jessieay

ActiveRecord cheat sheet / EXAMPLES

INSTALL 
=======  
$ gem install activerecord
in GEMFILE: gem ‘activerecord’

REQUIRE 
=======  
require ‘active_record’

rgreenjr

-- 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%' 

rboyd

(defn rand-str [len]
  (apply str (take len (repeatedly #(char (+ (rand 26) 65))))))

tsdh

(defn parent-children-map
  "Converts a vector of [child parent] edges into a map where every entry has
  the form [parent set-of-children].

  Examples:

  (parent-children-map [[0, 2], [3, 0], [1, 4], [2, 4]])
  ;=> {4 #{1 2}, 0 #{3}, 2 #{0}}

  (parent-children-map [[10 1] [1 4] [6 1] [8 6] [9 5] [2 4]

richhickey

(require '[clojure.core.async :as a])

(def xform (comp (map inc)
              (filter even?)
              (dedupe)
              (flatmap range)
              (partition-all 3)
              (partition-by #(< (apply + %) 7))
              (flatmap flatten)
              (random-sample 1.0)

ptaoussanis

(comment ; Fun with transducers, v2

  ;; Still haven't found a brief + approachable overview of Clojure 1.7's new
  ;; transducers in the particular way I would have preferred myself - so here goes:

  ;;;; Definitions
  ;; Looking at the `reduce` docstring, we can define a 'reducing-fn' as:
  (fn reducing-fn ([]) ([accumulation next-input])) -> new-accumulation
  ;; (The `[]` arity is actually optional; it's only used when calling
  ;; `reduce` w/o an init-accumulator).

stathissideris

(defn tree-seq-depth
  "Returns a lazy sequence of vectors of the nodes in a tree and their
  depth as [node depth], via a depth-first walk.  branch? must be a fn
  of one arg that returns true if passed a node that can have
  children (but may not).  children must be a fn of one arg that
  returns a sequence of the children. Will only be called on nodes for
  which branch? returns true. Root is the root node of the tree."
  [branch? children root]
  (let [walk (fn walk [depth node]
               (lazy-seq

logger.ex

defmodule Saturn.Logger do
  use Timex
  require Logger
  alias Plug.Conn
  @behaviour Plug

  def init(opts) do
    Keyword.get(opts, :log, :info)
  end

shaunlebron

Comparing ES7 and core.async

ES7	core.async
async function() {...}	(fn [] (go ...))
await ...	(<! ...)
await* or Promise.all(...)	(doseq [c ...] (<! c))

brock

# This is just a cheat sheet:

# On production
sudo -u postgres pg_dump database | gzip -9 > database.sql.gz

# On local
scp -C production:~/database.sql.gz
dropdb database && createdb database
gunzip < database.sql.gz | psql database