Mohit Munjani mohitmun

Comments on optimizations around string concatenation.

Note: The code links are to CPython 3.8.5, the most recent release when this was written.

I was recently asked about a performance optimization in CPython around using += and + for string objects. As some people may already know, if you use += or + a string, it can sometimes be just as fast as ''.join. The question was to explain when that optimization couldn't be performed.

We will be going through the following example scenarios:

This TRIGGER function calls PosgreSQL's NOTIFY command with a JSON payload. You can listen for these calls and then send the JSON payload to a message queue (like AMQP/RabbitMQ) or trigger other actions.

Create the trigger with notify_trigger.sql.

When declaring the trigger, supply the column names you want the JSON payload to contain as arguments to the function (see create_triggers.sql)

The payload returns a JSON object:

After updating pg_hba.conf or postgresql.conf, the server needs the config needs to be reloaded. The easiest way to do this is by restarting the postgres service:

service postgresql restart

When the service command is not available (no upstart on Synology NAS, for example), there are some more creative ways to reload the config. Note this first one needs to be done under the user that runs postgres (usually the user=postgres).

user#  sudo su postgres
postgres#  pg_ctl reload

Gmail and GitHub

How to filter emails from GitHub in Gmail and flag them with labels.

The labels in this document are just examples.

Pull Request

Filter	Label

Vim without NERD tree or CtrlP

I used to use NERD tree for quite a while, then switched to CtrlP for something a little more lightweight. My setup now includes zero file browser or tree view, and instead uses native Vim fuzzy search and auto-directory switching.

Fuzzy Search

There is a super sweet feature in Vim whereby you can fuzzy find your files using **/*, e.g.:

:vs **/*<partial file name><Tab>

How to recover lost Python source code if it's still resident in-memory

I screwed up using git ("git checkout --" on the wrong file) and managed to delete the code I had just written... but it was still running in a process in a docker container. Here's how I got it back, using https://pypi.python.org/pypi/pyrasite/ and https://pypi.python.org/pypi/uncompyle6

Attach a shell to the docker container

Install GDB (needed by pyrasite)

apt-get update && apt-get install gdb

	"A small script to measure typing speed
	"Shows speed in bottom bar when you leave insert mode
	"Run :messages to see all recent speeds
	"This script was a hack thrown together in 10-15 minutes and has not been well tested yet.
	function! s:insertEnterTypespeed()
	let b:startTime = localtime()
	endfunction
	function! s:insertLeaveTypespeed()
	let chars = strlen(@.)
	if chars

	CS
	DMKS
	Heterogeneous programming
	OpenCl
	https://en.wikipedia.org/wiki/OpenCL
	Compilers
	Design patterns
	https://en.wikipedia.org/wiki/Worse_is_better
	File System
	File Descriptors

	from http.client import HTTPSConnection
	from base64 import b64encode
	from json import loads
	from sys import exit, argv, stderr
	from time import sleep

	import urllib3

	# Settings
	PRINT_REPOS = True

	# get total requests by status code
	awk '{print $9}' /var/log/nginx/access.log \| sort \| uniq -c \| sort -rn

	# get top requesters by IP
	awk '{print $1}' /var/log/nginx/access.log \| sort \| uniq -c \| sort -rn \| head \| awk -v OFS='\t' '{"host " $2 \| getline ip; print $0, ip}'

	# get top requesters by user agent
	awk -F'"' '{print $6}' /var/log/nginx/access.log \| sort \| uniq -c \| sort -rn \| head

	# get top requests by URL