felixge

SELECT version();
                                                             version
----------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 11.5 (Debian 11.5-1.pgdg90+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516, 64-bit
(1 row)

-- Why is this returning true?
-- I think { and [ are considered to sort equally on this machine's `en_US` collation, 
-- so the result is the same as `'{' < '{a'`
SELECT '{' < '[a' COLLATE "en_US";

felixge

SHOW LC_COLLATE;
 lc_collate
-------------
 en_US.UTF-8
(1 row)

EXPLAIN ANALYZE
SELECT g::text FROM generate_series(1, 10000) g ORDER BY 1;
                                                          QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------

felixge

package main

import "fmt"

func main() {
	f1 := &Foo{}
	f2 := &Foo{}
	fmt.Printf("%p = %p\n", f1, f2)

	b1 := &Bar{}

felixge

package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"net"
	"os"
	"sync"

felixge

encoded_in = "\x00\x00\x00\x03aaa\x00\x00\x00\x06Binary\x02\x00\x00\x00\fP\x00\x84A\xEB\xF9~?\x966\xE7\x8A\x00\x00\x00\x03ccc\x00\x00\x00\x06String\x01\x00\x00\x00\x04test\x00\x00\x00\x03zzz\x00\x00\x00\x06Number\x01\x00\x00\x00\a0230.01\x00\x00\x00\x10\xC3\xB6ther_encodings\x00\x00\x00\x06String\x01\x00\x00\x00\x05T\xC3\xBCst"

class EncodedMessage
  attr_accessor :data
  attr_accessor :md5

  def initialize(data, md5)
    @data = [data].pack('a*')
    @md5 = md5
    # TODO(fg) verify md5

felixge

*
!**/*.go

felixge

psql (9.6.3, server 10.1)
WARNING: psql major version 9.6, server major version 10.
         Some psql features might not work.
Type "help" for help.

postgres=# CREATE FUNCTION date_round(base_date timestamptz, round_interval INTERVAL) RETURNS timestamptz AS $BODY$
postgres$# SELECT TO_TIMESTAMP((EXTRACT(epoch FROM $1)::INTEGER + EXTRACT(epoch FROM $2)::INTEGER / 2)
postgres$#                 / EXTRACT(epoch FROM $2)::INTEGER * EXTRACT(epoch FROM $2)::INTEGER)
postgres$# $BODY$ LANGUAGE SQL STABLE;
CREATE FUNCTION

felixge

Load the data

See http://randyzwitch.com/mapd-pjm-electricity-data/ for the data and pythons script to create hourly_loads.csv (146MB) and https://news.ycombinator.com/item?id=16458105 for discussion.

CREATE TABLE hourly_loads (
	actual_date date,
	zone_name text,

felixge

See my HN comment on the post The 3-minute SQL indexing quiz: Can you spot the five most common mistakes? . Do you agree that my answer ("Not enough information: Definite answer cannot be given") is correct? See proof in psql.txt below.

Question 5

This question is different. First consider the following index and query:

CREATE INDEX tbl_idx ON tbl (a, date_column)
SELECT date_column, count(*)
  FROM tbl

felixge

#!/usr/bin/env bash
# see https://github.com/docker/for-mac/issues/668
set -eu
cd ~/Library/Containers/com.docker.docker/Data/database/
git reset --hard
echo false > com.docker.driver.amd64-linux/disk/full-sync-on-flush
git add com.docker.driver.amd64-linux/disk/full-sync-on-flush 
git commit -s -m "Unfucked docker"