Matt Button BRMatt

ANNOUNCEMENT

I have moved this over to the Tech Interview Cheat Sheet Repo and has been expanded and even has code challenges you can run and practice against!

\

	#!/bin/bash

	cmd-hello() {
	declare desc="Displays a friendly hello"
	declare firstname="$1" lastname="$2"
	echo "Hello, $firstname $lastname."
	}

	cmd-help() {
	declare desc="Shows help information for a command"

	(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).

	This tool is used to compare microbenchmarks across two versions of code. It's
	paranoid about nulling out timing error, so the numbers should be meaningful.
	It runs the benchmarks many times, scaling the iterations up if the benchmark
	is extremely short, and it nulls out its own timing overhead while doing so. It
	reports results graphically with a text interface in the terminal.

	You first run it with --record, which generates a JSON dotfile with runtimes
	for each of your benchmarks. Then you change the code and run again with
	--compare, which re-runs and generates comparison plots between your recorded
	and current times. In the example output, I did a --record on the master

	WITH table_scans as (
	SELECT relid,
	tables.idx_scan + tables.seq_scan as all_scans,
	( tables.n_tup_ins + tables.n_tup_upd + tables.n_tup_del ) as writes,
	pg_relation_size(relid) as table_size
	FROM pg_stat_user_tables as tables
	),
	all_writes as (
	SELECT sum(writes) as total_writes
	FROM table_scans