hopsoft

sudo apt-get update
sudo apt-get install libjemalloc-dev
RUBY_CONFIGURE_OPTS='--with-jemalloc' rbenv install 2.6.3

# test (look for jemalloc warnings)
MALLOC_CONF=invalid_flag:foo ruby -v

ProGM

Arel Cheatsheet on Steroids

A (more) complete cheatsheet for Arel, including NamedFunction functions, raw SQL and window functions.

Tables

posts = Arel::Table.new(:posts)
posts = Post.arel_table # ActiveRecord

Table alias

mabenson00

# Basic key operators to query the JSON objects :

# #> : Get the JSON object at that path (if you need to do something fancy)
# -> : Get the JSON object at that path (if you don't)
# ->> : Get the JSON object at that path as text
# {obj, n} : Get the nth item in that object

# https://www.postgresql.org/docs/9.4/functions-json.html#FUNCTIONS-JSONB-OP-TABLE
# Date 
# date before today