnasoody

PSQL

Magic words:

psql -U postgres

Some interesting flags (to see all, use -h):

-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)

Postgres Cheatsheet

This is a collection of the most common commands I run while administering Postgres databases. The variables shown between the open and closed tags, "<" and ">", should be replaced with a name you choose. Postgres has multiple shortcut functions, starting with a forward slash, "". Any SQL command that is not a shortcut, must end with a semicolon, ";". You can use the keyboard UP and DOWN keys to scroll the history of previous commands you've run.

Setup

installation, Ubuntu

http://www.postgresql.org/download/linux/ubuntu/ https://help.ubuntu.com/community/PostgreSQL

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Element

Box metrics

elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent
elem.clientLeft, elem.clientTop, elem.clientWidth, elem.clientHeight
elem.getClientRects(), elem.getBoundingClientRect()

	** Find commmonly accessed tables and their use of indexes:

	SELECT relname,seq_tup_read,idx_tup_fetch,cast(idx_tup_fetch AS numeric) / (idx_tup_fetch + seq_tup_read) AS idx_tup_pct FROM pg_stat_user_tables WHERE (idx_tup_fetch + seq_tup_read)>0 ORDER BY idx_tup_pct;

	Returns output like:

	relname \| seq_tup_read \| idx_tup_fetch \| idx_tup_pct
	----------------------+--------------+---------------+------------------------
	schema_migrations \| 817 \| 0 \| 0.00000000000000000000
	user_device_photos \| 349 \| 0 \| 0.00000000000000000000

	--- PSQL queries which also duplicated from https://github.com/anvk/AwesomePSQLList/blob/master/README.md
	--- some of them taken from https://www.slideshare.net/alexeylesovsky/deep-dive-into-postgresql-statistics-54594192

	-- I'm not an expert in PSQL. Just a developer who is trying to accumulate useful stat queries which could potentially explain problems in your Postgres DB.

	------------
	-- Basics --
	------------

	-- Get indexes of tables

	# Elixir has lazily evaluated enumerable objects that allow you
	# to work with enumerable objects like lists either only as needed
	# or infinitely.

	# Start up iex to play around
	$ iex

	# Typical enumeration is done eagerly where the result is computed ASAP
	iex> Enum.map(1..10, fn i -> i * 2 end)
	[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

	$ mix new policy_enforcement_playground
	$ cd policy_enforcement_playground

	# Make a new file lib/authorization.ex
	defmodule Authorization do
	def authorize_first_thing(_user, resource) do
	# Do some authorization here, modifying what gets returned based on the
	# authorization level of the user
	resource
	end

	# The Elixir language is very extensible to allow for future additions or
	# third party developers to take the language in directions that the original
	# authors could not predict.
	#
	# Lets start with understanding what an Elixir macro is
	iex> quote do
	...> 1 + 1
	...> end
	{:+, [context: Elixir, import: Kernel], [1, 1]}

	begin;

	/*
	* Get a list of 200
	*/

	create view bak.ed_renewals_for_zeus as
	select user_id,
	rxcui,
	subscription_id,

	Request URL:https://8wdfb4bdpl.execute-api.us-west-2.amazonaws.com/beta/rpc/login
	Request Method:POST
	Status Code:400
	Remote Address:54.192.136.194:443
	Referrer Policy:no-referrer-when-downgrade

	Response Headers
	access-control-allow-headers:Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token
	access-control-allow-methods:DELETE,GET,HEAD,OPTIONS,PATCH,POST,PUT
	access-control-allow-origin:*