Alexander sitesmake

N+1 query problem

ORMs make it easy to a query per loop iteration, which we want to avoid

eager_load

single query (left outer join)
can reference the other table's columns in where

preload

a few queries (one per table)
typically faster

Types of index scans

Indexes

Sequential Scan:

Read every row in the table
No reading of index. Reading from indexes is also expensive.

Это старая версия урока, которая больше не обновляется. Новая версия расположения тут: https://github.com/codedokode/pasta/blob/master/db/patterns-oop.md

Паттерны работы с базой данных

Разберемся, как правильно с применением ООП сохранять и загружать данные из базы. Существуют такие подходы:

примитивный подход с использованием PDO/массивов
ActiveRecord http://design-pattern.ru/patterns/active-record.html

sudo su postgres
psql

update pg_database set datistemplate=false where datname='template1';
drop database Template1;
create database template1 with owner=postgres encoding='UTF-8' lc_collate='en_US.utf8' lc_ctype='en_US.utf8' template template0;
update pg_database set datistemplate=true where datname='template1';

Installing Postgres via Brew

Pre-Reqs

Brew Package Manager

In your command-line run the following commands:

brew doctor
brew update

URL	HTTP Verb	Action
/photos/	GET	index
/photos/new	GET	new
/photos	POST	create
/photos/:id	GET	show
/photos/:id/edit	GET	edit
/photos/:id	PATCH/PUT	update
/photos/:id	DELETE	destroy

	HTTP status code symbols for Rails

	Thanks to Cody Fauser for this list of HTTP responce codes and their Ruby on Rails symbol mappings.

	Status Code Symbol
	1xx Informational
	100 :continue
	101 :switching_protocols
	102 :processing

	// Use Gists to store code you would like to remember later on
	console.log(window); // log the "window" object to the console