Mr. Sun Sunappnio

Presto Specific

Don’t SELECT *, Specify explicit column names (columnar store)
Avoid large JOINs (filter each table first)
- In PRESTO tables are joined in the order they are listed!!
- Join small tables earlier in the plan and leave larger fact tables to the end
- Avoid cross joins or 1 to many joins as these can degrade performance
Order by and group by take time
- only use order by in subqueries if it is really necessary
When using GROUP BY, order the columns by the highest cardinality (that is, most number of unique values) to the lowest.

Kafka 0.11.0.0 (Confluent 3.3.0) added support to manipulate offsets for a consumer group via cli kafka-consumer-groups command.

List the topics to which the group is subscribed

kafka-consumer-groups --bootstrap-server <kafkahost:port> --group <group_id> --describe

Note the values under "CURRENT-OFFSET" and "LOG-END-OFFSET". "CURRENT-OFFSET" is the offset where this consumer group is currently at in each of the partitions.

Reset the consumer offset for a topic (preview)

	// Creates a new promise that automatically resolves after some timeout:
	Promise.delay = function (time) {
	return new Promise((resolve, reject) => {
	setTimeout(resolve, time)
	})
	}

	// Throttle this promise to resolve no faster than the specified time:
	Promise.prototype.takeAtLeast = function (time) {
	return new Promise((resolve, reject) => {

	# LVDB - LLOOGG Memory DB
	# Copyriht (C) 2009 Salvatore Sanfilippo <[email protected]>
	# All Rights Reserved

	# TODO
	# - cron with cleanup of timedout clients, automatic dump
	# - the dump should use array startsearch to write it line by line
	# and may just use gets to read element by element and load the whole state.
	# - 'help','stopserver','saveandstopserver','save','load','reset','keys' commands.
	# - ttl with milliseconds resolution 'ttl a 1000'. Check ttl in dump!

	Backup:
	docker exec -t -u postgres your-db-container pg_dumpall -c > dump_`date +%d-%m-%Y"_"%H_%M_%S`.sql

	Restore:
	cat your_dump.sql \| docker exec -i your-db-container psql -Upostgres

	npm set registry https://r.npm.taobao.org # 注册模块镜像
	npm set disturl https://npm.taobao.org/dist # node-gyp 编译依赖的 node 源码镜像

	## 以下选择添加
	npm set sass_binary_site https://npm.taobao.org/mirrors/node-sass # node-sass 二进制包镜像
	npm set electron_mirror https://npm.taobao.org/mirrors/electron/ # electron 二进制包镜像
	npm set ELECTRON_MIRROR https://cdn.npm.taobao.org/dist/electron/ # electron 二进制包镜像
	npm set puppeteer_download_host https://npm.taobao.org/mirrors # puppeteer 二进制包镜像
	npm set chromedriver_cdnurl https://npm.taobao.org/mirrors/chromedriver # chromedriver 二进制包镜像
	npm set operadriver_cdnurl https://npm.taobao.org/mirrors/operadriver # operadriver 二进制包镜像

	<?php

	namespace App\Providers;

	use League\Flysystem\Sftp\SftpAdapter;
	use Storage;
	use League\Flysystem\Filesystem;
	use Illuminate\Support\ServiceProvider;

	/**

	// Run this in the F12 javascript console in chrome
	// if a redirect happens, the page will pause
	// this helps because chrome's network tab's
	// "preserve log" seems to technically preserve the log
	// but you can't actually LOOK at it...
	// also the "replay xhr" feature does not work after reload
	// even if you "preserve log".

	window.addEventListener("beforeunload", function() { debugger; }, false)

	# to generate your dhparam.pem file, run in the terminal
	openssl dhparam -out /etc/nginx/ssl/dhparam.pem 2048