Daniel Durante durango

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.

Go Cheat Sheet

Index

Declarations

Go Cheat Sheet

Index

Declarations

WAL-G PITR

This gist summarises a way to simulate point-in-time recovery (PITR) using WAL-G. Most of the material is adapted from Creston's tutorial.

Setup

First we initialize a database cluster

pg_ctl init -D cluster

Neo4j directed path through multiple relationships with property filter

From Stackoverflow Question

Being new to Cypher and Neo4j, I am having trouble constructing my query for my use-case. I am building a simple ACL (access control list) and am looking for a path through permission relationships an up a hierarchy as well. A picture may better explain it:

Key:

List of Cryptocurrency exchanges with Websocket API

	Mozilla Public License, version 2.0

	1. Definitions

	1.1. "Contributor"

	means each individual or legal entity that creates, contributes to the
	creation of, or owns Covered Software.

	1.2. "Contributor Version"

	import React, { useReducer, useEffect, useRef } from 'react';
	import firebase from 'firebase/app';
	import equal from 'deep-equal';

	function filterKeys(raw, allowed) {
	if (!raw) {
	return raw;
	}
	let s = new Set(allowed);
	return Object.keys(raw)

	-- 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%'

	package main

	import (
	"fmt"
	)

	type MyEmitter map[string]chan string

	func main() {
	myEmitter := MyEmitter{}